C programming

Programming for
Problem Solving
Arnab Gain
28-07-2022
15:08
1

Programming, Algorithm, Flowchart,
Pseudocode
• Programming is the process of creating a set of instructions that tell a computer
how to perform a task.
• An Algorithm is a finite sequence of instructions, each of which has a clear
meaning and can be performed with a finite amount of effort in a finite length of
time.
• A flowchart is simply a graphical representation of steps. It shows steps in
sequential order and is widely used in presenting the flow of algorithms, workflow
or processes.
• Pseudocode is an artificial and informal language that helps programmers to
develop algorithms.
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A sample C programming language
#include<stdio.h>
int main()
{
int hours=5;
int rate=4;
int pay;
pay= hours*rate;
printf("%d", pay);
return 0;
}
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Algorithm
• Step 1: Start
• Step 2: Read hours, rate
• Step 3: Calculate pay=hours*rate
• Step 4: Print or display pay
• Step 5: Stop
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Flowchart and Pseudocode: Example
28-07-2022 15:08 5

C Keywords and Identifiers
• Character set
• A character set is a set of alphabets, letters and some special characters that are valid
in C language.
• Alphabets
• C accepts both lowercase and uppercase alphabets as variables and functions.
• Digits
• White space Characters
• Blank space, newline, horizontal tab, carriage return and form feed.
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Special Characters
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C Keywords
• Keywords are predefined, reserved words used in programming that have
special meanings to the compiler. Keywords are part of the syntax and they
cannot be used as an identifier. For example:
• int pay;
• Here, int is a keyword that indicates pay is a variable of type int (integer).
• As C is a case sensitive language, all keywords must be written in lowercase.
Here is a list of all keywords allowed in ANSI C.
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C Identifiers
• Identifier refers to name given to entities such as variables, functions,
structures etc.
• Identifiers must be unique. They are created to give a unique name to an
entity to identify it during the execution of the program. For example:
• int pay;
• Here pay is an identifier
• Also remember, identifier names must be different from keywords.
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Rules for naming identifiers
• A valid identifier can have letters (both uppercase and lowercase letters),
digits and underscores.
• The first letter of an identifier should be either a letter or an underscore.
• You cannot use keywords like int, while etc. as identifiers.
• There is no rule on how long an identifier can be. However, you may run
into problems in some compilers if the identifier is longer than 31 characters.
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C Variables, Constants and Literals
• Variables
• In programming, a variable is a container (storage area) to hold data.
• To indicate the storage area, each variable should be given a unique name (identifier).
Variable names are just the symbolic representation of a memory location.
• For example:
• int playerScore = 95;
• Here, playerScore is a variable of int type. Here, the variable is assigned an integer value
95.
• The value of a variable can be changed, hence the name variable.
• char ch = 'a';
• // some code
• ch = 'l';
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Rules for naming a variable
• A variable name can only have letters (both uppercase and lowercase letters),
digits and underscore.
• The first letter of a variable should be either a letter or an underscore.
• There is no rule on how long a variable name (identifier) can be. However,
you may run into problems in some compilers if the variable name is longer
than 31 characters.
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Strongly typed language
• C is a strongly typed language. This means that the variable type cannot be changed
once it is declared. For example:
• int number = 5; // integer variable
• number = 5.5; // error
• double number; // error
• Here, the type of number variable is int. You cannot assign a floating-point
(decimal) value 5.5 to this variable. Also, you cannot redefine the data type of the
variable to double. By the way, to store the decimal values in C, you need to declare
its type to either double or float.
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Literals
• Literals are data used for representing fixed values. They can be used directly
in the code. For example: 1, 2.5, 'c' etc.
• Here, 1, 2.5 and 'c' are literals. Why? You cannot assign different values to
these terms.
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Integers
• An integer is a numeric literal(associated with numbers) without any fractional or
