![C PROGRAMMING
15
* Pointer to a variable. *a;
? : Conditional Expression.
If Condition is true ? then value X : otherwise
value Y
Operators Precedence in C
Operator precedence determines the grouping of terms in an expression and decides how an
expression is evaluated. Certain operators have higher precedence than others; for example, the
multiplication operator has a higher precedence than the addition operator.
For example, x = 7 + 3 * 2; here, x is assigned 13, not 20 because operator * has a higher
precedence than +, so it first gets multiplied with 3*2 and then adds into 7.
Here, operators with the highest precedence appear at the top of the table, those with the lowest
appear at the bottom. Within an expression, higher precedence operators will be evaluated first.
Show Examples
Category Operator Associativity
Postfix () [] -> . ++ - - Left to right
Unary + - ! ~ ++ - - (type)* & sizeof Right to left
Multiplicative * / % Left to right
Additive + - Left to right
Shift << >> Left to right
Relational < <= > >= Left to right
Equality == != Left to right
Bitwise AND & Left to right
Bitwise XOR ^ Left to right](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-16-320.jpg)
![C PROGRAMMING
Precedence of Operators in C
The precedence of operator species that which operator will be evaluated first and next. The
associativity specifies the operator direction to be evaluated; it may be left to right or right to left.
Let's understand the precedence by the example given below:
1. int value=10+20*10;
The value variable will contain 210 because * (multiplicative operator) is evaluated before +
(additive operator).
The precedence and associativity of C operators is given below:
Category Operator Associativity
Postfix () [] -> . ++ - - Left to right
Unary + - ! ~ ++ - - (type)* & sizeof Right to left
Multiplicative * / % Left to right
Additive + - Left to right
Shift << >> Left to right
Relational < <= > >= Left to right
Equality == != Left to right
Bitwise AND & Left to right
Bitwise XOR ^ Left to right
Bitwise OR | Left to right
Logical AND && Left to right
Logical OR || Left to right
Conditional ?: Right to left
Assignment = += -= *= /= %=>>= <<= &= ^= |= Right to left
Comma , Left to right
17](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-18-320.jpg)
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1int arrayone[10];
Two-Dimensional Array
The two-dimensional array can be defined as an array of arrays. The 2D array is organized as
matrices which can be represented as the collection of rows and columns. The elements of the
array are accessed using their intersection coordinates.
int arraytwo[10][5];
1
Multi-Dimensional Array
The multi-dimensional array can be defined as an array of arrays. The 3D array is organized as 3D
matrix which can be represented as the collection of multiple rows and columns. The elements of
the array are accessed using their 3D intersection coordinates.
1int arraythree[10][10][10];
Why do we need it? In this article, you will learn about the data structure array and its types
and why is it a widely used data structure. Let’s get into it.
An Array is a sequential collection of elements, of the same data type. They are stored
sequentially in memory. An Array is a data structure that holds a similar type of elements. The
array elements are not treated as objects in c like they are in java.
Imagine you are at a musical instrument store and I tell you to arrange all the keyboards under
the brand Casio at one place one above the other. This sequential collection of records is called](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-49-320.jpg)
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49
an Array. An array is a sequential collection of elements of the same data type. In our example
above, Casio is the data type and all the keyboards you collected are of the brand Casio. All the
elements in an array are addressed by a common name.
There are two types of arrays:
1. Single dimensional array
2. Array Initialization
3. Accessing Array at any Point
4. Multidimensional array
SINGLE DIMENSIONAL ARRAY
The syntax for declaring a Single Dimensional Array:
Datatype arrayName[arraySize];
We have a data type that can be any of the basic data types like int, float or double.
Array Name is the name of the array and we declare the size of the array.
In our above example, the array will be,
Casio keyboardArray[100];
Let’s consider another example:
int test[30];
The array test will hold the elements of type int and will have a size 30.
ARRAY SIZE:
Array size is given at the time of declaration of the array. Once the size of the
array is given it cannot be changed. The compiler then allocates that much
memory space to the array.
Consider the Example:
int test[20];](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-50-320.jpg)
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50
In the example above, we have an array test, of type int. We have given the array
size to be 20. This means that 20 consecutive memory locations will be left free for
the array in the memory.
ARRAY INDEX AND INITIALIZATION
A number associated with each position in an array and this number is called the array index. Its
starts from 0 and to the last element, that is the size of the array minus one. The minus one is
there because we start counting from zero and not one. Array indices always begin fromzero.
Consider this example, this is the age array.
Here the array contains the values 12,41,3,13,7 and the indices are 0,1,2,3,4. If we want to
represent an element at index 4 it is represented as age[4] and the value 7 will be displayed.
By default, the array contains all zero values.
Array initialization is done at the time of declaration. This can also be carried out later if the
user enters the array value as and when needed.
INITIALIZATION DURING DECLARATION:
An array can be initialized during declaration. This is done by specifying the array elements at
the time of declaration. Here the array size is also fixed and it is decided by us.
Consider the code,
#include<stdio.h>
int main()
{
int arr[] = { 10, 20, 30, 40 } ;
return 0; }
EXPLANATION:](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-51-320.jpg)
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51
In the above example, we create an array of type int and with the name arr. We directly specify
the array elements. The size of the array is decided by counting the number of elements in our
array. In this case, the size is 4.
INITIALIZATION BY USER:
In this method, we let the user decide the size of the array. In this case, we need a variable to hold
the size of the array and a for loop to accept the elements of the array. We assign a random size
at the time of declaration and use only as needed. The size at the start is usually at the higher
side. We have a variable i to control the for loop.
Consider the example,
#include<stdio.h>
int main()
{
int arr[50],n,i ;
printf("Enter the size of array:n");
scanf(“%d ”,n);
printf("Enter the elements of array:n");
for(i=0;i<n;i++)
{
Scanf(“%d ”,arr[i]);
}
return 0;
}
OUTPUT:
EXPLANATION:](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-52-320.jpg)
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53
DISPLAYING THE ARRAY:
Displaying the array also requires the for-loop. We traverse to the entire array and
display the elements of the array.
Here is an example,
#include<stdio.h>
int main()
{
int arr[50],n,i ;
printf("Enter the size of array:n");
scanf(“%d ”,n);
printf("Enter the elements of array:n");
for(i=0;i<n;i++)
{
Scanf(“%d ”,arr[i]);
}
printf("Array Elements are:n");
for(i=0;i<n;i++)
{
Printf(“%d ”,arr[i]);
}
return 0;
}
OUTPUT:](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-54-320.jpg)
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54
EXPLANATION:
In the above program, we declare an array of size 50. We then ask the user to enter the number of
elements he wishes to enter in this array. We then accept the array elements entered by the user.
We then use a for loop again to display the array elements.
ACCESSING THE ARRAY AT ANY POINT:
Accessing array elements is simple and is done by using the array index. Have a look at the
code below.
#include<stdio.h>
int main()
{
int arr[5],i ;
arr[4]=2;
arr[2]=17;
arr[0]=17;
printf("Array elements are: n");
for(i=0;i<5;i++)
{
printf(“%d ”,arr[i]);
}
return 0;](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-55-320.jpg)
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55
}
OUTPUT:
EXPLANATION:
In the program above, we have an array of size 5. We enter elements at different locations
using array index. We print the array to get the above output.
By Default, all the array elements are zero. What happens if we cross the array size?
In c, if we try to access the elements out of bound, error may not be shown by the compiler but
we will not get proper output.
MULTI-DIMENSIONAL ARRAY:
Arrays of arrays are multi-dimensional arrays. This is because each element in a multi-
dimensional array has an array of its own. We need n for loops to iterate through a
multidimensional array depending on the dimensions.
SYNTAX FOR DECLARING MULTI_DIMENSIONAL ARRAYS:
Datatype arrayname[size1][size2]…..[size n];
Consider the example,
int a[10][20];
The size of the above array will be 10*20 that is 200 elements.
Similarly, we can have two or three or even more dimensional arrays.
Each dimension requires one for loop. So, the two-dimensional array requires two- and three-
dimensional array requires three.
Consider the code:
#include<stdio.h>
int main()
{](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-56-320.jpg)
![C PROGRAMMING
56
int arr[3][2] = {{0,1}, {2,3}, {4,5}};
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 2; j++)
{
printf( "Element: %d n”,arr[i][j]);
}
}
return 0;
}
EXPLANATION:
In the above code, we display a 3*2 matrix. This array has 3 rows and 2 columns. We have 2 for
loops. Each responsible for one dimension of the array. The outer for loop takes care of rows and
inner of columns.
Similarly, we can write a code for three-dimensional array and there will be three for loops and
each dimension will be controlled by one for loop.](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-57-320.jpg)
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57
Strings
The string is defined as a one-dimensional array of characters terminated by a null character. The
character array or the string is used to store text such as word or sentences. Each character in the
array occupies one byte of memory, and the last character must always be0.
Two types of strings are:
char array
string literal
The String functions available in C language are as follows
Function Functionality
strlen() Returns the length of the String
strcpy() Copies String from Source to Destination
strcat() Joins two Strings and stores result in first
strcmp() Compares the given two Strings
strrev() Reverses the String
strlwr() Converts String to Lower case
strupr() Converts String to Upper case
strchr() String scanning function
strncat() Concatenates String with the part of another
srtncmp() Compares the parts of two Strings
strncpy() Copies a part of the String
//Example
1#include<stdio.h>
2#include<string.h>
3int main( )
4{
5
6
7
8
9
10}
//Output
int len;
char text[10]="saveetha" ;
length = strlen(array) ;
printf ( "string length is = %d n" , length ) ;
return 0;
string length is = 7
Functions](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-58-320.jpg)
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71
11. }
12. }
13. printf("%d ",a); // 11 will be printed since the scope of a = 20 is ended.
14. }
Output:
11 20 20 20 11
Static
o The variables defined as static specifier can hold their value between the multiple function calls.
o Static local variables are visible only to the function or the block in which they are defined.
o A same static variable can be declared many times but can be assigned at only one time.
o Default initial value of the static integral variable is 0 otherwise null.
o The visibility of the static global variable is limited to the file in which it has declared.
o The keyword used to define static variable is static.
Example 1
1. #include<stdio.h>
2. static char c;
3. static int i;
4. static float f;
5. static char s[100];
6. void main ()
7. {
8. printf("%d %d %f %s",c,i,f); // the initial default value of c, i, and f will be printed.
9. }
Output:
0 0.000000 (null)
Example 2
1. #include<stdio.h>
2. void sum()
3. {
4. static int a = 10;
5. static int b = 24;
6. printf("%d %d n",a,b);
7. a++;](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-72-320.jpg)
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76
#include <stdio.h>
int main( int argc, char *argv[] ) {
if( argc == 2 ) {
printf("The argument supplied is %sn", argv[1]);
}
else if( argc > 2 ) {
printf("Too many arguments supplied.n");
}
else {
printf("One argument expected.n");
}
}
$./a.out testing
The argument supplied is testing
6 time.h This header file contains all the time-related functions.
7 ctype.h This header file contains all character handling functions.
8 stdarg.h Variable argument functions are defined in this header file.
9 signal.h All the signal handling functions are defined in this header file.
10 setjmp.h This file contains all the jump functions.
11 locale.h This file contains locale functions.
12 errno.h This file contains error handling functions.
13 assert.h This file contains diagnostics functions.
Command line arguments:
It is possible to pass some values from the command line to your C programs when they are
executed. These values are called command line arguments and many times they are
important for your program especially when you want to control your program from outside
instead of hard coding those values inside the code.
The command line arguments are handled using main() function arguments where argc refers to
the number of arguments passed, and argv[] is a pointer array which points to each argument
passed to the program. Following is a simple example which checks if there is any argument
supplied from the command line and take action accordingly −
When the above code is compiled and executed with single argument, it produces the following
result.](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-77-320.jpg)
![C PROGRAMMING
77
$./a.out testing1 testing2
Too many arguments supplied.
$./a.out
One argument expected
#include <stdio.h>
int main( int argc, char *argv[] ) {
printf("Program name %sn", argv[0]);
if( argc == 2 ) {
printf("The argument supplied is %sn", argv[1]);
}
else if( argc > 2 ) {
printf("Too many arguments supplied.n");
}
else {
printf("One argument expected.n");
}
}
$./a.out "testing1 testing2"
Program name ./a.out
The argument supplied is testing1 testing2
When the above code is compiled and executed with a two arguments, it produces the following
result.
When the above code is compiled and executed without passing any argument, it produces the
following result.
It should be noted that argv[0] holds the name of the program itself and argv[1] is a pointer to
the first command line argument supplied, and *argv[n] is the last argument. If no arguments are
supplied, argc will be one, and if you pass one argument then argc is set at 2.
You pass all the command line arguments separated by a space, but if argument itself has a
space then you can pass such arguments by putting them inside double quotes "" or single
quotes ''. Let us re-write above example once again where we will print program name and we
also pass a command line argument by putting inside double quotes −
When the above code is compiled and executed with a single argument separated by space but
inside double quotes, it produces the following result.](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-78-320.jpg)
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86
C Pointers & Arrays with Examples
Traditionally, we access the array elements using its index, but this method can be
eliminated by using pointers. Pointers make it easy to access each array element.
