C language unit-1

What is C?
• Language written by Brian Kernighan and
Dennis Ritchie
• C has been used as a general – purpose
language because of its popularity
• It was written to become first “portable”
language

Why use C?
• Mainly because it produces code that runs nearly as fast as code
written in assembly language. Some examples of the use of C might be:
• Operating Systems
• Language Compilers
• Assemblers
• Text Editors
• Print Spoolers
• Network Drivers
• Modern Programs
• Data Bases
• Language Interpreters
• Utilities
Mainly because of the portability that writing standard C programs can
offer

History
• 1960 : -
• ALGOL was found by International group of computer users.
• COBOL was found for commercial application usage.
• FORTRAN was found for scientific applications.
• In 1967: -
• Basic Combined Programming Language (BCPL)
• developed by Martin Richards at Cambridge University.
• a single language which can program all possible applications,
• In 1970: -
• a language called B was developed by Ken Thompson at AT & T’s Bell Labs.

History
• In 1972: -
• Dennis Ritchie at Bell Labs developed a language with some additional
features of BPCL and B called C.
• In 1978: -
• Publication of The C Programming Language by Kernighan & Ritchie caused a
revolution in the computing world.
• In 1983: -
• the American National Standards Institute (ANSI) established a committee to
provide a modern, comprehensive definition of C. The resulting definition, the
ANSI standard, or "ANSI C", was completed late 1988.

Why C Still Useful?
• C characteristics:
 Highly structured language
 Handle bit-level operations
 Machine independent language-highly portable
 Supports variety of data types and powerful set of operators
 Supports dynamic memory management by using concept of pointers
• C is used to develope:
 System software - Compilers, Editors, embedded systems
 data compression, graphics and computational geometry, utility programs
 databases, operating systems, device drivers, system level routines
 there are zillions of lines of C legacy code
 Also used in application programs

Programming languages
• Some understandable directly by computers
• Others require “translation” steps
• Various programming languages
• Machine language
• Assembly language
• High-level language
• Machine language
• Natural language of a particular computer
• Consists of strings of numbers(1s, 0s)
• Instruct computer to perform elementary
operations one at a time
• Machine dependent

• Assembly Language
• English like abbreviations
• Assemblers:
• Translators of programs
• Convert assembly language programs to machine language.
• E.g. add overtime to base pay and store result in gross pay
LOAD BASEPAY
ADD OVERPAY
STORE GROSSPAY

• High-level languages
• To speed up the programming process
• Single statements for accomplishing substantial tasks
• Compilers - convert high-level programs into machine
language
• E.g. add overtime to base pay and store result in gross pay
grossPay = basePay + overtimePay

Basics of C Environment
• C systems consist of 3 parts
• Environment
• Language
• C Standard Library
• Development environment has 6 phases
 Edit - Writing the source code by using some IDE or editor
 Pre-processor - Already available routines
 Compile - translates or converts source to object code for a
specific platform ie., source code -> object code
 Link - resolves external references and produces the executable
module
 Load – put the program into the memory
 Execute – runs the program

Phase 1 Editor Disk
Program edited in
Editor and stored
on disk
Phase 2 Preprocessor Disk
Preprocessor
program processes
the code
Phase 3 Compiler Disk
Creates object code
and stores on disk
Phase 4 Linker Disk
Links object code
with libraries and
stores on disk

Phase 5 Loader
Puts program in
memory
Primary memory
Phase 6 CPU
Takes each instruction
and executes it storing
new data values
Primary memory

Executing a C Program
Steps involved in execution are
• Creating the program
• Compiling the program
• Linking the program with functions that are needed from the
C library
• Executing the program

Executing a C Program
Edit
Program
Source
Code
Compile
Object
Code
Link Object
Code Executable
Library
Files

Basics Structure of C Program
Documentation section
Link section
Definition section
Global declaration section
main() function section
{
Declaration part
Executable part
}
Subprogram section
(user defined function)

Simple C Program
/* A first C Program*/
#include <stdio.h>
void main()
{
printf("Hello World n");
}

Simple C Program
• Line 1: #include <stdio.h>
• As part of compilation, the C compiler runs a program called
the C preprocessor. The preprocessor is able to add and
remove code from your source file.
• In this case, the directive #include tells the preprocessor to
include code from the file stdio.h.
• This file contains declarations for functions that the program
needs to use. A declaration for the print function is in this file.

Simple C Program
• Line 2: void main()
• This statement declares the main function.
• C program can contain many functions but must always have
one main function.
• A function is a self-contained module of code that can
accomplish some task.
• Functions are examined later.
• "void" specifies the return type of main. In this case, nothing is
returned to the operating system.

Simple C Program
• Line 3: {
• This opening bracket denotes the start of the
program.