exponential part. There are three types of integer literals in C programming:
• decimal (base 10)
• octal (base 8)
• hexadecimal (base 16)
• For example:
• Decimal: 0, -9, 22 etc
• Octal: 021, 077, 033 etc
• Hexadecimal: 0x7f, 0x2a, 0x521 etc
• In C programming, octal starts with a 0, and hexadecimal starts with a 0x
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Floating-point Literals
• A floating-point literal is a numeric literal that has either a fractional form or
an exponent form. For example:
• -2.0
• 0.0000234
• -0.22E-5
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Characters
• A character literal is created by enclosing a single character inside single
quotation marks. For example: 'a', 'm', 'F', '2', '}' etc.
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Escape Sequences
• Sometimes, it is necessary to use characters that cannot be typed or has
special meaning in C programming. For example: newline(enter), tab,
question mark etc.
• In order to use these characters, escape sequences are used.
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String Literals
• A string literal is a sequence of characters enclosed in double-quote marks.
For example:
• "good" //string constant
• "" //null string constant
• " " //string constant of six white space
• "x" //string constant having a single character.
• "Earth is roundn" //prints string with a newline
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Constants
• If you want to define a variable whose value cannot be changed, you can use
the const keyword. This will create a constant. For example,
• const double PI = 3.14;
• Notice, we have added keyword const.
• Here, PI is a symbolic constant; its value cannot be changed.
• const double PI = 3.14;
• PI = 2.9; //Error
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C Data Types
• In C programming, data types are declarations for variables. This determines
the type and size of data associated with variables. For example,
• int myVar;
• Here, myVar is a variable of int (integer) type. The size of int is 4 bytes.
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Basic types
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int
• Integers are whole numbers that can have both zero, positive and negative
values but no decimal values. For example, 0, -5, 10
• We can use int for declaring an integer variable.
• int id;
• Here, id is a variable of type integer.
• You can declare multiple variables at once in C programming. For example,
• int id, age;
• The size of int is usually 4 bytes (32 bits). And, it can take 232 distinct states
from -2147483648 to 2147483647.
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float and double
• float and double are used to hold real numbers.
• float salary;
• double price;
• In C, floating-point numbers can also be represented in exponential. For
example,
• float normalizationFactor = 22.442e2;
• What's the difference between float and double?
• The size of float (single precision float data type) is 4 bytes. And the size of
double (double precision float data type) is 8 bytes.
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char and void
• Keyword char is used for declaring character type variables. For example,
• char test = 'h';
• The size of the character variable is 1 byte.
• void is an incomplete type. It means "nothing" or "no type". You can think
of void as absent.
• For example, if a function is not returning anything, its return type should be
void.
• Note that, you cannot create variables of void type.
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short and long
• If you need to use a large number, you can use a type specifier long. Here's how:
• long a;
• long long b;
• long double c;
Here variables a and b can store integer values. And, c can store a floating-point number.
• If you are sure, only a small integer ([−32,767, +32,767] range) will be used, you can use
short.
• short d;
• You can always check the size of a variable using the sizeof() operator.
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signed and unsigned
• In C, signed and unsigned are type modifiers. You can alter the data storage of a
data type by using them. For example,
• unsigned int x;
• int y;
• Here, the variable x can hold only zero and positive values because we have used the
unsigned modifier.
• Considering the size of int is 4 bytes, variable y can hold values from -231 to 231-1,
whereas variable x can hold values from 0 to 232-1.
• Other data types defined in C programming are:
• bool Type
• Enumerated type
• Complex types
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Derived Data Types
• Data types that are derived from fundamental data types are derived types.
For example: arrays, pointers, function types, structures, etc.
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C Input Output (I/O)
• C Output
• In C programming, printf() is one of the main output function. The function