#include <stdio.h>
int main()
{
int a[5]={1,2,3,4,5}; //array initialization
int *p; //pointer declaration
/*the ptr points to the first element of the array*/
p=a; /*We can also type simply ptr==&a[0] */
printf("Printing the array elements using pointern");
for(int i=0;i<5;i++) //loop for traversing array elements
{
printf("n%x",*p); //printing array elements
p++; //incrementing to the next element, you can
also write p=p+1
}
return 0;
}
Output
1
2
3
4
5
Addingaparticularnumbertoapointerwillmovethepointerlocationtothevalue
obtainedbyanadditionoperation.Supposepisapointerthatcurrentlypointstothe
memorylocation0ifweperformfollowingadditionoperation,p+1thenitwillexecuteinthis
manner:
Pointer Addition/Increment
Sincepcurrentlypointstothelocation0afteradding1,thevaluewillbecome1,andhence
the pointer will point to the memory location 1.](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-87-320.jpg)
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87
C Pointers and Strings with Examples
Astringisanarrayofcharobjects,endingwithanullcharacter‘0’.Wecanmanipulate
stringsusingpointers.ThispointerinCexampleexplainsthissection
#include <stdio.h>
#include <string.h>
int main()
{
char str[]="Hello Guru99!";
char *p;
p=str;
printf("First character is:%cn",*p); p
=p+1;
printf("Next character is:%cn",*p);
printf("Printing all the characters in a stringn");
p=str; //reset the pointer
for(int i=0;i<strlen(str);i++)
{
printf("%cn",*p);
p++;
}
return 0;
}
Output
First character is:H
Next character is:e
Printing all the characters in a string
H
e
l
l
o
G
u
r
u
9
9
!
Anotherwaytodealstringsiswithanarrayofpointerslikeinthefollowingprogram:
#include <stdio.h>
int main(){
char *materials[ ] = { "iron", "copper", "gold"};
printf("Please remember these materials :n");
int i ;
for (i = 0; i < 3; i++) {
printf("%sn", materials[ i ]);}
return 0;}](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-88-320.jpg)
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90
Here, struct is the keyword; employee is the name of the structure; id, name,
and salary are the members or fields of the structure. Let's understand it by the
diagram given below:
Declaring structure variable
We can declare a variable for the structure so that we can access the member of the structure
easily. There are two ways to declare structure variable:
1. By struct keyword within main() function
2. By declaring a variable at the time of defining the structure.
1st way:
Let's see the example to declare the structure variable by struct
keyword. It should be declared within the main function.
struct employee
{ int id;
char name[50];
float salary;
};
Now write given code inside the main() function.
1. struct employee e1, e2;](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-91-320.jpg)
![C PROGRAMMING
91
The variables e1 and e2 can be used to access the values stored in the structure.
Here, e1 and e2 can be treated in the same way as the objects in C++ and Java.
2nd way:
Let's see another way to declare variable at the time of defining the structure.
struct employee
{ int id;
char name[50];
float salary;
}e1,e2;
Which approach is good
If number of variables are not fixed, use the 1st approach. It provides you the
flexibility to declare the structure variable many times.
Accessing members of the structure
There are two ways to access structure members:
1. By . (member or dot operator)
2. By -> (structure pointer operator)
Let's see the code to access the id member of p1 variable by. (member)
operator.
p1.id
C Structure example
Let's see a simple example of structure in C language.
1. #include<stdio.h>
2. #include <string.h>
3. struct employee
4. { int id;
5. char name[50];
6. }e1; //declaring e1 variable for structure](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-92-320.jpg)
![C PROGRAMMING
92
employee 1 id : 101
employee 1 name : Sonoo Jaiswal
7. int main( )
8. {
9. //store first employee information
10. e1.id=101;
11. strcpy(e1.name, "Sonoo Jaiswal");//copying string into char array
12. //printing first employee information
13. printf( "employee 1 id : %dn", e1.id);
14. printf( "employee 1 name : %sn", e1.name);
15. return 0;
16. }
Output:
Let's see another example of the structure in C language to store many employees
information.
1. #include<stdio.h>
2. #include <string.h>
3. struct employee
4. { int id;
5. char name[50];
6. float salary;
7. }e1,e2; //declaring e1 and e2 variables for structure
8. int main( )
9. {
10. //store first employee information
11. e1.id=101;
12. strcpy(e1.name, "Sonoo Jaiswal");//copying string into char array
13. e1.salary=56000;
14.
15. //store second employee information
16. e2.id=102;
17. strcpy(e2.name, "James Bond");
18. e2.salary=126000;
19.
20. //printing first employee information](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-93-320.jpg)
![C PROGRAMMING
94
Now, we can create the variables of type unsigned int by writing the following
statement:
unit a, b;
instead of writing: unsigned int a, b;
Let's understand through a simple example.
1. #include <stdio.h>
2. int main()
3. {
4. typedef unsigned int unit;
5. unit i,j;
6. i=10;
7. j=20;
8. printf("Value of i is :%d",i);
9. printf("nValue of j is :%d",j);
10. return 0;
11. }
Output
Value of i is :10
Value of j is :20
Using typedef with structures
Consider the below structure declaration:
struct student
{
char name[20];
int age;](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-95-320.jpg)
![C PROGRAMMING
95
};
struct student s1;
In the above structure declaration, we have created the variable of student type by
writing the following statement:
struct student s1;
The above statement shows the creation of a variable, i.e., s1, but the statement is
quite big. To avoid such a big statement, we use the typedef keyword to create
the variable of type student.
struct student
{
char name[20];
int age;
};
typedef struct student stud;
stud s1, s2;
In the above statement, we have declared the variable stud of type struct student.
Now, we can use the stud variable in a program to create the variables of
type struct student.
The above typedef can be written as:
typedef struct student
{
char name[20];
int age;
} stud;
stud s1,s2;
From the above declarations, we conclude that typedef keyword reduces the length
of the code and complexity of data types. It also helps in understanding the
program.
Let's see another example where we typedef the structure declaration.](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-96-320.jpg)
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96
#include <stdio.h>
typedef struct student
{
char name[20];
int age;
}stud;
int main()
{
stud s1;
printf("Enter the details of student s1: ");
printf("nEnter the name of the student:");
scanf("%s",&s1.name);
printf("nEnter the age of student:");
scanf("%d",&s1.age);
printf("n Name of the student is : %s", s1.name);
printf("n Age of the student is : %d", s1.age);
return 0;
}
Enter the details of student s1:
Enter the name of the student: Peter
Enter the age of student: 28
Name of the student is : Peter
Age of the student is : 28
Using typedef with pointers
We can also provide another name or alias name to the pointer variables with the help of the
typedef.
For example, we normally declare a pointer, as shown below:](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-97-320.jpg)
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97
1. int* ptr;
We can rename the above pointer variable as given below:
1. typedef int* ptr;
In the above statement, we have declared the variable of type int*. Now, we can
create the variable of type int* by simply using the 'ptr' variable as shown in the
below statement:
1. ptr p1, p2 ;
In the above statement, p1 and p2 are the variables of type 'ptr'.
C Array of Structures
Why use an array of structures?
Consider a case, where we need to store the data of 5 students. We can store it by using the
structure as given below.
1. #include<stdio.h>
2. struct student
3. {
4. char name[20];
5. int id;
6. float marks;
7. };
8. void main()
9. {
10. struct student s1,s2,s3;
11. int dummy;
12. printf("Enter the name, id, and marks of student 1 ");
13. scanf("%s %d %f",s1.name,&s1.id,&s1.marks);
14. scanf("%c",&dummy);](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-98-320.jpg)
![C PROGRAMMING
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Let's see an example of an array of structures that stores information of 5
students and prints it.
#include<stdio.h>
#include <string.h>
struct student{
int rollno;
char name[10];
};
int main(){
int i;
struct student st[5];
printf("Enter Records of 5 students");
for(i=0;i<5;i++){
printf("nEnter Rollno:");
scanf("%d",&st[i].rollno);
printf("nEnter Name:");
scanf("%s",&st[i].name);
}
printf("nStudent Information List:");
for(i=0;i<5;i++){
printf("nRollno:%d, Name:%s",st[i].rollno,st[i].name);](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-100-320.jpg)
![C PROGRAMMING
100
Enter Records of 5 students
Enter Rollno:1
Enter Name:Sonoo
Enter Rollno:2
Enter Name:Ratan
Enter Rollno:3
Enter Name:Vimal
Enter Rollno:4
Enter Name:James
Enter Rollno:5
Enter Name:Sarfraz
Student Information List:
Rollno:1, Name:Sonoo
Rollno:2, Name:Ratan
Rollno:3, Name:Vimal
Rollno:4, Name:James
Rollno:5, Name:Sarfraz
}
return 0;
}
Output:
Passing structure to function
Just like other variables, a structure can also be passed to a function. We
may pass the structure members into the function or pass the structure
variable at once. Consider the following example to pass the structure
variable employee to a function display() which is used to display the
details of an employee.
#include<stdio.h>
struct address
{
char city[20];
int pin;
char phone[14];
};
struct employee
{
char name[20];
struct address add;
};](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-101-320.jpg)
![C PROGRAMMING
102
4
5
6
7
8};
int Id;
char Name[25];
int Age;
long Salary;
9void main()
10{
11
12
13
14
15
16
17
18
19
20
21
22
23
24}
//Output
union Employee E;
printf("nEnter Employee Id : ");
scanf("%d",&E.Id);
printf("nEnter Employee Name : ");
scanf("%s",&E.Name);
printf("nEnter Employee Age : ");
scanf("%d",&E.Age);
printf("nEnter Employee Salary : ");
scanf("%ld",&E.Salary);
printf("nnEmployee Id : %d",E.Id);
printf("nEmployee Name : %s",E.Name);
printf("nEmployee Age : %d",E.Age);
printf("nEmployee Salary : %ld",E.Salary);
Enter Employee Id : 102191
Enter Employee Name : Karan
Enter Employee Age : 29
Enter Employee Salary : 45000
Employee Id : 102011
Employee Name : Ajay
Employee Age : 26
Employee Salary : 45000
Accessing members of union using pointers
We can access the members of the union through pointers by using the (->) arrow operator.
Let's understand through an example.](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-103-320.jpg)
![C PROGRAMMING
108
#include;
void main( )
{
FILE *fp; // file pointer
char ch;
fp = fopen("file_handle.c","r");
while ( 1 )
{
ch = fgetc ( fp ); //Each character of the file is read and
stored in the character file.
if ( ch == EOF )
break;
printf("%c",ch);
}
fclose (fp );
}
13. }
14. fclose (fp ) ;
15. }
Output
The content of the file will be printed.
Closing File: fclose()
The fclose() function is used to close a file. The file must be closed after performing
all the operations on it. The syntax of fclose() function is given below:
int fclose( FILE *fp );
Writing File : fprintf() function
The fprintf() function is used to write set of characters into file. It sends formatted
output to a stream.
Syntax:
int fprintf(FILE *stream, const char *format [, argument, ...])](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-109-320.jpg)
![C PROGRAMMING
109
Example:
1. #include <stdio.h>
2. main(){
3. FILE *fp;
4. fp = fopen("file.txt", "w");//opening file
5. fprintf(fp, "Hello file by fprintf...n");//writing data into file
6. fclose(fp);//closing file
7. }
Reading File : fscanf() function
The fscanf() function is used to read set of characters from file. It reads a word from
the file and returns EOF at the end of file.
Syntax:
int fscanf(FILE *stream, const char *format [, argument, ...])
Example:
1. #include <stdio.h>
2. main(){
3. FILE *fp;
4. char buff[255];//creating char array to store data of file
5. fp = fopen("file.txt", "r");
6. while(fscanf(fp, "%s", buff)!=EOF){
7. printf("%s ", buff );
8. }
9. fclose(fp);
10. }
Output:
Hello file by fprintf...](https://image.slidesharecdn.com/cprogramming-230807194036-e941981a/85/C-programming-pdf-110-320.jpg)
C programming.pdf
- 1. C PROGRAMMING DINESHKUMAR THANGAVEL PARUL UNIVERSITY
- 2. C PROGRAMMING 1 What is C language? Different ways of defining C: 1)C as a mother language C language is considered as the mother language of all the modern programming languages because most of the compilers, JVMs, Kernels, etc. are written in C language, and most of the programming languages follow C syntax, for example, C++, Java, C#, etc. It provides the core concepts like the array strings functions filehandling thatarebeingusedinmanylanguageslikeC++ Java C# etc. 2) C as a system programming language A system programming language is used to create system software. C language is a system programming language because it can be used to do low-level programming (for example driver and kernel). It is generally used to create hardware devices, OS, drivers, kernels, etc. For example, Linux kernel is written in C. It can't be used for internet programming like Java, .Net, PHP, etc. 3) C as a procedural language A procedure is known as a function, method, routine, subroutine, etc. A procedural language specifies a series of steps for the program to solve the problem. A procedural language breaks the program into functions, data structures, etc. C is a procedural language. In C, variables and function prototypes must be declared before being used.
- 3. C PROGRAMMING 2 4) C as a structured programming language A structured programming language is a subset of the procedural language. Structure means to break a program into parts or blocks so that it may be easy to understand. 5) C as a mid-level programming language C is considered as a middle-level language because it supports the feature of both low-level and high-level languages. C language program is converted into assembly code, it supports pointer arithmetic (low-level), but it is machine independent (a feature ofhigh-level). A Low-level language is specific to one machine, i.e., machine dependent. It is machine dependent, fast to run. But it is not easy to understand. A High-Level language is not specific to one machine, i.e., machine independent. It is easy to understand. History of C: Brief History of C Programming Language: C is developed by Dennis Ritchie in the year 1972 at Bell Laboratories(USA). It is a General- purpose, Structured, Machine Independent, Simple and Flexible programming language. It was mainly developed as a system programming language to write an operating system. Features of C Programming Language High-Level Language C provides strong abstraction in case of its libraries and built-in features that make it machine- independent. It is capable enough to develop system applications such as the kernel, driver, etc. Structured Language
- 4. C PROGRAMMING 3 C Language supports structured programming which includes the use of functions. Functions reduce the code complexity and are totally reusable. Rich Library: Unlike its predecessors, C language incorporates multiple built- in arithmetic and logical functions along with many built-in libraries which make development faster and convenient. Extensible: C Language is a High-level language and is also open for upgrades. Hence, the programming language is considered to be extensible like any other high-level languages. Recursion C Language supports function back-tracking which involves recursion. In the process of recursion, a function is called within another function for multiple numbers of times. Pointers C enables users to directly interact with memory using the pointers. We use pointers in memory, structure, functions, arrays, stack and many more. Faster: C Language comes with a minimal number of libraries and built-in functions which makes the compile and execution-times to be less and the system faces low overhead. Memory Management: C provides the best in class memory management. It can both allocate and deallocate memory dynamically. the malloc(), calloc(), realloc() functions are used to allocate memory dynamically and free() function is used to deallocate the used memory at any instance of time. Structure of C programming:
- 6. C PROGRAMMING 5 Pre-processor directives in C: The pre-processor will process directives that are inserted into the C source code. These directives allow additional actions to be taken on the C source code before it is compiled into object code. Directives are not part of the C language itself.