Simple C Program
• Line 4: printf("Hello Worldn");
• printf is a function from a standard C library that is
used to print strings to the standard output, normally
your screen.
• The "n" is a special format modifier that tells the
printf to put a line feed at the end of the line.
• If there were another printf in this program, its string
would print on the next line.

Simple C Program
• Line 5: }
• This closing bracket denotes the end of the
program.

C Character Set
• Characters are the basic building blocks in C program,
equivalent to ‘letters’ in English language
• Characters can be used to form words, numbers and
expressions
• Characters in C are grouped into following categories
• Letters ex:a…z,A…Z
• Digits ex:0…9
• Special characters ex:,,&,@,_,+,-,…..
• White spaces ex:blank space
horizontal tab
new line…….

C Tokens
• In a passage of text, individual words and punctuation marks
are called tokens
• In a C source program, the basic element recognized by the
compiler is the "token."
• C Tokens are
 Keywords - int, float, while
 Identifiers - sum, main
 Constants - 100, -55.5
 Strings - “ABC”, “Hello”
 Operators - +, -, *, /, ++
 Special symbols - {, },[, ]

Keywords
• All keywords are reserved words have fixed meanings and
these meanings cannot be changed
• Have special meaning to the compiler, cannot be used as
identifiers in our program.
• Keywords serve as basic building blocks for program
statement
• Keywords must be written in lowercase
• Displayed in BLUE color in MS Visual C++

Some Keywords
Keywords
auto double int struct
break else long switch
case enum register typedef
char extern return union
const float short unsigned
continue for signed void
default goto sizeof volatile
do if static while

Identifiers
• Refer to the names of variables, functions and arrays
• User defined names and consist of a letters and
digits, with a letter as a first character
Rules for Identifiers
• First character must be an alphabet
• Must consist of only letters, digits and underscore
• Only first 32 characters are significant
• Cannot use a keyword
• Must not contain white space
• Case sensitive-Identifier Sub differ from sub

Identifiers
Examples of legal identifier:
Student_age, Item10, counter, number_of_character
Examples of illegal identifier
Student age (embedded blank)
continue (continue is a reserved word)
10thItem (the first character is a digit)
Principal+interest (contain operator character +)

Recommendations for Constructing Identifiers
1. Avoid excessively short and cryptic names such as x or wt. Instead,
use a more readable and descriptive names such as student_major
and down_payment.
2. Use underscores or capital letters to separate words in identifiers
that consist of two or more words. Example, student_major or
studentMajor are much easier to read than studentmajor.

Constants
• Constants refers to fixed values that do not change during the
execution a program
Types of Constants
Numeric Constants
 Integer Constants - 234, 045, 0x2A, 0X3B
 Real Constants - 2.345, 0.64e-2
Character Constants
 Single Character Constants ‘5’, ‘A’
 String Constants “Hello”

Integer Constant
Positive or negative whole numbers with no fractional part
Optional + or – sign before the digit.
It can be decimal (base 10), octal (base 8) or hexadecimal (base 16)
Hexadecimal is very useful when dealing with binary numbers
Example:
const int MAX_NUM = 10;
const int MIN_NUM = -90;
const int Hexadecimal_Number = 0xf87;

Rules for Decimal Integer Constant
1. Decimal integer constants must begin with a nonzero decimal digit, the
only exception being 0, and can contain decimal digital values of 0 through
9. An integer that begins with 0 is considered an octal constant
2. If the sign is missing in an integer constant, the computer assumes a
positive value.
3. Commas are not allowed in integer constants. Therefore, 1,500 is illegal; it
should be 1500.
Example of legal integer constants are –15, 0, +250 and 7550
Example of illegal constants
0179 is illegal since the first digit is zero
1F8 is illegal since it contains letter ‘F’
1,700 is illegal since it contains comma

Floating Point Constant
• Positive or negative decimal numbers with an integer part(optional), a
decimal point, and a fractional part (optional)
Example 2.0, 2., 0.2, .2, 0., 0.0, .0
• It can be written in conventional or scientific way
• 20.35 is equivalent to 0.2035E+2 (0.2035 x 102 )
• 0.0023 is equivalent to 0.23e-2 (0.23 x 10-2)
• E or e stand for “exponent”
• In scientific notation, the decimal point may be omitted.
Example: -8.0 can rewritten as -8e0

Floating Point Constant
• C support 3 type of Floating-point: float (4 bytes), double (8 bytes), long
double (16 bytes)
• By default, a constant is assumed of type double
• Suffix f(F) or l(L) is used to specify float and long double respectively
Example:
const float balance = 0.125f;
const float interest = 6.8e-2F
const long double PI = 3.1412L;
const long double planet_distance = 2.1632E+30l

• A character enclosed in a single quotation
mark
• Example:
• const char letter = ‘n’;
• const char number = ‘1’;
• printf(“%c”, ‘S’);
• Output would be: S
How to write a single quotation mark?
‘’’ is ambiguous, so escape character – back slash
Example:
‘’’
Character Constants

