Loops

Sunday, 14 August 2016
  • c-language support two types of loops they are  

  • pretest loop(entry controlled loop)
          if expression  is true it execute body of the loop otherwise it termites body of the loop.

           example: while,for

 while loop:

  • while loop is a pretest loop it execute body of the loop 1 or more times until condition is true.
           syntax:         while(expression)
                              {
                                 body;
                                }
                               statement x;
/*program to generate positive integers */

#include<stdio.h>

#include<conio.h>

main()

{

int i=1;

clrscr();

while(i<=5)

{

Printf(“\n %d”,i);

i=i+1;
}
getch();
}
Output:
1
2
3
4
5

 For loop:

  • for loop is pre tested or entry tested loop i.e condition is tested at the begining of the loop.
syntax:           for(initialization;condition;increment/decrement);
                        {
                            body;
                          }
                          statement x;

     working of for loop

  • first it execute initialization then test the condition if it is true execute statements/body of for loop.
  • then execute increment/decrement and test the condition again if it is true.
  • when condition is false go out of loop and execute statements outside the loop.
/*program to generate even numbers*/

 #include<stdio.h>
#include<conio.h>
main()
{
int i,n;
clrscr();
print f(“enter n value”);
scanf(“%d”,&n);
for(i=2;i<=n;i=i+2)
{
Printf(“\n %d”,i);
}
getch();
}

Output:
Enter n value 10
2
4
6
8
10
  • post test loop(exit controlled loop)
               in post test loop it check the condition after execution of body of the loop if condition is true it        execute body of the loop.
                        example: do...while

do...while

  • do while loop is also called as exit controlled loop 
  • it execute the body of loop one or more times.
syntax:           do
                         { 
                         body;
                          }while(expression);
                         statement x;

/*program to print positive integers*/


#include<stdio.h>
#include<conio.h>
main()
{
int i=1;
clrscr();
do{
printf(“%d”,i);
i=i+1;
}while(i<10);
getch();
}
Output:
123456789

You can also refer
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