- 7. C PROGRAMMING 6 Tokens in C Tokens in C is the most important element to be used in creating a program in C. We can define the token as the smallest individual element in C. For `example, we cannot create a sentence without using words; similarly, we cannot create a program in C without using tokens in C. Therefore, we can say that tokens in C is the building block or the basic component for creating a program in C language. Classification of tokens in C Tokens in C language can be divided into the following categories: o Keywords inC o Identifiers in C o Strings in C o Operators in C o Constant in C o Special Characters in C Keywords in C A keyword is a reserved word. You cannot use it as a variable name, constant name, etc. There are only 32 reserved words (keywords) in the C language.
- 8. C PROGRAMMING 7 A list of 32 keywords in the c language is given below: auto break case char const continue default do double else enum extern float for goto if int long register return short signed sizeof static struct switch typedef union unsigned void volatile while C Identifiers C identifiers represent the name in the C program, for example, variables, functions, arrays, structures, unions, labels, etc. An identifier can be composed of letters such as uppercase, lowercase letters, underscore, digits, but the starting letter should be either an alphabet or an underscore. If the identifier is not used in the external linkage, then it is called as an internal identifier. If the identifier is used in the external linkage, then it is called as an external identifier. Rules for constructing C identifiers o The first character of an identifier should be either an alphabet or an underscore, and then it can be followed by any of the character, digit, or underscore. o It should not begin with any numerical digit. o In identifiers, both uppercase and lowercase letters are distinct. Therefore, we can say that identifiers are case sensitive. o Commas or blank spaces cannot be specified within an identifier. o Keywords cannot be represented as anidentifier. o The length of the identifiers should not be more than 31 characters. o Identifiers should be written in such a way that it is meaningful, short, and easy to read. Example of valid identifiers: total, sum, average, a12, a_12, ab, place, college etc..
- 9. C PROGRAMMING 8 Types of identifiers o Internal identifier o External identifier Internal Identifier If the identifier is not used in the external linkage, then it is known as an internal identifier. The internal identifiers can be local variables. External Identifier If the identifier is used in the external linkage, then it is known as an external identifier. The external identifiers can be function names, global variables. Differences between Keyword and Identifier Keyword Identifier Keyword is apre-defined word. The identifier is a user-defined word It must be written in a lowercase letter. It can be written in both lowercase and uppercase letters. Its meaning is pre-defined in the c compiler. It is a combination of alphabetical characters. It does not contain the underscore character. Its meaning is not defined in the c compiler. It is a combination of alphanumeric characters. It can contain the underscore character. Let's understand through an example. 1. int main() 2. { 3. int a=10; 4. int A=20; 5. printf("Value of a is : %d",a); 6. printf("nValue of A is :%d",A); 7. return 0; 8. }
- 10. C PROGRAMMING 9 C Operators An operator is simply a symbol that is used to perform operations. There can be many types of operations like arithmetic, logical, bitwise, etc. There are following types of operators to perform different types of operations in C language. o Arithmetic Operators o Relational Operators o Shift Operators o Logical Operators o Bitwise Operators o Ternary or Conditional Operators o Assignment Operator o Misc Operator Arithmetic Operators The following table shows all the arithmetic operators supported by the C language. Assume variable A holds 10 and variable B holds 20 then − Show Examples Operator Description Example + Adds two operands. A + B = 30 − Subtracts second operand from the first. A − B = -10 * Multiplies both operands. A * B = 200 / Divides numerator by de-numerator. B / A = 2
- 11. C PROGRAMMING 10 % Modulus Operator and remainder of after an integer division. B % A = 0 ++ Increment operator increases the integer value by one. A++ = 11 -- Decrement operator decreases the integer value by one. A-- = 9 Relational Operators The following table shows all the relational operators supported by C. Assume variable A holds 10 and variable B holds 20 then − Show Examples Operator Description Example == Checks if the values of two operands are equal or not. If yes, then the condition becomes true. (A == B) is not true. != Checks if the values of two operands are equal or not. If the values are not equal, then the condition becomes true. (A != B) is true. > Checks if the value of left operand is greater than the value of right operand. If yes, then the condition becomes true. (A > B) is not true. < Checks if the value of left operand is less than the value of right operand. If yes, then the condition becomes true. (A < B) is true. >= Checks if the value of left operand is greater than or equal to the value of right operand. If yes, then the condition becomes true. (A >= B) is not true. <= Checks if the value of left operand is less than or equal to the value of right operand. If yes, then the condition becomes true. (A <= B) is true.
- 12. C PROGRAMMING 11 Logical Operators Following table shows all the logical operators supported by C language. Assume variable A holds 1 and variable B holds 0, then − Show Examples Operator Description Example && Called Logical AND operator. If both the operands are non-zero, then the condition becomes true. (A && B) is false. || Called Logical OR Operator. If any of the two operands is non-zero, then the condition becomes true. (A || B) is true. ! Called Logical NOT Operator. It is used to reverse the logical state of its operand. If a condition is true, then Logical NOT operator will make it false. !(A && B) is true. Bitwise Operators Bitwise operator works on bits and perform bit-by-bit operation. The truth tables for &, |, and ^ is as follows − p q p & q p | q p ^ q 0 0 0 0 0 0 1 0 1 1 1 1 1 1 0 1 0 0 1 1 Assume A = 60 and B = 13 in binary format, they will be as follows − A = 0011 1100 B = 0000 1101 A&B = 0000 1100
- 13. C PROGRAMMING 12 A|B = 0011 1101 A^B = 0011 0001 ~A = 1100 0011 The following table lists the bitwise operators supported by C. Assume variable 'A' holds 60 and variable 'B' holds 13, then − Show Examples Operator Description Example & Binary AND Operator copies a bit to the result if it exists in (A & B) both operands. = 12, i.e., 0000 1100 | Binary OR Operator copies a bit if it exists in either (A | B) = operand. 61, i.e., 0011 1101 ^ Binary XOR Operator copies the bit if it is set in one (A ^ B) = operand but not both. 49, i.e., 0011 0001 ~ (~A ) = Binary One's Complement Operator is unary and has the ~(60), effect of 'flipping' bits. i.e,. - 0111101 << Binary Left Shift Operator. The left operands value is A << 2 = moved left by the number of bits specified by the right 240 i.e., operand. 1111 0000
- 14. C PROGRAMMING 13 >> Binary Right Shift Operator. The left operands value is A >> 2 = moved right by the number of bits specified by the right 15 i.e., operand. 0000 1111 Assignment Operators The following table lists the assignment operators supported by the C language − Show Examples Operator Description Example = Simple assignment operator. Assigns values from right side operands to C = A + B left side operand will assign the value of A + B to C += Add AND assignment operator. It adds the right operand to the left C += A is operand and assign the result to the left operand. equivalent to C = C + A -= Subtract AND assignment operator. It subtracts the right operand from C -= A is the left operand and assigns the result to the left operand. equivalent to C = C - A *= Multiply AND assignment operator. It multiplies the right operand with the C *= A is left operand and assigns the result to the left operand. equivalent to C = C * A /= Divide AND assignment operator. It divides the left operand with the right C /= A is operand and assigns the result to the left operand. equivalent to C = C / A
- 15. C PROGRAMMING 14 %= Modulus AND assignment operator. It takes modulus using two operands and assigns the result to the left operand. C %= A is equivalent to C = C % A <<= Left shift AND assignment operator. C <<= 2 is same as C = C << 2 >>= Right shift AND assignment operator. C >>= 2 is same as C = C >> 2 &= Bitwise AND assignment operator. C &= 2 is same as C = C & 2 ^= Bitwise exclusive OR and assignment operator. C ^= 2 is same as C = C ^ 2 |= Bitwise inclusive OR and assignment operator. C |= 2 is same as C = C | 2 Misc Operators ↦ sizeof & ternary Besides the operators discussed above, there are a few other important operators including sizeof and ? : supported by the C Language. Show Examples Operator Description Example sizeof() Returns the size of a variable. sizeof(a), where a is integer, will return 4. & Returns the address of a variable. &a; returns the actual address of the variable.
- 16. C PROGRAMMING 15 * Pointer to a variable. *a; ? : Conditional Expression. If Condition is true ? then value X : otherwise value Y Operators Precedence in C Operator precedence determines the grouping of terms in an expression and decides how an expression is evaluated. Certain operators have higher precedence than others; for example, the multiplication operator has a higher precedence than the addition operator. For example, x = 7 + 3 * 2; here, x is assigned 13, not 20 because operator * has a higher precedence than +, so it first gets multiplied with 3*2 and then adds into 7. Here, operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom. Within an expression, higher precedence operators will be evaluated first. Show Examples Category Operator Associativity Postfix () [] -> . ++ - - Left to right Unary + - ! ~ ++ - - (type)* & sizeof Right to left Multiplicative * / % Left to right Additive + - Left to right Shift << >> Left to right Relational < <= > >= Left to right Equality == != Left to right Bitwise AND & Left to right Bitwise XOR ^ Left to right
- 17. C PROGRAMMING 16 Bitwise OR | Left to right Logical AND && Left to right Logical OR || Left to right Conditional ?: Right to left Assignment = += -= *= /= %=>>= <<= &= ^= |= Right to left Comma , Left to right Example: // Working of arithmetic operators #include <stdio.h> int main() { int a = 9,b = 4, c; c = a+b; printf("a+b = %d n",c); c = a-b; printf("a-b = %d n",c); c = a*b; printf("a*b = %d n",c); c = a/b; printf("a/b = %d n",c); c = a%b; printf("Remainder when a divided by b = %d n",c); return 0; }
- 18. C PROGRAMMING Precedence of Operators in C The precedence of operator species that which operator will be evaluated first and next. The associativity specifies the operator direction to be evaluated; it may be left to right or right to left. Let's understand the precedence by the example given below: 1. int value=10+20*10; The value variable will contain 210 because * (multiplicative operator) is evaluated before + (additive operator). The precedence and associativity of C operators is given below: Category Operator Associativity Postfix () [] -> . ++ - - Left to right Unary + - ! ~ ++ - - (type)* & sizeof Right to left Multiplicative * / % Left to right Additive + - Left to right Shift << >> Left to right Relational < <= > >= Left to right Equality == != Left to right Bitwise AND & Left to right Bitwise XOR ^ Left to right Bitwise OR | Left to right Logical AND && Left to right Logical OR || Left to right Conditional ?: Right to left Assignment = += -= *= /= %=>>= <<= &= ^= |= Right to left Comma , Left to right 17
- 19. C PROGRAMMING 18 ASCII value in C What is ASCII code? The full form of ASCII is the American Standard Code for information interchange. It is a character encoding scheme used for electronics communication. Each character or a special character is represented by some ASCII code, and each ascii code occupies 7 bits in memory. In C programming language, a character variable does not contain a character value itself rather the ascii value of the character variable. The ascii value represents the character variable in numbers, and each character variable is assigned with some number range from 0 to 127. For example, the ascii value of 'A' is 65. In the above example, we assign 'A' to the character variable whose ascii value is 65, so 65 will be stored in the character variable rather than 'A'. We will create a program which will display the ascii value of the character variable. 1. #include <stdio.h> 2. int main()
- 20. C PROGRAMMING 19 3. { 4. char ch; // variable declaration 5. printf("Enter a character"); 6. scanf("%c",&ch); // user input 7. printf("n The ascii value of the ch variable is : %d", ch); 8. return 0; 9. } Escape Sequence in C An escape sequence in C language is a sequence of characters that doesn't represent itself when used inside string literal or character. It is composed of two or more characters starting with backslash . For example: n represents new line. List of Escape Sequences in C Escape Sequence Meaning a Alarm or Beep b Backspace f Form Feed n New Line r Carriage Return t Tab (Horizontal) v Vertical Tab Backslash ' Single Quote
- 21. C PROGRAMMING 20 " Double Quote ? Question Mark nnn octal number xhh hexadecimal number 0 Null Example: #include<stdio.h> int main(){ int number=50; printf("Younarenlearningn'c' languagen"Do you know C language""); return 0; } C Format Specifier The Format specifier is a string used in the formatted input and output functions. The format string determines the format of the input and output. The format string always starts with a '%' character. The commonly used format specifiers in printf() function are: Format specifier Description %d or %i It is used to print the signed integer value where signed integer means that the variable can hold both positive and negative values. %u It is used to print the unsigned integer value where the unsigned integer means that the variable can hold only positive value. %o It is used to print the octal unsigned integer where octal integer value always starts with a 0 value.