String Literals
• A sequence of any number of characters surrounded by
double quotation marks.
• Example:
• “Human Revolution”
• How to write special double quotation mark?
• “”” is ambiguous, so use escape character
• Example: printf(“He shouted, “Run!””);
output: He shouted, “Run!”
- The escape character along with any character that follow it is
called Escape Sequence

Backslash Character Constants
Escape
Sequence
Name Meaning
a Alert Sounds a beep
b Back space Backs up 1 character
f Form feed Starts a new screen of page
n New line Moves to beginning of next line
r Carriage return Moves to beginning of current line
t Horizontal tab Moves to next tab position
v Vertical tab Moves down a fixed amount
Back slash Prints a back slash
’ Single quotation Prints a single quotation
” Double quotation Prints a double quotation
? Question mark Prints a question mark

Backslash Character Example
Program
#include<stdio.h>
void main()
{
printf("nabc");
printf("rdef");
printf("bghin");
printf("HaitHello");
}
Output
deghi
Hai Hello

Variables
• A variable is a data name used for storing a data value
• The value may be changed during program execution
Rules for defining variables
• Must begin with a character
• Should not be a C keyword
• May be combination of lower and upper characters
• Should not start with a digit
• Maximum characters upto 31 characters
Example
Sum, avg_wt, item

Declaration of Variables
• Syntax for declaring a variable is as follows
data-type v1,v2,….vn;
Example
int i,j,sum;
float avg;
double ratio;
unsigned int fact;

DATATYPE
• Datatype is the most important attributes of an identifier. It
detemines the possible values.
• Classification of Datatypes
-Basic Datatypes
-Derived datatypes
-User-defined datatypes
Basic/Primitive Datatypes:
Character (char)
Integer (int)
Single-precision floating point (float)
Double-precision floating point (double)
No value available (void)
Derived Datatypes:
Array type (char[], int[])
Pointer type (char*, int*)
Functiontype (int(int,int), float(int))

• User-defined datatypes
It provides flexibility to the user to create new datatypes.
Newly created called User-defined datatypes.
Structure
Union
Enumeration
Syntax:
data_type variable_name
Example:
int age;
char ch;
float avg;
int a,b,c;

Data Types
Initializing Variables
• Variables declared can be assigned or initialized using an assignment
operator ‘=‘
Syntax:
variable_name=constant;
or
data_type variable_name=constant;
Example:
int age; char ch=‘A’;
age=10; float avg=10.5;

Data Types in C
Type Keyword
Byte
s
Range
character char 1 -guatda.com/cmx.p128...127
integer int 2 -32768...32767
short integer short 2 -32768...32767
long integer long 4 -2,147,483,648...2,147,438,647
long long
integer
long long 8
-9223372036854775808 …
9223372036854775807
unsigned
character
unsigned char 1 0...255
unsigned
integer
unsigned int 2 0...4,294,967,295
unsigned short
integer
unsigned short 2 0...65535
unsigned long
integer
unsigned long 4 0...4,294,967,295
single-precision float 4 1.2E-guatda.com/cmx.p38...3.4E38
double-precision
double 8 2.2E-guatda.com/cmx.p308...1.8E308

Expressions
• Operands
It specifies an entity on which an operation is
to be performed. It may be a variable name, a
constant, a function call or a macro name
eg: a=printf(“Hello”)+2
• Operators
It specifies the operation to be applied to its
operands.

Simple Expression and Compound
Expression
• An Expression has only one operator called
Simple expression
eg: a+2
• An Expression has more than one operator
called Compound Expression.
eg: b=2+3*5

Properties Of Operators
• Precedence
• Associativity
Precedence:
• Priority allotted to the operator
• Each operator in C has a precedence associated with it.
• In compound expression, if the operator involved
different precedence, the operator of highest precedence
operates first.
Ex: 8+9*2-10
=8+18-10
=26-10
=16

Associativity:
• Expression having operators with equal precedence
• associativity property decides which operation is
performed first
• In compound expression, when several operators of
the same precedence appear together, the operators are
evaluated according to their associativity.
Types: Left to Right Right to left
12*4/8%2 x=8+5%2
= 48/8%2 =8+1
= 6%2 =9
= 0

• Operators has same precedence- same
associativity
• If operators are left-to-right, applied in a
left-to-right order
• If operators are right-to-left, applied in a
right-to-left order
• Multiplication and division operators are
left-to-right associative

Operators
• An operator is a symbol that tells the computer to perform
certain mathematical or logical manipulations
Classification of Operators:
Number of operands on which an operator operates
The role of an operator
Classification based on Number of operands
• Unary- it operates on only one operand
Eg: &, sizeof operator, !, ~, ++, --
• Binary – it operates on two operands
eg: *, /, <<, ==,&&, &
• Ternary- it operates on three operands
eg: ?:

Classification based on Role of
Operator
Arithmetic Operators +, -, *, /, %
Relational Operators <, <=, >, >=, ==, !=
Logical Operators &&, ||, !
Assignment Operators =
Increment and Decrement Operators ++,--
Conditional Operators ?=
Bitwise Operators &,|, ^, <<, >>
Special Operators ,, sizeof, &, * ., ->

Arithmetic Operators
C Operation Algebraic C
Addition (+) f + 7 f + 7
Subtraction (-) p – c p – c
Multiplication (*) bm b * c
Division (/) x / y x / y
Modulus (%) r mod s r % s

Arithmetic Operators Example
Program
d = x / y;
#include <stdio.h>
printf(“d = %dn",d);
#include <conio.h>
r = x % y;
void main()
printf("r = %dn",r);
{
}
int x,y, a,s,m,d,r;
clrscr();
Output
printf(“Enter two numbers:”);
Enter two numbers:10 20
scanf(“%d%d”,&x,&y);
a = x + y;
a = 30
printf(“a = %dn",a);
s = -10
s = x - y;
m = 200
printf(“s = %dn",s);
d = 0
m = x * y;
r = 10
printf(“m = %dn",m);

Binary Arithmetic operators
• It is used in 3 different modes
Integer mode

Relational Operators
• Greater than >
• Less than <
• Greater than or equal to >=
• Less than or equal to <=
• Equal to ==
• Not equal to !=
Condition true return 1
Condition false return 0

Relational Operators Example
Program
#include<stdio.h>
#include<conio.h>
void main()
{
int x,y,r;
clrscr();
printf(“Enter 2 nos. x & y:”);
scanf(“%d%d”,&x,&y);
r=(x==y);
printf("%dn",r);
r=(x!=y);
printf("%dn",r);
r=(x>y);
printf("%dn",r);
r=(x>=y);
printf("%dn",r);
r=(x<y);
printf("%dn",r);
r=(x<=y);
printf("%dn",r);
}
Output
Enter 2 nos. x & y: 10 20
0
1
0
0
1
1

Logical Operators
Operator Example Meaning
&& (Logical AND)
(Condition1) &&
(Condition2)
Both conditions should
satisfy to proceed
|| (Logical OR)
(Condition1) ||
(Condition2)
Either one condition
satisfied proceed to
next operation
! (Logical NOT) !(Condition1)
The condition not
satisfied proceed to
next operation

Logical Operators
Example
if ((x>20) && (x<100)) printf("x is inside open interval
20-
100");
if ((x<5) || (x>20)) printf("x is not inside closed interval 5-20");
if (!(x>20)) printf("x is smaller or equal to 20");

Logical Operators Example
//Greatest of 3 numbers using
logical operators
#include<stdio.h>
#include<conio.h>
void main()
{
int x,y,z;
clrscr();
printf(“Enter 3 nos. x ,y,z:”);
scanf(“%d%d%d”,&x,&y,&z);
if((x>y)&&(x>z))
printf(“x is greatest”);
if((y>x)&&(y>z))
printf(“y is greatest”);
if((z>x)&&(z>y))
printf(“z is greatest”);
}
Output
Enter 3 nos. x ,y,z: 40 20 30
x is greatest
Enter 3 nos. x ,y,z: 10 40 30
y is greatest
Enter 3 nos. x ,y,z: 10 20 30
z is greatest

Assignment operators
= 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

Increment/Decrement
operators
++ a++
First does the operation
and increments the value
+ + ++a
First Increments the value
and does the operation
-- a--
First does the operation
and decrements the
value
-- --a
First decrements the
value and does the
operation

Increment/Decrement
operators
Program
void main()
{
int c;
c = 5;
printf(“%dn”, c);
printf(“%dn”, c++);
printf(“%dnn”, c);
c = 5;
printf(“%dn”, ++c);
}
Output
5
5
6
5
6
6
c=10
x=c++ + ++c;
x=? C=?

Conditional Operator
Conditional Operator (?:) is ternary operator (demands 3 operands),
and is used in certain situations, replacing if-else condition phrases.
Conditional operator’s syntax is:
condition?expression1:expression2;
If condition is true, expression1 is executed.
If condition is false, expression2 is executed.
Example:
int a, b, c;
...
c = a > b ? a : b; // if a>b "execute" a, else b and
assign the value to
c

Bitwise Operators
Operator Meaning
& Bitwise AND
| Bitwise OR
^ Bitwise XOR
~ One’s Complement
<< Left Shift
>> Right Shift