sends formatted output to the screen.
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Example 1: C Output
• #include <stdio.h>
• int main()
• {
• // Displays the string inside quotations
• printf("C Programming");
• return 0;
• }
• Output
• C Programming
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How does this program work?
• All valid C programs must contain the main() function. The code execution
begins from the start of the main() function.
• The printf() is a library function to send formatted output to the screen. The
function prints the string inside quotations.
• To use printf() in our program, we need to include stdio.h header file using
the #include<stdio.h> statement.
• The return 0; statement inside the main() function is the "Exit status" of the
program. It's optional.
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Example 2: Integer Output
• int main()
• {
• int testInteger = 5;
• printf("Number = %d", testInteger);
• return 0;
• }
• Output
Number = 5
• We use %d format specifier to print int types. Here, the %d inside the quotations
will be replaced by the value of testInteger.
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Example 3: float and double Output
• int main()
• {
• float number1 = 13.5;
• double number2 = 12.4;
• printf("number1 = %fn", number1);
• printf("number2 = %lf", number2);
• return 0;
• }
• Output
• number1 = 13.500000
• number2 = 12.400000
• To print float, we use %f format specifier. Similarly, we use %lf to print double values.
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Example 4: Print Characters
• int main()
• {
• char chr = 'a';
• printf("character = %c", chr);
• return 0;
• }
• Output
• character = a
• To print char, we use %c format specifier.
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C Input
• In C programming, scanf() is one of the commonly used function to take
input from the user.
• The scanf() function reads formatted input from the standard input such as
keyboards.
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Example 5: Integer Input/Output
• int main()
• {
• int testInteger;
• printf("Enter an integer: ");
• scanf("%d", &testInteger);
• printf("Number = %d",testInteger);
• return 0;
• }
• Output
• Enter an integer: 4
• Number = 4
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Example 5: Integer Input/Output
• Here, we have used %d format specifier inside the scanf() function to take
int input from the user. When the user enters an integer, it is stored in the
testInteger variable.
• Notice, that we have used &testInteger inside scanf(). It is because
&testInteger gets the address of testInteger, and the value entered by the
user is stored in that address.
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Example 6: Float and Double
Input/Output
#include <stdio.h>
int main()
{
float num1;
double num2;
printf("Enter a number: ");
scanf("%f", &num1);
printf("Enter another number: ");
scanf("%lf", &num2);
printf("num1 = %fn", num1);
printf("num2 = %lf", num2);
return 0;
}
• Output
• Enter a number: 12.523
• Enter another number: 10.2
• num1 = 12.523000
• num2 = 10.200000
• We use %f and %lf format specifier for float and double respectively.
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Example 7: C Character I/O
#include <stdio.h>
int main()
{
char chr;
printf("Enter a character: ");
scanf("%c",&chr);
printf("You entered %c.", chr);
return 0;
}
• Output
• Enter a character: g
• You entered g
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Example 7: C Character I/O
• When a character is entered by the user in the above program, the character
itself is not stored. Instead, an integer value (ASCII value) is stored.
• And when we display that value using %c text format, the entered character
is displayed. If we use %d to display the character, it's ASCII value is printed.
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Example 8: ASCII Value
#include <stdio.h>
int main()
{
char chr;
printf("Enter a character: ");
scanf("%c", &chr);
// When %c is used, a character is displayed
printf("You entered %c.n",chr);
// When %d is used, ASCII value is displayed
printf("ASCII value is %d.", chr);
return 0;
}
• Output
• Enter a character: g
• You entered g.
• ASCII value is 103.
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I/O Multiple Values
Here's how you can take multiple inputs from the user and display them.
#include <stdio.h>
int main()
{
int a;
float b;
printf("Enter integer and then a float: ");
// Taking multiple inputs
scanf("%d%f", &a, &b);
printf("You entered %d and %f", a, b);
return 0;
}
• Output
• Enter integer and then a float: -3
• 3.4
• You entered -3 and 3.400000
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Format Specifiers for I/O
• As you can see from the above examples, we use
• %d for int
• %f for float
• %lf for double
• %c for char
• Here's a list of commonly used C data types and their format specifiers.
28-07-2022 15:08 45