- 22. C PROGRAMMING 21 %x It is used to print the hexadecimal unsigned integer where the hexadecimal integer value always starts with a 0x value. In this, alphabetical characters are printed in small letters such as a, b, c, etc. %X It is used to print the hexadecimal unsigned integer, but %X prints the alphabetical characters in uppercase such as A, B, C, etc. %f It is used for printing the decimal floating-point values. By default, it prints the 6 values after '.'. %e/%E It is used for scientific notation. It is also known as Mantissa or Exponent. %g It is used to print the decimal floating-point values, and it uses the fixed precision, i.e., the value after the decimal in input would be exactly the same as the value in the output. %p It is used to print the address in a hexadecimal form. %c It is used to print the unsigned character. %s It is used to print the strings. %ld It is used to print the long-signed integer value. Type Casting in C Typecasting allows us to convert one data type into other. In C language, we use cast operator for typecasting which is denoted by (type). Syntax: 1. (type)value; Note: It is always recommended to convert the lower value to higher for avoiding data loss. Without Type Casting: 1. int f= 9/4; 2. printf("f : %dn", f );//Output: 2
- 23. C PROGRAMMING 22 Static in C Static is a keyword used in C programming language. It can be used with both variables and functions, i.e., we can declare a static variable and static function as well. An ordinary variable is limited to the scope in which it is defined, while the scope of the static variable is throughout the program. Static keyword can be used in the following situations: o Staticglobalvariable When a global variable is declared with a static keyword, then it is known as a static global variable. It is declared at the top of the program, and its visibility is throughout the program. o Static function When a function is declared with a static keyword known as a static function. Its lifetime is throughout the program. o Static local variable When a local variable is declared with a static keyword, then it is known as a static local variable. The memory of a static local variable is valid throughout the program, but the scope of visibility of a variable is the same as the automatic local variables. However, when the function modifies the static local variable during the first function call, then this modified value will be available for the next function callalso. Datatypes and Variables Datatypes in C are broadly classified into four categories as follows.
- 24. C PROGRAMMING 23 Basic Datatypes Basic Datatypes are considered as the most fundamental and primary datatypes that C has to offer. The Datatypes that come under Basic Datatypes are as follows. Datatype Name Datatype Size Datatype Range short 1 byte -128 to 127 unsigned short 1 byte 0 to 255 char 1 byte -128 to 127 unsigned char 1 byte 0 to 255 int 2 bytes -32,768 to 32,767 unsigned int 2 bytes 0 to 65,535 long unsigned long 4 bytes 4 bytes -2,147,483,648 to 2,147,483,647 0 to 4,294,967,295 float 4 bytes 3.4E-38 to 3.4E+38
- 25. C PROGRAMMING 24 double 8 bytes 1.7E-308 to 1.7E+308 long double 10 bytes 3.4E-4932 to 1.1E+4932 Derived Datatypes A derived type is formed by using one or more basic types in combination. They are the object types whose functionalities are predefined in the C libraries. Function types Pointer types Array types Structure types Union types Enumeration Datatypes Enumerated Datatypes are used to declare Integral constants in C programming language so that the integral constant names are easy to remember and maintain. The keyword enum is used to declare enumerated datatypes. example: enum plug{on = 1, off = 0}; Void Datatypes The void data type is an empty data type that is used as a return type for the functions that return no value in C. example: void function(int n) int function(void) Variables in C Variable is defined as the reserved memory space which stores a value of a definite datatype. The value of the Variable is not constant, instead, it allows changes. There are mainly five types of variables supported in C. local variable global variable static variable automatic variable external variable
- 26. C PROGRAMMING 25 Local Variables Any variable that is declared at the inside a code block or a function and has the scope confined to that particular block of code or function is called to be a local variable. //Example 1Void Edu() 2{ 3 int Local_variable=10; 4} Global Variables Any variable that is declared at the outside a code block or a function and has the scope across the entire program and allows any function to change it’s value is known as Global Variable. //Example 1int Global_variable=10; 2void Edu() 3{ 4 int Local_variable=20; 5} Static Variables Any variable that is declared using the keyword static is known as a Static Variable. Static Variables retain the declared value throughout the entire execution of the program and will not be changed between multiple function calls. //Example void Edu() { int Local_variable =10;// static int Static_variable =10; Local_variable=Local_variable+1; Static_variable =Static_variable+1; printf("%d,%d",x,y); }
- 27. C PROGRAMMING 26 Automatic Variables Automatic Variables can be declared by using the keyword auto. By default, all the variables declared in C language are Automatic Variables. //Example void main() { int Local_variable=10; //(automatic default) auto int auto=20; //(automatic variable) }; External Variables External Variables are declared by using the extern keyword. We can share a variable in multiple C source files by using an external variable. //Example extern external=10; 1 Formatted input and output : printf() and scanf() in C The printf() and scanf() functions are used for input and output in C language. Both functions are inbuilt library functions, defined in stdio.h (header file). printf() function The printf() function is used for output. It prints the given statement to the console. The syntax of printf() function is given below: printf("format string",argument_list); The format string can be %d (integer), %c (character), %s (string), %f (float) etc. scanf() function The scanf() function is used for input. It reads the input data from the console. scanf("format string",argument_list);
- 28. C PROGRAMMING 27 enter a number:5 cube of number is:125 Program to print cube of given number Let's see a simple example of c language that gets input from the user and prints the cube of the given number. #include<stdio.h> int main(){ int number; printf("enter a number:"); scanf("%d",&number); printf("cube of number is:%d ",number*number*number); return 0; } Output The scanf("%d",&number) statement reads integer number from the console and stores the given value in number variable. The printf("cube of number is:%d ",number*number*number) statement prints the cube of number on the console Let us execute our first C Program. First C Program In this C Programming Tutorial, we will understand the basic structure of a C Program. Any basic C program consists of the following sections
- 29. C PROGRAMMING 28 Preprocessor Directives Preprocessor Directives are declared at the beginning of every C Program with a special character #. They are defined as predefined functions or Macro programs that are invoked and compiled by the C Compiler during the compilation process. Functions Functions in C Program are defined as the subdivided program of the main program. Functions provide code reusability and decrease code complexity. Variables Variable is defined as a name declared to a store the values in a C Program. Every variable used in C has a specific data type that determines the size and layout of the variable’s memory. Statements & Expressions:Statements are nothing but the instructions we provideto the computer to compile and the expressions, on the other hand, are considered to be the mathematical or the logical statements which yield into a resultant value. Comments Comments are the messages written by the developer in the code for easy understanding of the logic of the code used while programming. The comments will not be compiled by the compiler. the comments are written within // or /* */. Let us now execute our first Hello World Program. 1#include<stdio.h> 2//main fn 3int main(){ 4/* printing hello world*/
- 30. C PROGRAMMING 29 5 printf("Hello World"); return 0; } //Output Hello World Conditional/ Decision making Statements in C Programming: Conditional Statements in C language can be defined as the programming statements that are designed to decide the execution flow of the statements of the program over the specified mathematical or logical condition. The important conditional statements in this C Programming tutorial are as follows. if If Statement in C language is a programming conditional statement that executes a code segment over a condition, provided if it is true and valid. Below is the flowchart for if condition. //Example 1#include<stdio.h> 2int main() 3{ 4 int number=0; 5 printf("Enter a number:"); 6 scanf("%d",&number); 7 if(number%2==0){ 8 printf("your number is %d and it is an 9even number",number); 10 } 11 return 0;
- 31. C PROGRAMMING 30 //Output Enter a number:4 your number is 4 and it is an even number else-if Else If Conditional Statement in C language is used to execute one statement out of the two. The Conditional Statement executes the code segment provided is true and valid. Below is the flowchart for the else-if condition. //Example #include<stdio.h> int main() 1{ 2 int number=0; 3 printf("enter a number:"); 4 scanf("%d",&number); 5 if(number%2==0) 6 { 7 printf("your number is %d and it is an even 8number",number); 9 } 10 else 11 { 12 printf("your number is %d and it is an odd 13number",number); 14 15 16} } return 0; }
- 32. C PROGRAMMING 31 //Output Enter a number:5 your number is 5 and it is an odd number else-if ladder Else if Ladder in C language is set of consecutive Else-If statements which are used to execute one true and valid statement out of a collection of given statements. Below is the flowchart for the else-if ladder condition. 1#include<stdio.h> 2int main() 3{ 4 int number=0; 5 printf("enter a number:"); 6 scanf("%d",&number); 7 if(number==10) 8 { 9 printf("your inputted number is equals to 10"); 10 }
- 33. C PROGRAMMING 32 11 12 { 13 14 } else if(number==50) printf("your inputted number is equal to 50"); 15 16 17 18 19 20 { 21 22 } else if(number==100) { printf("your inputted number is equal to 100"); } else printf("your inputted number is not equal to 10, 50 or 100"); 23 24} return 0; //Output enter a number:5 your inputted number is not equal to 10, 50 or 100 Nested if Nested-If in C language is a conditional statement where one Else-If statement is embedded into another If statement. Below is the flowchart for the nested-if condition. //Example 1#include<stdio.h> 2int main() 3{ 4 int v1, v2; 5 printf("Enter the value of First variable :"); 6 scanf("%d",&v1); 7 printf("Enter the value of Second variable :");
- 34. C PROGRAMMING 33 8 scanf("%d",&v2); 9 if (v1 != v2) 10 { 11 printf("First variable is not equal to Second variablen"); 12 13 14 15variablen"); 16 17 18 19 20variablen"); 21 if (v1<v2) { printf("First variable is not equal to Second } else { printf("Second variable is greater than First } 22 } 23 else 24 { 25 26 } printf("First variable is equal to Second variablen"); } //Output: return 0; Enter the value of First variable :12 Enter the value of Second variable :21 First variable is not equal to Second variable Second variable is greater than First variable Looping Statements: Loops in C are defined as a programming statement that is designed to execute a particular code segment for a specific number of times or until a particular condition provided is satisfied. There are mainly three-loop statements available in C. How it Works: The below diagram depicts a loop execution,
- 35. C PROGRAMMING 34 As per the above diagram, if the Test Condition is true, then the loop is executed, and if it is false then the execution breaks out of the loop. After the loop is successfully executed the execution again starts from the Loop entry and again checks for the Test condition, and this keeps on repeating. The sequence of statements to be executed is kept inside the curly braces { } known as the Loop body. After every execution of the loop body, condition is verified, and if it is found to be true the loop body is executed again. When the condition check returns false, the loop body is not executed, and execution breaks out of the loop. Types of Loop There are 3 types of Loop in C language, namely: 1. while loop 2. for loop 3. do while loop
- 36. C PROGRAMMING 35 variable initialization; while(condition) { statements; variable increment or decrement; } #include<stdio.h> while loop while loop can be addressed as an entry control loop. It is completed in 3 steps. Variable initialization.(e.g int x =0;) condition(e.g while(x <=10)) Variable increment or decrement ( x++ or x-- or x = x + 2) Syntax : Example: Program to print first 10 natural numbers
- 37. C PROGRAMMING 36 void main( ) { int x; x = 1; while(x <= 10) { printf("%dt", x); /* below statement means, do x = x+1, increment x by 1*/ x++; } } 1 2 3 4 5 6 7 8 9 10 do while loop In some situations it is necessary to execute body of the loop before testing the condition. Such situations can be handled with the help of do- while loop. do statement evaluates the body of the loop first and at the end, the condition is checked using while statement. It means that the body of the loop will be executed at least once, even though the starting condition inside while is initialized to be false. General syntax is,
- 38. C PROGRAMMING 37 #include<stdio.h> void main() { int a, i; a = 5; i = 1; do example: Program to print first 10 multiples of 5. do { ..... ..... } while(condition)
- 39. C PROGRAMMING 38 while loop vs do-while loop in C Let's see some Comparison between the while loop and do-while loop in the C language SR.NO whileloop do-while loop 1. While the loop is an entry control loop because firstly, the condition is checked, then the loop's body is executed. The do-while loop is an exit control loop because in this, first of all, the body of the loop is executed then the condition is checked true or false. 2. The statement of while loop may not be executed at all. The statement of the do-while loop must be executed at least once. 3. The while loop terminates when the condition becomes false. As long as the condition is true, the compiler keeps executing the loop in the do-while loop. 4. In a while loop, the test condition variable must be initialized first to check the test condition in the loop. In a do-while loop, the variable of test condition Initialized in the loop also. 5. In a while loop, at the end of the condition, there is no semicolon. Syntax: while (condition) In this, at the end of the condition, there is a semicolon. Syntax: while (condition); { printf("%dt", a*i); i++; } while(i <= 10); }
- 40. C PROGRAMMING 39 6. While loop is not used for creating menu-driven programs. It is mostly used for creating menu- driven programs because at least one time; the loop is executed whether the condition is true or false. 7. In a while loop, the number of In a do-while loop, irrespective of the executions depends on the condition condition mentioned, a minimum of 1 defined in the while block. execution occurs. 8. Syntax of while loop: Syntax of do-while loop: while (condition) { Block of statements; } Statement-x; do { statements; } while (condition); Statement-x; 9. Program of while loop: Program of do-while loop: Program of while loop: #include #include #include Void main() #include Void main() { int i; clrscr(); i = 1; while(i<=10) { printf("hello"); i = i + 1; } getch(); } { int i; clrscr(); i = 1; do { printf("hello"); i = i + 1; } while(i<=10); getch(); }
- 41. C PROGRAMMING 40 for(initialization; condition; increment/decrement) { statement-block; } 10. Flowchart of while loop: Flowchart of do-while loop: for loop for loop is used to execute a set of statements repeatedly until a particular condition is satisfied. We can say it is an open ended loop.. General format is, In for loop we have exactly two semicolons, one after initialization and second after the condition. In this loop we can have more than one initialization or increment/decrement, separated using comma operator. But it can have only one condition.
