Saturday, 22 December 2018

loop statements

  1. while loop (or) while statement :
The while loop is an entry control loop. In this, first condition is checked and if it true then body of the loop is executed, It will execute again and again till the condition is false. The syntax is:
             while(condition)
             {
                  body of the loop(statements);
             }
                statements;

  Ex:/*program for reverse of a number */
                     #include<stdio.h>
                     #include<conio.h>
                     void main()
                     {
                        int r,n,rev=0;
                        clrscr();
                        printf(“Enter value of n:”);
                        scanf(“%d”,&n);
                        while(n>0)
                         {
                                r=n%10;
                                rev=rev*10+r;
                                n=n/10;
                         }
                         printf(“\nReverse is %d”,rev);
                         getch();
                      }
2.      do-while loop (or) do-while statement:
                The do-while loop is an exit control loop. In this, first body of the loop is executed and then the condition is checked. If the condition is true, then the body of the loop is executed. If the condition is false, then it will exit from the loop.
The syntax for do-while loop is:
                                                do
                                                {
                                                    body of the loop(statements);
                                                }while(condition);
                                                statements;






















Ex:/*program for reverse of a number*/
                                #include<stdio.h>
                                #include<conio.h>
                                void main()
                                {
                                 int r,n,rev=0;
                                 clrscr();
                                 printf(“Enter value of n:”);
                                 scanf(“%d”,&n);
                 do
                                {
                                    r=n%10;
                                    rev=rev*10+r;
                                    n=n/10;
                                 }while(n>0);
                                  printf(“\n reverse is  %d” ,rev);
                                  getch();
                                }              
3.      for loop (or)  for statement :
                for loop is an entry control looping statement which repeats again and again till the condition is satisfied.It is a one step loop, which ‘initialize’, ‘check the condition and then ‘increment / decrement’.
The syntax is :
                                for(initial value; test condition; increment/decrement)
                                {
                                     body of the loop(statements);
                                }
                                statements;























In the above for loop, first the value is initialized, then in the loop the test condition is checked and further the loop will increment/decrement according to the requirement. After completion of the loop, i.e. when the condition becomes false then the statement will be executed.
Ex:/*program to print 1 to 10 numbers */
                #include<stdio.h>
#include<conio.h>
void main()
{
    int I;
    clrscr();
    printf(“the numbers from 1 to 10 are:”);
    for(i=1;i<=10;i++)
    {
       printf(“%d\n”,i);
    }
    getch();
}
Nested for:
                   When a for loop is executed within another for loop then it is called nested for loop. In this first the inner loop will be completed then the outer loop will be completed later according to the condition.  The syntax is:
   for(initial value-1; test condition-1; increment-1/decrement-1)
   {
       for(initial value-2; test condition-2; increment-2/decrement-2)
       {
                                Inner body of the loop(statements);
                       }
                      Outer body of the loop(statements);
                   }
                   Statements;
Ex:/*program to illustrate nested for loop*/
                   #include<stdio.h>
                   #include<conio.h>
                   void main()
                   {
                       int I,j,n;
                       clrscr();
                       printf(“Enter value of n:”);
                       scanf(“%d”,&n);
                       for(i=1;i<=n;i++)
                       {
                          for(j=1;j<=i;j++);
                          {
                                printf(“%d”,j);
                          }
                          printf(“\n”);
                       }
                       getch();
                   }
Output: Enter value of n 3
                   1
                   12
                   123

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