In
any programming language, loops are used to execute a set of statements
repeatedly until a particular condition is satisfied.
A
sequence of statements are executed until a specified condition is true. This
sequence of statements to be executed is kept inside the curly braces { } known
as the Loop body. After every
execution of 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.
There are 3 type of
Loops in C language:
1.
while loop
2.
for loop
3.
do-while loop
1. 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:
variable initialization;
while (condition)
{
statements;
variable increment or decrement;
}
Example: Program to print first 10
natural numbers:
#include<stdio.h>
#include<conio.h>
void main( )
{
int
x;
x=1;
while(x<=10)
{
printf("%d\t", x);
x++;
}
getch();
}
Output:
2. for loop:
for loop is used to
execute a set of statements repeatedly until a particular condition is
satisfied. We can say it an open ended loop. General format is:
for(initialization; condition ; increment/decrement)
{
statement-block;
}
In for loop we have exactly
two semicolons, one after initialization and second after condition. In this
loop we can have more than one initialization or increment/decrement, separated
using comma operator. for loop can have only one condition.
Above Example with for loop:
#include<stdio.h>
#include<conio.h>
void main( )
{
int
x;
for(x=1;
x<=10; x++)
{
printf("%d\t",x);
}
getch();
}
Output:
3. Nested for loop:
We can also have nested for loops, i.e one for loop inside another for loop. Basic syntax
is:
for (initialization; condition; increment/decrement)
{
for
(initialization; condition; increment/decrement)
{
statement;
}
}
Example : Program to print half
Pyramid of numbers:
#include<stdio.h>
#include<conio.h>
void main( )
{
int
i,j;
for(i=1;i<5;i++)
{
printf("\n");
for(j=i;j>0;j--)
{
printf("%d",j);
}
}
getch();
}
Output:
1
21
321
4321
54321
4. 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. General
format of do-while loop is:
do
{
....
.....
}
while(condition)
Example : Program to print first ten
multiple of 5:
#include<stdio.h>
#include<conio.h>
void main()
{
int
a,i;
a=5;
i=1;
do
{
printf("%d\t",a*i);
i++;
}while(i
<= 10);
getch();
}
Output:
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, that is called jumping out of loop. C language allows jumping from one
statement to another within a loop as well as jumping out of the 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.
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