- 42. C PROGRAMMING 41 #include<stdio.h> void main( ) { int x; The for loop is executed as follows: 1. It first evaluates the initialization code. 2. Then it checks the condition expression. 3. If it is true, it executes the for-loop body. 4. Then it evaluate the increment/decrement condition and again follows from step 2. 5. When the condition expression becomes false, it exits the loop. Example: Program to print first 10 natural numbers
- 43. C PROGRAMMING 42 for(initialization; condition; increment/decrement) { for(initialization; condition; increment/decrement) { statement ; } } #include<stdio.h> Nested for loop We can also have nested for loops, i.e one for loop inside another for loop. Basic syntax is, Example: Program to print half Pyramid of numbers 1 2 3 4 5 6 7 8 9 10 } for(x = 1; x <= 10; x++) { printf("%dt", x); }
- 44. C PROGRAMMING 43 1 21 321 4321 54321 void main( ) { int i, j; /* first for loop */ for(i = 1; i < 5; i++) { printf("n"); /* second for loop inside the first */ for(j = i; j > 0; j--) { printf("%d", j); } } } Copy
- 45. C PROGRAMMING 44 Jumping Out of Loops Sometimes, while executing a loop, it becomes necessary to skip a part of the loop or to leave the loop as soon as certain condition becomes true. This is known as jumping out of loop. 1) break statement When break statement is encountered inside a loop, the loop is immediately exited and the program continues with the statement immediately following the loop. 2) continue statement It causes the control to go directly to the test-condition and then continue the loop process. On encountering continue, cursor leave the current cycle of loop, and starts with the next cycle.
- 46. C PROGRAMMING 45 Example: #include<stdio.h> int main() { int i; for(i = 0; i < 10; i++) { if( i % 4 == 0 ) { /* when i is divisible by 4 continue to the next iteration */ continue; } printf("%dn", i); } // signal to operating system everything works fine return 0; }
- 47. C PROGRAMMING 46
- 48. C PROGRAMMING 47 Data Structures in C Programming A Data structure can be defined as a collection of data values, the relationships among them, and the functions that are applied on to the data. They are broadly classified as follows. Primitive Data Structures / Built-in Data Structures Abstract Data Structures / User-Defined Data Structures Arrays An array is defined as the collection of similar type of data items stored at contiguous memory locations. The array is the simplest data structure where each data element can be randomly accessed by using its index number. There are three different types of Arrays, namely: One-Dimensional Array Two-Dimensional Array Multi-Dimensional Array One-Dimensional Array The One-dimensional array can be defined as an array with a single row and multiple columns. The elements in the 1D array are accessed using their index numbers.
- 49. C PROGRAMMING 48 1int arrayone[10]; Two-Dimensional Array The two-dimensional array can be defined as an array of arrays. The 2D array is organized as matrices which can be represented as the collection of rows and columns. The elements of the array are accessed using their intersection coordinates. int arraytwo[10][5]; 1 Multi-Dimensional Array The multi-dimensional array can be defined as an array of arrays. The 3D array is organized as 3D matrix which can be represented as the collection of multiple rows and columns. The elements of the array are accessed using their 3D intersection coordinates. 1int arraythree[10][10][10]; Why do we need it? In this article, you will learn about the data structure array and its types and why is it a widely used data structure. Let’s get into it. An Array is a sequential collection of elements, of the same data type. They are stored sequentially in memory. An Array is a data structure that holds a similar type of elements. The array elements are not treated as objects in c like they are in java. Imagine you are at a musical instrument store and I tell you to arrange all the keyboards under the brand Casio at one place one above the other. This sequential collection of records is called
- 50. C PROGRAMMING 49 an Array. An array is a sequential collection of elements of the same data type. In our example above, Casio is the data type and all the keyboards you collected are of the brand Casio. All the elements in an array are addressed by a common name. There are two types of arrays: 1. Single dimensional array 2. Array Initialization 3. Accessing Array at any Point 4. Multidimensional array SINGLE DIMENSIONAL ARRAY The syntax for declaring a Single Dimensional Array: Datatype arrayName[arraySize]; We have a data type that can be any of the basic data types like int, float or double. Array Name is the name of the array and we declare the size of the array. In our above example, the array will be, Casio keyboardArray[100]; Let’s consider another example: int test[30]; The array test will hold the elements of type int and will have a size 30. ARRAY SIZE: Array size is given at the time of declaration of the array. Once the size of the array is given it cannot be changed. The compiler then allocates that much memory space to the array. Consider the Example: int test[20];
- 51. C PROGRAMMING 50 In the example above, we have an array test, of type int. We have given the array size to be 20. This means that 20 consecutive memory locations will be left free for the array in the memory. ARRAY INDEX AND INITIALIZATION A number associated with each position in an array and this number is called the array index. Its starts from 0 and to the last element, that is the size of the array minus one. The minus one is there because we start counting from zero and not one. Array indices always begin fromzero. Consider this example, this is the age array. Here the array contains the values 12,41,3,13,7 and the indices are 0,1,2,3,4. If we want to represent an element at index 4 it is represented as age[4] and the value 7 will be displayed. By default, the array contains all zero values. Array initialization is done at the time of declaration. This can also be carried out later if the user enters the array value as and when needed. INITIALIZATION DURING DECLARATION: An array can be initialized during declaration. This is done by specifying the array elements at the time of declaration. Here the array size is also fixed and it is decided by us. Consider the code, #include<stdio.h> int main() { int arr[] = { 10, 20, 30, 40 } ; return 0; } EXPLANATION:
- 52. C PROGRAMMING 51 In the above example, we create an array of type int and with the name arr. We directly specify the array elements. The size of the array is decided by counting the number of elements in our array. In this case, the size is 4. INITIALIZATION BY USER: In this method, we let the user decide the size of the array. In this case, we need a variable to hold the size of the array and a for loop to accept the elements of the array. We assign a random size at the time of declaration and use only as needed. The size at the start is usually at the higher side. We have a variable i to control the for loop. Consider the example, #include<stdio.h> int main() { int arr[50],n,i ; printf("Enter the size of array:n"); scanf(“%d ”,n); printf("Enter the elements of array:n"); for(i=0;i<n;i++) { Scanf(“%d ”,arr[i]); } return 0; } OUTPUT: EXPLANATION:
- 53. C PROGRAMMING 52 In the above program, we declare an array of size 50. We then ask the user to enter the number of elements he wishes to enter in this array. We then accept the array elements entered by the user.
- 54. C PROGRAMMING 53 DISPLAYING THE ARRAY: Displaying the array also requires the for-loop. We traverse to the entire array and display the elements of the array. Here is an example, #include<stdio.h> int main() { int arr[50],n,i ; printf("Enter the size of array:n"); scanf(“%d ”,n); printf("Enter the elements of array:n"); for(i=0;i<n;i++) { Scanf(“%d ”,arr[i]); } printf("Array Elements are:n"); for(i=0;i<n;i++) { Printf(“%d ”,arr[i]); } return 0; } OUTPUT:
- 55. C PROGRAMMING 54 EXPLANATION: In the above program, we declare an array of size 50. We then ask the user to enter the number of elements he wishes to enter in this array. We then accept the array elements entered by the user. We then use a for loop again to display the array elements. ACCESSING THE ARRAY AT ANY POINT: Accessing array elements is simple and is done by using the array index. Have a look at the code below. #include<stdio.h> int main() { int arr[5],i ; arr[4]=2; arr[2]=17; arr[0]=17; printf("Array elements are: n"); for(i=0;i<5;i++) { printf(“%d ”,arr[i]); } return 0;
- 56. C PROGRAMMING 55 } OUTPUT: EXPLANATION: In the program above, we have an array of size 5. We enter elements at different locations using array index. We print the array to get the above output. By Default, all the array elements are zero. What happens if we cross the array size? In c, if we try to access the elements out of bound, error may not be shown by the compiler but we will not get proper output. MULTI-DIMENSIONAL ARRAY: Arrays of arrays are multi-dimensional arrays. This is because each element in a multi- dimensional array has an array of its own. We need n for loops to iterate through a multidimensional array depending on the dimensions. SYNTAX FOR DECLARING MULTI_DIMENSIONAL ARRAYS: Datatype arrayname[size1][size2]…..[size n]; Consider the example, int a[10][20]; The size of the above array will be 10*20 that is 200 elements. Similarly, we can have two or three or even more dimensional arrays. Each dimension requires one for loop. So, the two-dimensional array requires two- and three- dimensional array requires three. Consider the code: #include<stdio.h> int main() {
- 57. C PROGRAMMING 56 int arr[3][2] = {{0,1}, {2,3}, {4,5}}; for (int i = 0; i < 3; i++) { for (int j = 0; j < 2; j++) { printf( "Element: %d n”,arr[i][j]); } } return 0; } EXPLANATION: In the above code, we display a 3*2 matrix. This array has 3 rows and 2 columns. We have 2 for loops. Each responsible for one dimension of the array. The outer for loop takes care of rows and inner of columns. Similarly, we can write a code for three-dimensional array and there will be three for loops and each dimension will be controlled by one for loop.
- 58. C PROGRAMMING 57 Strings The string is defined as a one-dimensional array of characters terminated by a null character. The character array or the string is used to store text such as word or sentences. Each character in the array occupies one byte of memory, and the last character must always be0. Two types of strings are: char array string literal The String functions available in C language are as follows Function Functionality strlen() Returns the length of the String strcpy() Copies String from Source to Destination strcat() Joins two Strings and stores result in first strcmp() Compares the given two Strings strrev() Reverses the String strlwr() Converts String to Lower case strupr() Converts String to Upper case strchr() String scanning function strncat() Concatenates String with the part of another srtncmp() Compares the parts of two Strings strncpy() Copies a part of the String //Example 1#include<stdio.h> 2#include<string.h> 3int main( ) 4{ 5 6 7 8 9 10} //Output int len; char text[10]="saveetha" ; length = strlen(array) ; printf ( "string length is = %d n" , length ) ; return 0; string length is = 7 Functions
- 59. C PROGRAMMING 58 A Function can be defined as a subdivided program of the main program enclosed within flower brackets. Functions can be called by the main program to implement its functionality. This procedure provides Code Re-usability and Modularity. Two types of Functions are: Library Functions User-Defined Functions Advantages of Functions Writing the same code repeatedly in a program will be avoided. Functions can be called any number of times in a program. Tracking a C program easily when it is divided into multiple functions. Reusability is the main achievement of C functions. Rules to be followed to use functions: Function Declaration A function is required to declared as Global and the name of the function, parameters of the function and return type of the function are required to be clearly specified. Function Call While calling the function from anywhere in the program, care should be taken that the datatype in the argument list and the number of elements in the argument list are matching. Function Definition After the function is declared, it is important that the function includes parameters declared, code segment, and the return value. SN C function aspects Syntax 1 Function declaration return_type function_name (argument list); 2 Function call function_name (argument_list) 3 Function definition return_type function_name (argument list) {function body;} Four Aspects of using Functions in C Programming Function without arguments and without return value Function without arguments and with the return value Function with arguments and without return value Function with arguments and with the return value
- 60. C PROGRAMMING 59 Example for Function without argument and return value Example 1 #include<stdio.h> void printName(); void main () { printf("Hello "); printName(); } void printName() { printf("Javatpoint"); } Output Hello Javatpoint Example for Function without argument and with return value #include<stdio.h> int sum(); void main() { int result; printf("nGoing to calculate the sum of two numbers:"); result = sum(); printf("%d",result); } intsum() { inta,b; printf("nEnter two numbers"); scanf("%d %d",&a,&b); return a+b;
- 61. C PROGRAMMING 60 Going to calculate the sum of two numbers: Enter two numbers 10 24 The sum is 34 } Example for Function with argument and without return value #include<stdio.h> void sum(int,int); void main() { int a,b,result; printf("nGoing to calculate the sum of two numbers:"); printf("nEnter two numbers:"); scanf("%d%d",&a,&b); sum(a,b); } void sum(int a, int b) { printf("nThe sum is %d",a+b); } Output Example for Function with argument and with return value: #include<stdio.h> int even_odd(int); void main() { int n,flag=0; printf("nGoing to check whether a number is even orodd"); printf("nEnter the number: "); scanf("%d",&n); flag =even_odd(n); if(flag == 0) {
- 62. C PROGRAMMING 61 Going to check whether a number is even or odd Enter the number: 100 The number is even printf("nThe number is odd"); } else { printf("nThe number is even"); } } int even_odd(int n) { if(n%2 == 0) { return 1; } else { return 0; } } Output
- 63. C PROGRAMMING 62 Call by value and Call by reference in C There are two methods to pass the data into the function in C language, i.e., call by value and call by reference. Let's understand call by value and call by reference in c language one by one. Call by value in C o In call by value method, the value of the actual parameters is copied into the formal parameters. In other words, we can say that the value of the variable is used in the function call in the call by value method. o In call by value method, we can not modify the value of the actual parameter by the formal parameter. o In call by value, different memory is allocated for actual and formal parameters since the value of the actual parameter is copied into the formal parameter. o The actual parameter is the argument which is used in the function call whereas formal parameter is the argument which is used in the function definition. Let's try to understand the concept of call by value in c language by the example given below:
- 64. C PROGRAMMING 63 Before swapping the values in main a = 10, b = 20 After swapping values in function a = 20, b = 10 After swapping values in main a = 10, b = 20 Call by Value Example: Swapping the values of the two variables 1. #include <stdio.h> 2. void swap(int , int); //prototype of the function 3. int main() 4. { 5. int a = 10; 6. int b = 20; 7. printf("Before swapping the values in main a = %d, b = %dn",a,b); // printin g the value of a and b in main 8. swap(a,b); 9. printf("After swapping values in main a = %d, b = %dn",a,b); 10. void swap (int a, int b) 11. { 12. int temp; 13. temp = a; 14. a=b; 15. b=temp; 16.printf("After swapping values in function a = %d, b = %dn",a,b); // Form al parameters, a = 20, b = 10 17. } Output Call by reference in C o In call by reference, the address of the variable is passed into the function call as the actual parameter. o The value of the actual parameters can be modified by changing the formal parameters since the address of the actual parameters is passed. o In call by reference, the memory allocation is similar for both formal parameters and actual parameters. All the operations in the function
- 65. C PROGRAMMING 64 Before swapping the values in main a = 10, b = 20 After swapping values in function a = 20, b = 10 After swapping values in main a = 20, b = 10 No. Callbyvalue Call by reference are performed on the value stored at the address of the actual parameters, and the modified value gets stored at the same address. Consider the following example for the call by reference. Swapping the values of the two variables 1. #include <stdio.h> 2. void swap(int *, int *); //prototype of the function 3. int main() 4. { 5. int a = 10; 6. int b = 20; 7. printf("Before swapping the values in main a = %d, b = %dn",a,b); // printing the value of a and b in main 8. swap(&a,&b); 9. printf("After swapping values in main a = %d, b = %dn",a,b); // The values of actual para meters do change in call by reference, a = 10, b = 20 10. } 11. void swap (int *a, int *b) 12. { 13. int temp; 14. temp = *a; 15. *a=*b; 16. *b=temp; 17. printf("After swapping values in function a = %d, b = %dn",*a,*b); // Formal parameters, a = 20, b = 10 18. } Output Difference between call by value and call by reference in c
- 66. C PROGRAMMING 65 1 A copy of the value is passed into the function An address of value is passed into the function 2 Changes made inside the function is limited to the function only. The values of the actual parameters do not change by changing the formal parameters. Changes made inside the function validate outside of the function also. The values of the actual parameters do change by changing the formal parameters. 3 Actual and formal arguments are created at the different memory location Actual and formal arguments are created at the same memory location Recursion in C Recursion is the process which comes into existence when a function calls a copy of itself to work on a smaller problem. Any function which calls itself is called recursive function, and such function calls are called recursive calls. Recursion involves several numbers of recursive calls. However, it is important to impose a termination condition of recursion. Recursion code is shorter than iterative code however it is difficult to understand. Recursion cannot be applied to all the problem, but it is more useful for the tasks that can be defined in terms of similar subtasks. For Example, recursion may be applied to sorting, searching, and traversal problems. Generally, iterative solutions are more efficient than recursion since function call is always overhead. Any problem that can be solved recursively, can also be solved iteratively. However, some problems are best suited to be solved by the recursion, for example, tower of Hanoi, Fibonacci series, factorial finding, etc.