Bitwise Operators Example
Let A=0x56 and B=0x32
A & B ( Bitwise AND )
0 1 0 1 0 1 1 0
0 0 1 1 0 0 1 0
---------------------
0 0 0 1 0 0 1 0
---------------------
A ^ B ( Bitwise XOR )
0 1 0 1 0 1 1 0
0 0 1 1 0 0 1 0
---------------------
0 1 1 0 0 10 0
---------------------
A | B ( Bitwise OR )
0 1 0 1 0 1 1 0
0 0 1 1 0 0 1 0
---------------------
0 1 1 1 0 1 1 0
---------------------
~ A ( Complement )
0 1 0 1 0 1 1 0
---------------------
1 0 1 0 1 0 0 1
---------------------

Let A=0x56
A << 2 ( Left Shift )
0 1 0 1 0 1 1 0 << 2  0 1 0 1 0 1 1 0 0 0 ( 0x158 )
A >> 2 ( Right Shift )
0 1 0 1 0 1 1 0 >> 1  0 1 0 1 0 1 1 ( 0x2B)
NOTE:
For multiply given number by two, left shifted by one time, i.e., a<<1
For divide given number by two, right shifted by one time, i.e., a>>1

Write a program to shift inputed data by three bits left and right
Program
void main()
{
int x,y;
clrscr();
printf(“Enter value of x:”);
scanf(“%d”,&x);
y=x<<3;
printf(“Left shifted data=%d”,y);
printf(“Right shifted data=%d”,x>>3);
}
Output: Enter value of x:16
Left shifted data=128
Right shifted data=2

Special Operators
• C supports some special operators such as comma operator, size of
operator, pointer operators (& and *) and member selection
operators (. and ->).
• The size of and the comma operators are discussed here. The
remaining operators will see in pointer chapter
Comma Operator
• The comma operator can be used to link related expressions
together. A comma-linked list of expressions are evaluated left to
right and value of right most expression is the value of the combined
expression.
Example
value = (x = 10, y = 5, x + y);
 for (n=1, m=10, n <=m; n++,m++)
 t = x, x = y, y = t;

Special Operators
Sizeof Operator
• The operator sizeof gives the size of the data type or variable in
terms of bytes occupied in the memory. The operand may be a
variable, a constant or a data type qualifier.
• The size of operator is normally used to determine the lengths of
arrays and structures when their sizes are not known to the
programmer. It is also used to allocate memory space dynamically to
variables during the execution of the program.
Example
int sum;
m = sizeof(sum);  2
n = sizeof(long int);  4
k = sizeof(235L);  4

Expressions
Arithmetic Expressions
• An expression is a combination of variables constants and operators
written according to the syntax of C language.
Algebraic
Expression
C Expression
a x b – c a * b – c
(m + n) (x + y) (m + n) * (x + y)
3x2 +2x + 1 3*x*x+2*x+1

Expressions
Evaluation of Expressions
• Expressions are evaluated using an assignment statement of the
form
Variable = expression;
Variable is any valid C variable name.
The expression is evaluated first and then replaces the
previous value of the variable on the left hand side.
All variables used in the expression must be assigned values
before evaluation is attempted.
Example
x = a * b – c
y = b / c * a
z = a – b / c + d;

Decision Making - Branching
• Decision making statements are used to skip or to execute a group of
statements based on the result of some condition.
• The decision making statements are,
− simple if statement
− if…else statement
− nested if
− else … if ladder
− switch statement
− goto
• These statements are also called branching statements

Simple if statement
Syntax:
if(condition)
{
Statements;
}
if(condition)
Statements;
False
True (Bypass)

Simple if - Example
# include <stdio.h>
void main ()
{
int number;
printf("Type a number:");
scanf("%d",&number);
if (number < 0)
number = -number;
printf ("The absolute value is %d",number);
}
Output
Type a number -50
The absolute value is 50

if - else statement
Syntax:
if(condition)
{
True block statements;
}
else
{
False block statements;
}
if(condi
tion)
True Block
Statement
False
True
False Block
Statements

if – else Example
# include <stdio.h>
void main ()
{
int num;
printf ("Type a number:");
scanf ("%d", &num);
if (number < 0)
printf(“The number is negative”);
else
printf(“The number is positive”);
}
Output
Type a number 50
The number is positive

if – else Example
#include<stdio.h>
void main()
{
Int num;
printf ("Enter a number:");
scanf ("%d",&num);
if (num%2==0)
Output
Enter a number 125
The number is ODD
printf ("The number is
EVEN.n");
else
printf ("The number is ODD.n");
}

Nested if Statement
• if statement may itself can contain another if statement is known as nested if
statement.
Syntax:
if(condition1)
{
if(condition2)
{
True block statement of condition1 & 2;
}
else
{
False block statement of condition2;
}
}
else
{
False block statements of condition1;
}

Nested if Statement
condition1
True Block Statements of
condition 1 & 2;
False
True
False Block Statements of
condition 1;
if(condition2)
True
False
False Block Statements of
condition 2;