Data Type Format Specifier
int %d
char %c
float %f
double %lf
short int %hd
unsigned int %u
long int %li
long long int %lli
unsigned long int %lu
unsigned long long int %llu
signed char %c
unsigned char %c
long double %Lf
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C Programming Operators
• An operator is a symbol that operates on a value or a variable. For example:
+ is an operator to perform addition.
• C has a wide range of operators to perform various operations.
28-07-2022 15:08 47

C Arithmetic Operators
• An arithmetic operator performs mathematical operations such as addition,
subtraction, multiplication, division etc. on numerical values (constants and
variables).
Operator Meaning of Operator
+ addition or unary plus
- subtraction or unary minus
* multiplication
/ division
% remainder after division (modulo division)
28-07-2022 15:08 48

C Increment and Decrement Operators
• C programming has two operators increment ++ and decrement -- to change
the value of an operand (constant or variable) by 1.
• Increment ++ increases the value by 1 whereas decrement -- decreases the
value by 1. These two operators are unary operators, meaning they only
operate on a single operand.
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Example 2: Increment and Decrement
Operators
// Working of increment and decrement operators
#include <stdio.h>
int main()
{
int a = 10, b = 100;
float c = 10.5, d = 100.5;
printf("++a = %d n", ++a);
printf("--b = %d n", --b);
printf("++c = %f n", ++c);
printf("--d = %f n", --d);
return 0;
}
Output
++a = 11
--b = 99
++c = 11.500000
--d = 99.500000
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C Assignment Operators
• An assignment operator is used for assigning a value to a variable. The most
common assignment operator is =
Operator Example Same as
= a = b a = b
+= a += b a = a+b
-= a -= b a = a-b
*= a *= b a = a*b
/= a /= b a = a/b
%= a %= b a = a%b
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C Relational Operators
• A relational operator checks the relationship between two operands. If the
relation is true, it returns 1; if the relation is false, it returns value 0.
Operator Meaning of Operator Example
== Equal to 5 == 3 is evaluated to 0
> Greater than 5 > 3 is evaluated to 1
< Less than 5 < 3 is evaluated to 0
!= Not equal to 5 != 3 is evaluated to 1
>= Greater than or equal to 5 >= 3 is evaluated to 1
<= Less than or equal to 5 <= 3 is evaluated to 0
28-07-2022 15:08 52

Example 4: Relational Operators
// Working of relational operators
#include <stdio.h>
int main()
{
int a = 5, b = 5, c = 10;
printf("%d == %d is %d n", a, b, a == b);
printf("%d == %d is %d n", a, c, a == c);
printf("%d > %d is %d n", a, b, a > b);
printf("%d > %d is %d n", a, c, a > c);
printf("%d < %d is %d n", a, b, a < b);
printf("%d < %d is %d n", a, c, a < c);
printf("%d != %d is %d n", a, b, a != b);
printf("%d != %d is %d n", a, c, a != c);
printf("%d >= %d is %d n", a, b, a >= b);
printf("%d >= %d is %d n", a, c, a >= c);
printf("%d <= %d is %d n", a, b, a <= b);
printf("%d <= %d is %d n", a, c, a <= c);
return 0;
}
28-07-2022 15:08 53

Example 4: Relational Operators output
Output
5 == 5 is 1
5 == 10 is 0
5 > 5 is 0
5 > 10 is 0
5 < 5 is 0
5 < 10 is 1
5 != 5 is 0
5 != 10 is 1
5 >= 5 is 1
5 >= 10 is 0
5 <= 5 is 1
5 <= 10 is 1
28-07-2022 15:08 54

C Logical Operators
• An expression containing logical operator returns either 0 or 1 depending
upon whether expression results true or false.
Operator Meaning Example
&&
Logical AND. True only if all
operands are true
If c = 5 and d = 2 then,
expression ((c==5) && (d>5))
equals to 0.
||
Logical OR. True only if either
one operand is true
If c = 5 and d = 2 then,
expression ((c==5) || (d>5))
equals to 1.
!
Logical NOT. True only if the
operand is 0
If c = 5 then, expression !(c==5)
equals to 0. 28-07-2022 15:08 55

Example 5: Logical Operators
// Working of logical operators
#include <stdio.h>
int main()
{
int a = 5, b = 5, c = 10, result;
result = (a == b) && (c > b);
printf("(a == b) && (c > b) is %d n", result);
result = (a == b) && (c < b);
printf("(a == b) && (c < b) is %d n", result);
result = (a == b) || (c < b);
printf("(a == b) || (c < b) is %d n", result);
result = (a != b) || (c < b);
printf("(a != b) || (c < b) is %d n", result);
result = !(a != b);
printf("!(a != b) is %d n", result);
result = !(a == b);
printf("!(a == b) is %d n", result);
return 0;
}
28-07-2022 15:08 56