- 67. C PROGRAMMING 66 Enter the number whose factorial you want to calculate?5 factorial = 120 In the following example, recursion is used to calculate the factorial of a number. 1. #include <stdio.h> 2. int fact (int); 3. int main() 4. { 5. int n,f; 6. printf("Enter the number whose factorial you want to calculate?"); 7. scanf("%d",&n); 8. f = fact(n); 9. printf("factorial = %d",f); 10. } 11. int fact(int n) 12. { 13. if (n==0) 14. { 15. return 0; 16. } 17. else if ( n == 1) 18. { 19. return 1; 20. } 21. else 22. { 23. return n*fact(n-1); 24. } 25. } Output
- 68. C PROGRAMMING 67 Example of recursion in C Let's see an example to find the nth term of the Fibonacci series. 1. #include<stdio.h> 2. int fibonacci(int); 3. void main () 4. { 5. int n,f; 6. printf("Enter the value of n?"); 7. scanf("%d",&n); 8. f = fibonacci(n); 9. printf("%d",f); 10. } 11. int fibonacci (int n) 12. { 13. if (n==0) 14. { 15. return 0; 16. } 17. else if (n == 1) 18. { 19. return 1; 20. }
- 69. C PROGRAMMING 68 Enter the value of n?12 144 21. else 22. { 23. return fibonacci(n-1)+fibonacci(n-2); 24. } 25. } Output Memory allocation of Recursive method Each recursive call creates a new copy of that method in the memory. Once some data is returned by the method, the copy is removed from the memory. Since all the variables and other stuff declared inside function get stored in the stack, therefore a separate stack is maintained at each recursive call. Once the value is returned from the corresponding function, the stack gets destroyed. Recursion involves so much complexity in resolving and tracking the values at each recursive call. Therefore we need to maintain the stack and track the values of the variables defined in the stack. Let us consider the following example to understand the memory allocation of the recursive functions. 1. int display (int n) 2. { 3. if(n == 0) 4. return 0; // terminating condition 5. else 6. { 7. printf("%d",n); 8. return display(n-1); // recursive call 9. } 10. }
- 70. C PROGRAMMING 69 Storage Classes in C Storage classes in C are used to determine the lifetime, visibility, memory location, and initial value of a variable. There are four types of storage classes in C o Automatic o External o Static o Register Storage Classes Storage Place Default Value Scope Lifetime auto RAM Garbage Value Local Within function extern RAM Zero Global Till the end of the main program Maybe declared anywhere in the program static RAM Zero Local Till the end of the main program, Retains value between multiple functions call register Register Garbage Value Local Within the function
- 71. C PROGRAMMING 70 Automatic o Automatic variables are allocated memory automatically at runtime. o The visibility of the automatic variables is limited to the block in which they are defined. The scope of the automatic variables is limited to the block in which they are defined. o The automatic variables are initialized to garbage by default. o The memory assigned to automatic variables gets freed upon exiting from the block. o The keyword used for defining automatic variables is auto. o Every local variable is automatic in C by default. Example 1 1. #include <stdio.h> 2. int main() 3. { 4. int a; //auto 5. char b; 6. float c; 7. printf("%d %c %f",a,b,c); // printing initial default value of automatic variables a, b, and c. 8. return 0; 9. } Output: garbage garbage garbage Example 2 1. #include <stdio.h> 2. int main() 3. { 4. int a = 10,i; 5. printf("%d ",++a); 6. { 7. int a = 20; 8. for (i=0;i<3;i++) 9. { 10. printf("%d ",a); // 20 will be printed 3 times since it is the local value of a
- 72. C PROGRAMMING 71 11. } 12. } 13. printf("%d ",a); // 11 will be printed since the scope of a = 20 is ended. 14. } Output: 11 20 20 20 11 Static o The variables defined as static specifier can hold their value between the multiple function calls. o Static local variables are visible only to the function or the block in which they are defined. o A same static variable can be declared many times but can be assigned at only one time. o Default initial value of the static integral variable is 0 otherwise null. o The visibility of the static global variable is limited to the file in which it has declared. o The keyword used to define static variable is static. Example 1 1. #include<stdio.h> 2. static char c; 3. static int i; 4. static float f; 5. static char s[100]; 6. void main () 7. { 8. printf("%d %d %f %s",c,i,f); // the initial default value of c, i, and f will be printed. 9. } Output: 0 0.000000 (null) Example 2 1. #include<stdio.h> 2. void sum() 3. { 4. static int a = 10; 5. static int b = 24; 6. printf("%d %d n",a,b); 7. a++;
- 73. C PROGRAMMING 72 10 24 11 25 12 26 8. b++; 9. } 10. void main() 11. { 12. int i; 13. for(i = 0; i< 3; i++) 14. { 15. sum(); // The static variables holds their value between multiple function calls. 16. } 17. } Output: Register o The variables defined as the register is allocated the memory into the CPU registers depending upon the size of the memory remaining in the CPU. o We can not dereference the register variables, i.e., we can not use &operator for the register variable. o The access time of the register variables is faster than the automatic variables. o The initial default value of the register local variables is 0. o The register keyword is used for the variable which should be stored in the CPU register. However, it is compiler?s choice whether or not; the variables can be stored in the register. o We can store pointers into the register, i.e., a register can store the address of a variable. o Static variables can not be stored into the register since we can not use more than one storage specifier for the same variable. Example 1 1. #include <stdio.h> 2. int main() 3. { 4. register int a; // variable a is allocated memory in the CPU register. The initial default value of a is 0. 5. printf("%d",a); 6. }
- 74. C PROGRAMMING 73 main.c:5:5: error: address of register variable ?a? requested printf("%u",&a); ^~~~~~ Output: 0 Example 2 1. #include <stdio.h> 2. int main() 3. { 4. register int a = 0; 5. printf("%u",&a); // This will give a compile time error since we can not access the address of a register variable. 6. } Output: External o The external storage class is used to tell the compiler that the variable defined as extern is declared with an external linkage elsewhere in the program. o The variables declared as extern are not allocated any memory. It is only declaration and intended to specify that the variable is declared elsewhere in the program. o The default initial value of external integral type is 0 otherwise null. o We can only initialize the extern variable globally, i.e., we can not initialize the external variable within any block or method. o An external variable can be declared many times but can be initialized at only once. o If a variable is declared as external then the compiler searches for that variable to be initialized somewhere in the program which may be extern or static. If it is not, then the compiler will show an error. Example 1 1. #include <stdio.h> 2. int main() 3. { 4. extern int a; 5. printf("%d",a); 6. } Output
- 75. C PROGRAMMING 74 compile time error main.c: In function ?main?: main.c:5:16: error: ?a? has both ?extern? and initializer extern int a = 0; Example 2 1. #include <stdio.h> 2. int a; 3. int main() 4. { 5. extern int a; // variable a is defined globally, the memory will not be allocated to a 6. printf("%d",a); 7. } Output 0 Example 3 1. #include <stdio.h> 2. int a; 3. int main() 4. { 5. extern int a = 0; // this will show a compiler error since we can not use extern and initializer at same time 6. printf("%d",a); 7. } Output Example 4 1. #include <stdio.h> 2. int main() 3. { 4. extern int a; // Compiler will search here for a variable a defined and initialized somewhere in the p ogram or not. 5. printf("%d",a); 6. } 7. int a = 20; Output 20 main.c:(.text+0x6): undefined reference to `a' collect2: error: ld returned 1 exit status
- 76. C PROGRAMMING 75 Example 5 1. extern int a; 2. int a = 10; 3. #include <stdio.h> 4. int main() 5. { 6. printf("%d",a); 7. } 8. int a = 20; // compiler will show an error at this line Output compile time error compile time error C Library Functions Library functions are the inbuilt function in C that are grouped and placed at a common place called the library. Such functions are used to perform some specific operations. For example,printf is a library function used to print on the console. The library functions are created by the designers of compilers. All C standard library functions are defined inside the different header files saved with the extension .h. We need to include these header files in our program to make use of the library functions defined in such header files. For example, To use the library functions such as printf/scanf we need to include stdio.h in our program which is a header file that contains all the library functions regarding standard input/output. The list of mostly used header files is given in the following table. SN Header file Description 1 stdio.h This is a standard input/output header file. It contains all the library functions regarding standard input/output. 2 conio.h This is a console input/output header file. 3 string.h It contains all string related library functions like gets(), puts(),etc. 4 stdlib.h This header file contains all the general library functions like malloc(), calloc(), exit(), etc. 5 math.h This header file contains all the math operations related functions like sqrt(), pow(), etc.
- 77. C PROGRAMMING 76 #include <stdio.h> int main( int argc, char *argv[] ) { if( argc == 2 ) { printf("The argument supplied is %sn", argv[1]); } else if( argc > 2 ) { printf("Too many arguments supplied.n"); } else { printf("One argument expected.n"); } } $./a.out testing The argument supplied is testing 6 time.h This header file contains all the time-related functions. 7 ctype.h This header file contains all character handling functions. 8 stdarg.h Variable argument functions are defined in this header file. 9 signal.h All the signal handling functions are defined in this header file. 10 setjmp.h This file contains all the jump functions. 11 locale.h This file contains locale functions. 12 errno.h This file contains error handling functions. 13 assert.h This file contains diagnostics functions. Command line arguments: It is possible to pass some values from the command line to your C programs when they are executed. These values are called command line arguments and many times they are important for your program especially when you want to control your program from outside instead of hard coding those values inside the code. The command line arguments are handled using main() function arguments where argc refers to the number of arguments passed, and argv[] is a pointer array which points to each argument passed to the program. Following is a simple example which checks if there is any argument supplied from the command line and take action accordingly − When the above code is compiled and executed with single argument, it produces the following result.
- 78. C PROGRAMMING 77 $./a.out testing1 testing2 Too many arguments supplied. $./a.out One argument expected #include <stdio.h> int main( int argc, char *argv[] ) { printf("Program name %sn", argv[0]); if( argc == 2 ) { printf("The argument supplied is %sn", argv[1]); } else if( argc > 2 ) { printf("Too many arguments supplied.n"); } else { printf("One argument expected.n"); } } $./a.out "testing1 testing2" Program name ./a.out The argument supplied is testing1 testing2 When the above code is compiled and executed with a two arguments, it produces the following result. When the above code is compiled and executed without passing any argument, it produces the following result. It should be noted that argv[0] holds the name of the program itself and argv[1] is a pointer to the first command line argument supplied, and *argv[n] is the last argument. If no arguments are supplied, argc will be one, and if you pass one argument then argc is set at 2. You pass all the command line arguments separated by a space, but if argument itself has a space then you can pass such arguments by putting them inside double quotes "" or single quotes ''. Let us re-write above example once again where we will print program name and we also pass a command line argument by putting inside double quotes − When the above code is compiled and executed with a single argument separated by space but inside double quotes, it produces the following result.
- 79. C PROGRAMMING 78 What is Pointer in C? Pointer in C ThePointerinC,isavariablethatstoresaddressofanothervariable.Apointercanalsobe used to refer to another pointer function. A pointer can be incremented/decremented, i.e., to pointtothenext/previousmemorylocation.Thepurposeofpointeristosavememory space and achieve faster execution time. How to Use Pointers in C If we declare a variable v of type int, v will actually store a value. v is equal to zero now. However,eachvariable,apartfromvalue,alsohasitsaddress(or,simplyput,whereitis located in the memory). The address can be retrieved by putting an ampersand (&) before the variable name. Ifyouprinttheaddressofavariableonthescreen,itwilllooklikeatotallyrandomnumber (moreover, it can be different from run to run). Let’s try this in practice with pointer in C example The output of this program is -480613588. Now,whatisapointer?Insteadofstoringavalue,apointerwillystoretheaddressofa variable.