Nested if Example
# include <stdio.h>
void main()
{
int n1,n2,n3,big;
printf (“Enter 3 numbers:");
scanf ("%d %d %d", &n1,&n2,&n3);
if (n1 > n2)
{
if(n1 > n3)
big = n1;
else
big = n3;
}
if(n2 > n3)
big = n2;
else
big = n3;
printf(“The largest number is: %d”,big);
}
Output
Enter 3 numbers:10 25 20
The largest number is: 25

Else - if Ladder Statement
Syntax
if (condition1)
statement block 1;
else if (condition2)
statement block 2;
else if (condition3)
statement block 3;
:
:
else if (condition)
statement block n;
else
default statement;

Else - if Ladder Statement
If(condition1)
Default Statements;
True
False
Statements1;
Else if(condition2)
True
Statements2;
False
Else if(condition3)
Statements3;
False
True

Else - if Ladder Example
#include <stdio.h>
void main ()
{
int mark;
printf ("Enter mark:");
scanf ("%d", &mark);
if (mark <= 100 && mark >= 70)
printf ("n Distinction");
else if (mark >= 60)
printf("n First class");
else if (mark >= 50)
printf ("n Second class");
else
printf ("Fail");
}
Output
Enter mark: 75
Distinction

Switch Statement
Syntax
switch ( expression )
{
case value1: program statement;
......
break;
case value2: program statement;
.......
break;
…….
…….
case valuen: program statement;
.......
break;
default: program statement;
.......
break;
}

Switch Statement
Switch (Expression)
Case 1 Statements
Case 2 Statements
Case 3 Statements
Case 4 Statements

Switch Statement Example
#include <stdio.h>
void main ()
{
int num1, num2, result;
char operator;
printf ("Enter two numbers:");
scanf ("%d %d", &num1, &num2);
printf ("Enter an operator:");
scanf ("%c", &operator);
switch (operator)
{
case '+':
result = num1 + num2;
break;
case '-':
result = num1 - num2;
break;
case '*':
result = num1 * num2;
break;
case '/':
if (num2 != 0)
result = num1 / num2;
break;
default:
printf ("n unknown operator");
break;
}
printf (“Result=%d", result);
}
Output
Enter two numbers:10 20
Enter an operator:+
Result=30

Switch Statement Example
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char st[100];
int i,count=0;
clrscr();
printf("Enter line of text:");
gets(st);
for(i=0;st[i]!='0';i++)
{
switch(st[i])
{
case 'a': count++;
break;
case 'e': count++;
break;
case 'i': count++;
break;
case 'o': count++;
break;
case 'u': count++;
break;
}
}
printf("n Number of vowels: %d",count);
getch();
}
Output
Enter line of text: Hello World
Number of vowels: 3

goto statement
•The goto statement used to transfer the program control unconditionally from
one statement to another statement.
•The general usage is as follows:
goto label; Label:
………… …………
.............. …………
………… …………
………… …………
Label: Statement; goto label;
…………
•The goto requires a label in order to identify the place where the branch is to
be made.
•A label is a valid variable name followed by a colon.

goto statement example
#include <stdio.h>
void main ()
{
int n, sum = 0, i = 0;
printf ("Enter a number:");
scanf ("%d", &n);
inc: i++;
sum += i;
if (i < n)
goto inc;
printf ("n 1+2+3+…+%d = %d",n,sum)
}
Output
Enter a number:5
1+2+3+…+5=15

Looping statements
• The test may be either to determine whether the i has repeated the
specified number of times or to determine whether the particular
condition has been met.
• Type of Looping Statements are
• while statement
• do-while statement
• for statement

while statement
Syntax
while (test condition)
{
body of the loop;
}
While
(test
condition)
Body of the i;
False
True

while statement example
#include<stdio.h>
void main()
{
int n,x,sum=0;
printf("Enter a number: ");
scanf("%d",&n);
while(n>0)
{
x=n%10;
sum=sum+x;
n=n/10;
}
printf("Sum of digits of a number=%d",sum);
}
Output
Enter a number: 275
Sum of digits of a number=14

while statement example
#include<stdio.h>
void main()
{
int num,r,sum=0,temp;
printf("Enter a number: ");
scanf("%d",&num);
temp=num;
while(num!=0)
{
r=num%10;
sum=sum+(r*r*r);
num=num/10;
}
if(sum==temp)
printf("%d is an Armstrong number“
,temp);
else
printf("%d is not an Armstrong number“
,temp);
}
Output
Enter a number: 275
275 is an Armstrong number
Enter a number: 153
153 is an Armstrong number

do..while statement
• Since the body of the i is executed first and then the i condition is
checked we can be assured that the body of the i is executed at least
once.
Syntax
do
{
body of the loop;
}
while (test condition);