• Output
(a == b) && (c > b) is 1
(a == b) && (c < b) is 0
(a == b) || (c < b) is 1
(a != b) || (c < b) is 0
!(a != b) is 1
!(a == b) is 0
28-07-2022 15:08 57

C Bitwise Operators
• During computation, mathematical operations like: addition, subtraction,
multiplication, division, etc are converted to bit-level which makes processing
faster and saves power.
• Bitwise operators are used in C programming to perform bit-level
operations.
28-07-2022 15:08 58

C Bitwise Operators: Contd.
Operators Meaning of operators
& Bitwise AND
| Bitwise OR
^ Bitwise exclusive OR
~ Bitwise complement
<< Shift left
>> Shift right
28-07-2022 15:08 59

sizeof operator
• The sizeof operator
• The sizeof is a unary operator that returns the size of data (constants, variables,
array, structure, etc).
#include <stdio.h>
void main()
{
char a;
printf("Size of char=%lu bytesn",sizeof(a));
}
• Output
• Size of char = 4 bytes
28-07-2022 15:08 60

Conditional or Ternary Operator (?:)
Here, Expression1 is the condition to be evaluated. If the condition(Expression1) is True then
Expression2 will be executed and the result will be returned. Otherwise, if the
condition(Expression1) is false then Expression3 will be executed and the result will be returned.
28-07-2022 15:08 61

Example: Program to Store the greatest of the
two Number.
#include <stdio.h>
int main()
{
int a=2,b=3,c;
c=a>b?a:b;
printf("%d is greater ",c);
return 0;
}
• Output
• 3 is greater
28-07-2022 15:08 62

Errors in C
• Error is an illegal operation performed by the user which results in abnormal
working of the program.
• Programming errors often remain undetected until the program is compiled
or executed.
• Some of the errors inhibit the program from getting compiled or executed.
• Thus errors should be removed before compiling and executing.
28-07-2022 15:08 63

Syntax errors
• Errors that occur when you violate the rules of writing C syntax are known
as syntax errors.
• Most frequent syntax errors are:
• Missing Parenthesis (})
• Printing the value of variable without declaring it
• Missing semicolon
28-07-2022 15:08 64

Run-time Errors
• Errors which occur during program execution(run-time) after successful
compilation are called run-time errors
• One of the most common run-time error is division by zero also known as
Division error
28-07-2022 15:08 65

Linker Errors
• These error occurs when after compilation we link the different object files
with main’s object
• These are errors generated when the executable of the program cannot be
generated.
• This may be due to wrong function prototyping, incorrect header files.
• One of the most common linker error is writing Main() instead of main().
28-07-2022 15:08 66

Logical Errors
• On compilation and execution of a program, desired output is not obtained
when certain input values are given
• These types of errors which provide incorrect output but appears to be error
free are called logical errors
28-07-2022 15:08 67

Logical Errors : Example
int main()
{
int i = 0;
// logical error : a semicolon after loop
for(i = 0; i < 3; i++);
{
printf("loop ");
continue;
}
getchar();
return 0;
}
28-07-2022 15:08 68

Semantic errors
• This error occurs when the statements written in the program are not meaningful to
the compiler.
• Example:
// C program to illustrate
// semantic error
void main()
{
int a, b, c;
a + b = c; //semantic error
}
28-07-2022 15:08 69

Object Code
• Object code generally refers to the output, a compiled file, which is
produced when the Source Code is compiled with a C compiler.
• The object code file contains a sequence of machine-readable instructions
that is processed by the CPU in a computer.
28-07-2022 15:08 70

Executable code
• Executable (also called the Binary) is the output of a linker after it
processes the object code.
• A machine code file can be immediately executable (i.e., runnable as a
program), or it might require linking with other object code files (e.g.
libraries) to produce a complete executable program.
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Linker
• In computer science, a linker is a computer program that takes one or more
object files generated by a compiler and combines them into one, executable
program.
28-07-2022 15:08 72

Loader
• In computer systems a loader is the part of an operating system that is
responsible for loading programs and libraries.
28-07-2022 15:08 73

C programming

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