- 80. C PROGRAMMING 79 Pointer Variable Int *y = &v; VARIABLE POINTER Avaluestoredinanamedstorage/memoryaddress Avariablethatpointstothestorage/mem ofanother variable Declaring a Pointer Likevariables,pointersinCprogramminghavetobedeclaredbeforetheycanbeusedin your program. Pointers can be named anything you want as long as they obey C’s naming rules. A pointer declaration has the following form. data_type * pointer_variable_name; Here, data_typeisthepointer’sbasetypeofC’svariabletypesandindicatesthetypeofthe variable that the pointer points to. The asterisk (*: the same asterisk used for multiplication) which is indirection operator, declares a pointer. Let’ssee some validpointer declarationsin this C pointers tutorial: int *ptr_thing; /* pointer to an integer */ int *ptr1,thing;/* ptr1 is a pointer to type integer and thing is an integer variable */ double *ptr2; /* pointer to a double */ float *ptr3; /* pointer to a float */ char *ch1 ; /* pointer to a character */ float *ptr, variable;/*ptr is a pointer to type float and variable is an ordinary float variable */ Initialize a pointer After declaring a pointer, we initialize it like standard variables with a variable address. If pointersinCprogrammingarenotuninitializedandusedintheprogram,theresultsare unpredictable and potentially disastrous. To get the address of a variable, we use the ampersand (&)operator, placed before the name of a variable whose address we need. Pointer initialization is done with the following syntax. Pointer Syntax
- 81. C PROGRAMMING 80 Serves only 1 purpose & Returns the address of a variable pointer = &variable; A simple program for pointer illustration is given below: #include <stdio.h> int main() { int a=10; //variable declaration int *p; //pointer variable declaration p=&a; //store address of variable a in pointer p printf("Address stored in a variable p is:%xn",p); //accessing the address printf("Value stored in a variable p is:%dn",*p); //accessing the value return 0; } Output: Address stored in a variable p is:60ff08 Value stored in a variable p is:10 Serves 2 purpose * 1. Declaration of a pointer 2. Returns the value of the referenced variable Types of Pointers in C Following are the different Types of Pointers in C: Operator Meaning
- 82. C PROGRAMMING 81 1. Null Pointer Wecancreateanullpointerbyassigningnullvalueduringthepointerdeclaration.This methodisusefulwhenyoudonothaveanyaddressassignedtothepointer.Anullpointer always contains value 0. Following program illustrates the use of a null pointer: #include <stdio.h> int main() { } Output: int *p = NULL; //null pointer printf(“The value inside variable p is:n%x”,p); return 0; The value inside variable p is: 0 2. Void Pointer InCprogramming,avoidpointerisalsocalledasagenericpointer.Itdoesnothaveany standarddatatype.Avoidpointeriscreatedbyusingthekeywordvoid.Itcanbeusedto store an address of any variable. Following program illustrates the use of a void pointer: #include <stdio.h> int main() { void *p = NULL; //void pointer printf("The size of pointer is:%dn",sizeof(p)); return 0; } Output: The size of pointer is:4 3.Wild pointer Apointerissaidtobeawildpointerifitisnotbeinginitializedtoanything.ThesetypesofC pointers are not efficient because they may point to some unknown memory location which maycauseproblemsinourprogramanditmayleadtocrashingoftheprogram.Oneshould always be careful while working with wild pointers. Following program illustrates the use of wild pointer:
- 83. C PROGRAMMING 82 #include <stdio.h> int main() { int *p; //wild pointer printf("n%d",*p); return 0; } Output timeout: the monitored command dumped core sh: line 1: 95298 Segmentation fault timeout 10s main Other types of pointers in ‘c’ are as follows: Dangling pointer Complex pointer Near pointer Far pointer Huge pointer Direct and Indirect Access Pointers InC,therearetwoequivalentwaystoaccessandmanipulateavariablecontent Direct access: we use directly the variable name Indirect access: we use a pointer to the variable Let’sunderstandthiswiththehelpofprogrambelow #include <stdio.h> /* Declare and initialize an int variable */ int var = 1; /* Declare a pointer to int */ int *ptr; int main( void ) { /* Initialize ptr to point to var */ ptr = &var; /* Access var directly and indirectly */ printf("nDirect access, var = %d", var); printf("nIndirect access, var = %d", *ptr); /* Display the address of var two ways */ printf("nnThe address of var = %d", &var); printf("nThe address of var = %dn", ptr); /*change the content of var through the pointer*/ *ptr=48;
- 84. C PROGRAMMING 83 printf("nIndirect access, var = %d", *ptr); return 0;} After compiling the program without any errors, the result is: Direct access, var = 1 Indirect access, var = 1 The address of var = 4202496 The address of var = 4202496 Indirect access, var = 48 Pointer Arithmetics inC The pointer operations are summarized in the following figure Pointer Operations
- 85. C PROGRAMMING Priority operation (precedence) WhenworkingwithCpointers,wemustobservethefollowingpriorityrules: The operators * and & have the same priority as the unary operators (the negation!, the incrementation++, decrement–). Inthesameexpression,theunaryoperators*,&,!,++,–areevaluatedfromrighttoleft. IfaPpointerpointstoanXvariable,then*PcanbeusedwhereverXcanbewritten. The following expressions are equivalent: int X =10 int*P=&Y; For the above code, below expressions are true Expression Equivalent Expression Y=*P+1 Y=X+1 *P=*P+10 X=X+10 *P+=2 X+=2 ++*P ++X (*P)++ X++ Inthelattercase,parenthesesareneeded:astheunaryoperators*and++areevaluated fromrighttoleft,withouttheparenthesesthepointerPwouldbeincremented,notthe object on which P points. BelowtableshowsthearithmeticandbasicoperationthatcanbeusedwhendealingwithC pointers Operation Explanation int *P1,*P2 Assignment P1=P2; P1andP2pointtothesameintegervariable 84
- 86. C PROGRAMMING 85 Adding an offset(Constant) ThisallowsthepointertomoveNelements in a table. Thepointerwillbeincreasedordecreased byNtimesthenumberofbyte(s)ofthetype of the variable. P1+5; Incrementation anddecrementation Int *P1; P1++;P1–;
- 87. C PROGRAMMING 86 C Pointers & Arrays with Examples Traditionally, we access the array elements using its index, but this method can be eliminated by using pointers. Pointers make it easy to access each array element. #include <stdio.h> int main() { int a[5]={1,2,3,4,5}; //array initialization int *p; //pointer declaration /*the ptr points to the first element of the array*/ p=a; /*We can also type simply ptr==&a[0] */ printf("Printing the array elements using pointern"); for(int i=0;i<5;i++) //loop for traversing array elements { printf("n%x",*p); //printing array elements p++; //incrementing to the next element, you can also write p=p+1 } return 0; } Output 1 2 3 4 5 Addingaparticularnumbertoapointerwillmovethepointerlocationtothevalue obtainedbyanadditionoperation.Supposepisapointerthatcurrentlypointstothe memorylocation0ifweperformfollowingadditionoperation,p+1thenitwillexecuteinthis manner: Pointer Addition/Increment Sincepcurrentlypointstothelocation0afteradding1,thevaluewillbecome1,andhence the pointer will point to the memory location 1.
- 88. C PROGRAMMING 87 C Pointers and Strings with Examples Astringisanarrayofcharobjects,endingwithanullcharacter‘0’.Wecanmanipulate stringsusingpointers.ThispointerinCexampleexplainsthissection #include <stdio.h> #include <string.h> int main() { char str[]="Hello Guru99!"; char *p; p=str; printf("First character is:%cn",*p); p =p+1; printf("Next character is:%cn",*p); printf("Printing all the characters in a stringn"); p=str; //reset the pointer for(int i=0;i<strlen(str);i++) { printf("%cn",*p); p++; } return 0; } Output First character is:H Next character is:e Printing all the characters in a string H e l l o G u r u 9 9 ! Anotherwaytodealstringsiswithanarrayofpointerslikeinthefollowingprogram: #include <stdio.h> int main(){ char *materials[ ] = { "iron", "copper", "gold"}; printf("Please remember these materials :n"); int i ; for (i = 0; i < 3; i++) { printf("%sn", materials[ i ]);} return 0;}
- 89. C PROGRAMMING 88 Advantages of Pointers in C Pointers are useful for accessing memory locations. Pointersprovideanefficientwayforaccessingtheelementsofanarraystructure. Pointersareusedfordynamicmemoryallocationaswellasdeallocation. Pointersareusedtoformcomplexdatastructuressuchaslinkedlist,graph,tree,etc. Disadvantages of Pointers inC Pointers are a little complex to understand. Pointers can lead to various errors such as segmentation faults or can access a memory location which is not required at all. Ifanincorrectvalueisprovidedtoapointer,itmaycausememorycorruption. Pointers are also responsible for memory leakage. Pointersare comparatively slower than that of the variables. Programmers find it very difficult to work with the pointers; therefore it is programmer’sresponsibilitytomanipulateapointercarefully. Summary: Apointer is nothing buta memory location where data is stored. A pointer is used to access the memory location. Therearevarioustypesofpointerssuchasanullpointer,wildpointer,voidpointer and other types of pointers. Pointerscanbeusedwitharrayandstringtoaccesselementsmoreefficiently. We can create functionpointerstoinvokeafunctiondynamically. Arithmeticoperationscanbedoneonapointerwhichisknownaspointerarithmetic. Pointerscanalsopointtofunctionwhichmakeiteasytocalldifferentfunctionsinthe case of defining an array of pointers. Whenyouwanttodealdifferentvariabledatatype,youcanuseatypecastvoid pointer.
- 90. C PROGRAMMING 89 What is Structure? Structure and Union Structure in c is a user-defined data type that enables us to store the collection of different data types. Each element of a structure is called a member. Structures ca; simulate the use of classes and templates as it can store various information The ,struct keyword is used to define the structure. Let's see the syntax to define the structure in c. struct structure_name { data_type member1; data_type member2; . . data_type memeberN; }; The following image shows the memory allocation of the structure employee that is defined in the above example.
- 91. C PROGRAMMING 90 Here, struct is the keyword; employee is the name of the structure; id, name, and salary are the members or fields of the structure. Let's understand it by the diagram given below: Declaring structure variable We can declare a variable for the structure so that we can access the member of the structure easily. There are two ways to declare structure variable: 1. By struct keyword within main() function 2. By declaring a variable at the time of defining the structure. 1st way: Let's see the example to declare the structure variable by struct keyword. It should be declared within the main function. struct employee { int id; char name[50]; float salary; }; Now write given code inside the main() function. 1. struct employee e1, e2;
- 92. C PROGRAMMING 91 The variables e1 and e2 can be used to access the values stored in the structure. Here, e1 and e2 can be treated in the same way as the objects in C++ and Java. 2nd way: Let's see another way to declare variable at the time of defining the structure. struct employee { int id; char name[50]; float salary; }e1,e2; Which approach is good If number of variables are not fixed, use the 1st approach. It provides you the flexibility to declare the structure variable many times. Accessing members of the structure There are two ways to access structure members: 1. By . (member or dot operator) 2. By -> (structure pointer operator) Let's see the code to access the id member of p1 variable by. (member) operator. p1.id C Structure example Let's see a simple example of structure in C language. 1. #include<stdio.h> 2. #include <string.h> 3. struct employee 4. { int id; 5. char name[50]; 6. }e1; //declaring e1 variable for structure
- 93. C PROGRAMMING 92 employee 1 id : 101 employee 1 name : Sonoo Jaiswal 7. int main( ) 8. { 9. //store first employee information 10. e1.id=101; 11. strcpy(e1.name, "Sonoo Jaiswal");//copying string into char array 12. //printing first employee information 13. printf( "employee 1 id : %dn", e1.id); 14. printf( "employee 1 name : %sn", e1.name); 15. return 0; 16. } Output: Let's see another example of the structure in C language to store many employees information. 1. #include<stdio.h> 2. #include <string.h> 3. struct employee 4. { int id; 5. char name[50]; 6. float salary; 7. }e1,e2; //declaring e1 and e2 variables for structure 8. int main( ) 9. { 10. //store first employee information 11. e1.id=101; 12. strcpy(e1.name, "Sonoo Jaiswal");//copying string into char array 13. e1.salary=56000; 14. 15. //store second employee information 16. e2.id=102; 17. strcpy(e2.name, "James Bond"); 18. e2.salary=126000; 19. 20. //printing first employee information
- 94. C PROGRAMMING 93 employee 1 id : 101 employee 1 name : Sonoo Jaiswal employee 1 salary : 56000.000000 employee 2 id : 102 employee 2 name : James Bond employee 2 salary : 126000.000000 21. printf( "employee 1 id : %dn", e1.id); 22. printf( "employee 1 name : %sn", e1.name); 23. printf( "employee 1 salary : %fn", e1.salary); 24. 25. //printing second employee information 26. printf( "employee 2 id : %dn", e2.id); 27. printf( "employee 2 name : %sn", e2.name); 28. printf( "employee 2 salary : %fn", e2.salary); 29. return 0; 30. } Output: typedef in C The typedef is a keyword used in C programming to provide some meaningful names to the already existing variable in the C program .Itbehavessimilarlyaswedefinethealiasforthecommands.Inshort,wecansaythatthis keyword is used to redefine the name of an already existing variable. Syntax of typedef typedef <existing_name> <alias_name> In the above syntax, 'existing_name' is the name of an already existing variable while 'alias name' is another name given to the existing variable. For example, suppose we want to create a variable of type unsigned int, then it becomes a tedious task if we want to declare multiple variables of this type. To overcome the problem, we use a typedef keyword. typedef unsigned int unit;
- 95. C PROGRAMMING 94 Now, we can create the variables of type unsigned int by writing the following statement: unit a, b; instead of writing: unsigned int a, b; Let's understand through a simple example. 1. #include <stdio.h> 2. int main() 3. { 4. typedef unsigned int unit; 5. unit i,j; 6. i=10; 7. j=20; 8. printf("Value of i is :%d",i); 9. printf("nValue of j is :%d",j); 10. return 0; 11. } Output Value of i is :10 Value of j is :20 Using typedef with structures Consider the below structure declaration: struct student { char name[20]; int age;
- 96. C PROGRAMMING 95 }; struct student s1; In the above structure declaration, we have created the variable of student type by writing the following statement: struct student s1; The above statement shows the creation of a variable, i.e., s1, but the statement is quite big. To avoid such a big statement, we use the typedef keyword to create the variable of type student. struct student { char name[20]; int age; }; typedef struct student stud; stud s1, s2; In the above statement, we have declared the variable stud of type struct student. Now, we can use the stud variable in a program to create the variables of type struct student. The above typedef can be written as: typedef struct student { char name[20]; int age; } stud; stud s1,s2; From the above declarations, we conclude that typedef keyword reduces the length of the code and complexity of data types. It also helps in understanding the program. Let's see another example where we typedef the structure declaration.