do..while statement
Body of the loop
While
(test
condition)
False
True
do

do..while statement example
#include<stdio.h>
void main()
{
int num=0, rev_num=0;
printf(“Enter the number:”);
scanf(“%d”,&num);
do
{
ld=num%10;
rev_num=rev_num*10+ld;
num=num/10;
} while(num>0);
printf(“nReversed number is %d”,rev_num);
}
Output
Enter the number:275
Reversed number is 572

while and do..while comparison
While Do…while
1) Syntax:
while(condition)
{
Body of the loop
}
1) Syntax:
do
{
Body of the loop
}while(condition);
2) This is decision making and
looping statement
2) This is also -decision making
and looping statement
3) This is the top tested loop 3) This is the bottom tested loop
4)Loop will not be executed if the
condition is false in first check
4) Loop will be executed atleast
once even though the condition is
false in first check

for statement
■ The for loop is most commonly and popularly used looping statement in C. The
for loop allows us to specify three things about the loop control variable i in a
single line. They are,
■ Initializing the value for the i
■ Condition in the i counter to determine whether the loop should continue or
not
■ Incrementing or decrementing the value of i counter each time the program
segment has been executed.
Syntax
for(initialization; test condition;increment/decrement)
{
body of the loop;
}

for statement
Initialization;
test condition
False
Increment/Decrement;
Body of the loop
True

for statement example
// Number 1 to 10 divisible by 2 but not
divisible by 3 and 5
#include<stdio.h>
void main()
{
int i;
for(i=1;i<=10;i++)
{
if(i%2==0&&i%3!=0&&i%5!=0)
printf("%dn",i);
}
}
Output
2
4
8

for statement example
//12+22+32+…. n2
#include<stdio.h> //<math.h>
void main()
{
int n, i,sum=0;
printf(“Enter the number:”);
scanf(“%d”, &n);
for(i=1;i <= n;i++)
{
sum = sum + i*i; //pow(i,2)
}
printf(“Sum of series=%d”,sum);
}
Output
Enter the number:5
Sum of series=55

break statement
■ Sometimes while executing a loop it becomes desirable to skip a part of
the loop or quit the loop as soon as certain condition occurs.
■ For example consider searching a particular number in a set of 100
numbers. As soon as the search number is found it is desirable to
terminate the loop.
■ C language permits a jump from one statement to another within a loop
as well as to jump out of the loop.
■ The break statement allows us to accomplish this task. A break statement
provides an early exit from for, while, do and switch constructs.
■ A break causes the innermost enclosing loop or switch to be exited
immediately.

break statement
#include<stdio.h>
void main()
{
int mark, i=0,sum=0;
float avg;
printf(“Enter the marks, -1 to end:”);
while(1)
{
scanf(“%d”, &mark);
if(mark == -1)
break;
sum+=mark;
i++;
}
avg=(float)sum/i;
printf(“nThe average marks is: %f”, avg);
}
Output
Enter the marks, -1 to end:
55
22
11
66
-1
The average marks is:38.500000

continue statement
■During loop operations it may be necessary to skip
a part of the body of the loop under certain
conditions.
■Like the break statement C supports similar
statement called continue statement.
■The continue statement causes the loop to be
continued with the next iteration after skipping
any statement in between.

continue statement
#include < stdio.h >
void main()
{
int i, num, sum=0;
printf(“Enter the integer:”);
for (i = 0; i < 5; i++)
{
Output
Enter the integer:11 22 33 -1
You have entered a negative number
44
Sum of positive numbers entered =110
scanf(“%d”, &num);
if(num < 0)
{
printf(“You have entered a negative numbern”);
continue;
}
sum+=num;
}
printf(“Sum of positive numbers entered = %d”,sum);
}

break and continue comparison
Break Continue
1) Syntax:
break;
1) Syntax:
continue;
2) Takes the control to outside of
the loop
2) Takes the control to beginning
of the loop
3) It is used in switch statement 3) It is not used in switch
statement
4) Example:
for(i=0;i<n;i++)
{
if(i==3)
break;
}
4) Example:
for(i=0;i<n;i++)
{
if(i==3)
continue;
}

Input and Output Functions
Input and Output Functions
Unformatted
Functions
Formatted Functions
scanf()
printf()
getch()
getche()
getchar()
gets()
putch()
putchar()
puts()

Formatted Functions
Formatted Input:
• Input data is arranged in a particular format
• I/P values are taken by using scanf function
• Syntax:
• scanf(“control string”,arg1,arg2…argn) ;
control string - includes format specifications and optional number
specifying field width and the conversion character %
arg1,arg2,… - address of locations where the data are stored
 Example: scanf(“%3d%2d”,&a,&b);

An Example Program
# include<stdio.h>
#include<conio.h>
void main()
{
int num1, num2;
clrscr();
printf (“Enter two values:”) ;
scanf(“%3d%4d”, &num1, &num2);
printf (“nThe Entered Values are:%d %d”, num1, num2) ;
getch();
}
Output 1:
Enter two values: 1342 2422
The Entered Values are: 134 2
Output 2:
Enter two values: 134 2422
The Entered Values are: 134 2422