- 97. C PROGRAMMING 96 #include <stdio.h> typedef struct student { char name[20]; int age; }stud; int main() { stud s1; printf("Enter the details of student s1: "); printf("nEnter the name of the student:"); scanf("%s",&s1.name); printf("nEnter the age of student:"); scanf("%d",&s1.age); printf("n Name of the student is : %s", s1.name); printf("n Age of the student is : %d", s1.age); return 0; } Enter the details of student s1: Enter the name of the student: Peter Enter the age of student: 28 Name of the student is : Peter Age of the student is : 28 Using typedef with pointers We can also provide another name or alias name to the pointer variables with the help of the typedef. For example, we normally declare a pointer, as shown below:
- 98. C PROGRAMMING 97 1. int* ptr; We can rename the above pointer variable as given below: 1. typedef int* ptr; In the above statement, we have declared the variable of type int*. Now, we can create the variable of type int* by simply using the 'ptr' variable as shown in the below statement: 1. ptr p1, p2 ; In the above statement, p1 and p2 are the variables of type 'ptr'. C Array of Structures Why use an array of structures? Consider a case, where we need to store the data of 5 students. We can store it by using the structure as given below. 1. #include<stdio.h> 2. struct student 3. { 4. char name[20]; 5. int id; 6. float marks; 7. }; 8. void main() 9. { 10. struct student s1,s2,s3; 11. int dummy; 12. printf("Enter the name, id, and marks of student 1 "); 13. scanf("%s %d %f",s1.name,&s1.id,&s1.marks); 14. scanf("%c",&dummy);
- 99. C PROGRAMMING 98 Enter the name, id, and marks of student 1 James 90 90 Enter the name, id, and marks of student 2 Adoms 90 90 Enter the name, id, and marks of student 3 Nick 90 90 Printing the details.... James 90 90.000000 Adoms 90 90.000000 Nick 90 90.000000 15. printf("Enter the name, id, and marks of student 2 "); 16. scanf("%s %d %f",s2.name,&s2.id,&s2.marks); 17. scanf("%c",&dummy); 18. printf("Enter the name, id, and marks of student 3 "); 19. scanf("%s %d %f",s3.name,&s3.id,&s3.marks); 20. scanf("%c",&dummy); 21. printf("Printing the details...n"); 22. printf("%s %d%fn",s1.name,s1.id,s1.marks); 23. printf("%s %d%fn",s2.name,s2.id,s2.marks); 24. printf("%s %d%fn",s3.name,s3.id,s3.marks); 25. } Output In the above program, we have stored data of 3 students in the structure. However, the complexity of the program will be increased if there are 20 students. In that case, we will have to declare 20 different structure variables and store them one by one. This will always be tough since we will have to declare a variable every time we add a student. Remembering the name of all the variables is also a very tricky task. However, c enables us to declare an array of structures by using which, we can avoid declaring the different structure variables; instead we can make a collection containing all the structures that store the information of different entities. Array of Structures in C An array of structures in C can be defined as the collection of multiple structures variables where each variable contains information about different entities. The array of structures in C are used to store information about multiple entities of different data types. The array of structures is also known as the collection of structures.
- 100. C PROGRAMMING 99 Let's see an example of an array of structures that stores information of 5 students and prints it. #include<stdio.h> #include <string.h> struct student{ int rollno; char name[10]; }; int main(){ int i; struct student st[5]; printf("Enter Records of 5 students"); for(i=0;i<5;i++){ printf("nEnter Rollno:"); scanf("%d",&st[i].rollno); printf("nEnter Name:"); scanf("%s",&st[i].name); } printf("nStudent Information List:"); for(i=0;i<5;i++){ printf("nRollno:%d, Name:%s",st[i].rollno,st[i].name);
- 101. C PROGRAMMING 100 Enter Records of 5 students Enter Rollno:1 Enter Name:Sonoo Enter Rollno:2 Enter Name:Ratan Enter Rollno:3 Enter Name:Vimal Enter Rollno:4 Enter Name:James Enter Rollno:5 Enter Name:Sarfraz Student Information List: Rollno:1, Name:Sonoo Rollno:2, Name:Ratan Rollno:3, Name:Vimal Rollno:4, Name:James Rollno:5, Name:Sarfraz } return 0; } Output: Passing structure to function Just like other variables, a structure can also be passed to a function. We may pass the structure members into the function or pass the structure variable at once. Consider the following example to pass the structure variable employee to a function display() which is used to display the details of an employee. #include<stdio.h> struct address { char city[20]; int pin; char phone[14]; }; struct employee { char name[20]; struct address add; };
- 102. C PROGRAMMING 101 void display(struct employee); void main () { struct employee emp; printf("Enter employee information?n"); scanf("%s %s %d %s",emp.name,emp.add.city, &emp.add.pin, emp.add.phone); display(emp); } void display(struct employee emp) { printf("Printing the details ...n"); printf("%s %s %d %s",emp.name,emp.add.city,emp.add.pin,emp.add.phone); Union A union is a special data type available in C that allows storing different data types in the same memory location. union is the keyword used to declare Union. Union can be defined as a user-defined data type which is a collection of different variables of different data types in the same memory location. The union can also be defined as many members, but only one member can contain a value at a particular point in time. Union is a user-defined data type, but unlike structures, they share the same memory location. //Example 1#include<stdio.h> 2union Employee 3{
- 103. C PROGRAMMING 102 4 5 6 7 8}; int Id; char Name[25]; int Age; long Salary; 9void main() 10{ 11 12 13 14 15 16 17 18 19 20 21 22 23 24} //Output union Employee E; printf("nEnter Employee Id : "); scanf("%d",&E.Id); printf("nEnter Employee Name : "); scanf("%s",&E.Name); printf("nEnter Employee Age : "); scanf("%d",&E.Age); printf("nEnter Employee Salary : "); scanf("%ld",&E.Salary); printf("nnEmployee Id : %d",E.Id); printf("nEmployee Name : %s",E.Name); printf("nEmployee Age : %d",E.Age); printf("nEmployee Salary : %ld",E.Salary); Enter Employee Id : 102191 Enter Employee Name : Karan Enter Employee Age : 29 Enter Employee Salary : 45000 Employee Id : 102011 Employee Name : Ajay Employee Age : 26 Employee Salary : 45000 Accessing members of union using pointers We can access the members of the union through pointers by using the (->) arrow operator. Let's understand through an example.
- 104. C PROGRAMMING 103 Parameter Structure Union #include <stdio.h> union abc { int a; char b; }; int main() { union abc *ptr; // pointer variable declaration union abc var; var.a= 90; ptr = &var; printf("The value of a is : %d", ptr->a); return 0; } In the above code, we have created a pointer variable, i.e., *ptr, that stores the address of var variable. Now, ptr can access the variable 'a' by using the (->) operator. Hence the output of the above code would be 90. Difference between Structure and Union Keyword struct union Memory Each member has a unique Memory All members share allocated Memory Initialization All members areinitialized together Only first member can be initialized Data Access All members is accessed together One member is accessed at a time
- 105. C PROGRAMMING 104 Value Change Changing the value of one member will not affect others Changing the value of one member will affect others
- 106. C PROGRAMMING File Handling in C In programming, we may require some specific input data to be generated several numbers of times. Sometimes, it is not enough to only display the data on the console. The data to be displayed may be very large, and only a limited amount of data can be displayed on the console, and since the memory is volatile, it is impossible to recover the programmatically generated data again and again. However, if we need to do so, we may store it onto the local file system which is volatile and can be accessed every time. Here, comes the need of file handling in C. File handling in C enables us to create, update, read, and delete the files stored on the local file system through our C program. The following operations can be performed on a file. o Creation of the newfile o Opening an existing file o Reading from the file o Writing to the file o Deleting the file Functions for file handling There are many functions in the C library to open, read, write, search and close the file. A list of file functions are given below: No. Function Description 1 fopen() opens new or existing file 2 fprintf() write data into the file 3 fscanf() reads data from the file 4 fputc() writes a character into the file 5 fgetc() reads a character from file 6 fclose() closes the file 105
- 107. C PROGRAMMING 7 fseek() 8 fputw() 9 fgetw() 10 ftell() 11 rewind() sets the file pointer to given position writes an integer to file reads an integer from file returns current position sets the file pointer to the beginning of the file Opening File: fopen() We must open a file before it can be read, write, or update. The fopen() function is used to open a file. The syntax of the fopen() is given below. 1. FILE *fopen( const char * filename, const char * mode); The fopen() function accepts two parameters: o The file name (string). If the file is stored at some specific location, then we must mention the path at which the file is stored. For example, a file name can be like "c://some_folder/some_file.ext". o The mode in which the file is to be opened. It is a string. We can use one of the following modes in the fopen() function. Mode Description r opens a text file in read mode w opens a text file in write mode a opens a text file in append mode r+ opens a text file in read and write mode w+ opens a text file in read and write mode 106
- 108. C PROGRAMMING a+ opens a text file in read and write mode rb opens a binary file in read mode wb opens a binary file in write mode ab opens a binary file in append mode rb+ opens a binary file in read and write mode wb+ opens a binary file in read and write mode ab+ opens a binary file in read and write mode The fopen function works in the following way. o Firstly, It searches the file to be opened. o Then, it loads the file from the disk and place it into the buffer. The buffer is used to provide efficiency for the read operations. o It sets up a character pointer which points to the first character of the file. Consider the following example which opens a file in write mode. 1. #include<stdio.h> 2. void main( ) 3. { 4. FILE *fp ; 5. char ch ; 6. fp = fopen("file_handle.c","r") ; 7. while ( 1 ) 8. { 9. ch = fgetc ( fp ) ; 10. if ( ch == EOF ) 11. break ; 12. printf("%c",ch) ; 107
- 109. C PROGRAMMING 108 #include; void main( ) { FILE *fp; // file pointer char ch; fp = fopen("file_handle.c","r"); while ( 1 ) { ch = fgetc ( fp ); //Each character of the file is read and stored in the character file. if ( ch == EOF ) break; printf("%c",ch); } fclose (fp ); } 13. } 14. fclose (fp ) ; 15. } Output The content of the file will be printed. Closing File: fclose() The fclose() function is used to close a file. The file must be closed after performing all the operations on it. The syntax of fclose() function is given below: int fclose( FILE *fp ); Writing File : fprintf() function The fprintf() function is used to write set of characters into file. It sends formatted output to a stream. Syntax: int fprintf(FILE *stream, const char *format [, argument, ...])
- 110. C PROGRAMMING 109 Example: 1. #include <stdio.h> 2. main(){ 3. FILE *fp; 4. fp = fopen("file.txt", "w");//opening file 5. fprintf(fp, "Hello file by fprintf...n");//writing data into file 6. fclose(fp);//closing file 7. } Reading File : fscanf() function The fscanf() function is used to read set of characters from file. It reads a word from the file and returns EOF at the end of file. Syntax: int fscanf(FILE *stream, const char *format [, argument, ...]) Example: 1. #include <stdio.h> 2. main(){ 3. FILE *fp; 4. char buff[255];//creating char array to store data of file 5. fp = fopen("file.txt", "r"); 6. while(fscanf(fp, "%s", buff)!=EOF){ 7. printf("%s ", buff ); 8. } 9. fclose(fp); 10. } Output: Hello file by fprintf...
- 111. C PROGRAMMING 110 This is sonoo Jaiswal C fseek() function The fseek() function is used to set the file pointer to the specified offset. It is used to write data into file at desired location. Syntax: int fseek(FILE *stream, long int offset, int whence) There are 3 constants used in the fseek() function for whence: SEEK_SET, SEEK_CUR and SEEK_END. 1. #include <stdio.h> 2. void main(){ 3. FILE *fp; 4. 5. fp = fopen("myfile.txt","w+"); 6. fputs("This is javatpoint", fp); 7. 8. fseek( fp, 7, SEEK_SET ); 9. fputs("sonoo jaiswal", fp); 10. fclose(fp); 11. } myfile.txt C rewind() function The rewind() function sets the file pointer at the beginning of the stream. It is useful if you have to use stream many times. Syntax: void rewind(FILE *stream)
- 112. C PROGRAMMING 111 The ftell() function returns the current file position of the specified stream. We can use ftell() function to get the total size of a file after moving file pointer at the end of file. We can use SEEK_END constant to move the file pointer at the end of file. Syntax: 1. long int ftell(FILE *stream)