An Example Program
# include<stdio.h>
#include<conio.h>
void main ( )
{
float n1, n2, n3;
clrscr();
printf (“Enter three values:”) ;
scanf(“%f%f%f”, &n1,&n2,&n3);
printf (“nThe Entered Values are:%ft%ft%f”, n1, n2, n3) ;
getch();
}
Output:
Enter three values: 123.44 4.7 678
The Entered Values are:123.440000 4.700000 678.000000

An Example Program
#include <stdio.h>
#include <conio.h>
void main()
{
float c, f;
clrscr();
printf("Enter temp in Centigrade: ");
scanf("%f",&c);
f = ( 1.8 * c ) + 32;
printf("Temp in Fahrenheit: %0.2f",f);
getch();
}
Output:
Enter temp in Centigrade: 95.6
Temp in Fahrenheit: 204.08

An Example Program
# include<stdio.h>
#include<conio.h>
void main ( )
{
char s1[10],s2[10];
clrscr();
printf (“Enter two strings:”) ;
scanf(“%3s%2s”,s1,s2);
printf (“nThe Entered Values are:%st%s”,s1,s2) ;
getch();
}
Output:
Enter two strings : hello world
The Entered Values are:hel lo

Formatted Functions
Formatted Output:
• printf statement displays the information required to user
with specified format
• Syntax:
printf(“control string”,arg1,arg2…argn) ;
control string - field format which includes format
specifications and optional number specifying field width and
the conversion character %, blanks, tabs and newline.
arg1,arg2,… - name of the variables
Example: printf(“%dt%fn”,sum1,sum2);

Format for various output
Flag output justification
+ (right justification) - (left justification)
Width Specifier minimum field width for an output value
TYPE FORMAT EXPLANATION
Integer %wd w-width
Float %w.cf w-width
c-no. of digits after decimal point
String %w.cs w-width of total characters
c-no. of characters to display

Example
• INTEGER
printf(“%d”,12345); 12345
printf(“%3d”,12345); 12345
printf(“%7d”,12345); 12345
printf(“%-7d”,12345); 12345
• FLOAT
printf(“%f”,123.45); 123.450000
printf(“%4.2f”,123.45); 123.45
printf(“%9.3d”,12345); 123.450
• STRING
printf(“%s”,”Hello World”); Hello World
printf(“%6.2s”,”Hello World”); He
printf(“%1.2s”,”Hello World”); He

Input / Output functions
#include<stdio.h>
void main()
{
int i;
float f;
char c;
double d;
printf("Enter value for i,f,c,d:");
scanf("%d %f %c %lf",&i,&f,&c,&d);
printf(“i=%dnf=%fnc=%cnd=%lf",i,f,c,d);
}
Output
Enter value for i,f,c,d: 10 2.3 A 5.6
i=10
f=2.300000
c=A
D=5.600000

Formatted & unformatted I/O
Fundamental
Data Type
Data Type
Conversion Symbol+Format
Specifier
Integer short integer %d or %i
short unsigned %u
long signed %ld
long unsigned %lu
unsigned hexadecimal %X or %x
unsigned octal %o
Real float %f or %g
double %lf
Character character %c
string %s

Unformatted Functions
Unformatted Input
getch() & getche()
 read a alphanumeric characters from the standard input
device such as the keyboard
 The character entered is not displayed by getch() function

Example : getch() & getche()
# include<stdio.h>
#include<conio.h>
void main ( )
{
clrscr();
printf (“Enter two alphabets:”) ;
getche();
getch();
}
Output:Enter two alphabets:A

getchar()
• read a character type data from the standard input device
such as the keyboard
• Reads one character at a time till user press the enter key

Example : getchar()
# include<stdio.h>
#include<conio.h>
void main ( )
{
char c;
clrscr();
printf (“Enter a character:”) ;
c=getchar();
printf(“c=%c”,c);
getch();
}
Output: Enter a character :A
c=A

gets()
• read a string from the standard input device such as the
keyboard until user press the enter key

Example : gets()
# include<stdio.h>
#include<conio.h>
void main ( )
{
char str[10];
clrscr();
printf (“Enter a string:”) ;
gets(str);
printf(“String=%s”,str);
getch();
}
Output: Enter a string :Hello
String=Hello

putch() & putchar()
• Prints any alphanumeric character taken by the standard
input device such as the keyboard
Example:
char ch=‘X’;
putch(ch); or putchar(ch);
Output: X

puts()
• prints the string or character array

Example : puts()
# include<stdio.h>
#include<conio.h>
void main ( )
{
char str[10];
clrscr();
printf (“Enter a string:”) ;
gets(str);
printf (“Entered string:”) ;
puts(str);
getch();
}
Output: Enter a string :Hello
Entered string:Hello

C language unit-1

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