C While Loop

A while loop is a control statement using which the programmer can give instructions to the computer to execute a set of statement repeatedly as long as specified condition is satisfied. Ones the specified condition is false control comes out of the loop.

How while Loop Works

• Step 1:-
  The initialization statement is executed first
• Step 2:-
  Then, the test expression is evaluated. If the test expression is evaluated to false, then the while loop gets terminated and the control comes out of the while loop.
• Step 3:-
  if the test expression is evaluated to true,The statements defined inside the while loop will repeatedly execute until the given condition fails.
• Step 4:-
  After successful execution of statements inside the body of the while loop, the update expression is executed.
• Step 5:-
  Again the test expression is evaluated.

Example with dry Run Concepts

 #include<stdio.h>
 #include<conio.h>
 void main()
 {
 int i=1;
 while(i<=5)
 {
 printf(“%d\n”,i);
 i++;   
 }
 getch();
 }

Program Explanation

• Step 1:-
  We declared integer variables called i. The initialization statement is executed. i.e i=1
• Step 2:-
  Then, the test expression is evaluated. i.e i is less than or equals to 5 or not (i <=5 ) hear condition is true so statements inside the body of the while loop are executed, and it will print the value of i i.e 1
• Step 4:-
  After successful execution of statements inside the body of the loop, the update expression (i.e i++) means it incremented by 1 now the value of i is 2
• Step 5:-
  Again the test expression is evaluated. and repeat step 2 till the condition is false
• Step 5:-
  when the condition is false means the value of i will be 6 then while loop gets terminated and the control comes out of the loop.

 #include<stdio.h>
 #include<conio.h>
 void main()
 {
    int n,s=0;
	printf("Enter a Number");
	scanf("%d",&n);
    while(n!=0)
   {
      a=n%10;
      n=n/10;
      s=s+a;	  
    }
	printf("%d",s);
 getch();
 }

Program Explanation

• Step 1:-
  We declared integer variables called n and s;
• Step 2:-
  hear we initialization s=0 because we will have to sum of each digits so it not initialization garbage value
• Step 3:-
  hear we use % and / operator as we know that any number % by 10 remainders will be last digits and if any number / by 10 quotient will be before last digits
  Let`s n=123 and we have to sum of s=1+2+3 i.e 6
  r=n%10; value of r will be 3 and q=n/10 value of q will be 12
• Step 4:-
  Next, the test expression is evaluated. i.e n is not equals to 0 (n !=0 ) hear condition is true so statements inside the body of the while loop are executed, and the first iteration value of a will be 3 and value of n will be 12
• Step 5:-
  Again the test expression is evaluated. and repeat step 2 till the condition is false
• Step 6:-
  when the condition is false means the value of n will be 0 then while loop gets terminated and the control comes out of the loop.
• Step 7:-
  After terminated loop sum of each digits print

C While loop MCQ Question

int main()
{
  int a=0, b=0;
  while(++a < 4)
     printf("%d ", a);
  while(b++ < 4)
     printf("%d ", b);
  return 0; 
}

1. 0 1 2 3 1 2 3 4
2. 1 2 3 1 2 3 4
3. 1 2 3 4 1 2 3 4
4. 1 2 3 4 0 1 2 3

1. while(condition)
   {
       //statements
   }
   

2. (condition)
   {
       //statements
   }while
   

3. do(condition)
   {
       //statements
   }while
   

4. for(condition)
   {
       //statements
   }
   

int main()
{
    while(true)    
    {
        printf("RAJ");
        break;
    }
    
    return 0;
}

1. RAJ
2. RAJ is printed unlimited number of times.
3. No output
4. Compiler error.

int main()
{
    int a=5;
    
    while(a=123)    
    {
        printf("RAJ\n");
        break;
    }
    printf("RANCHI");
    
    return 0;
}

1. RAJ
2. RAJ
   RANCHI
3. No output
4. Compiler error.

int main()
{
    int a=5;
    
    while(a >= 3);
    {
        printf("RAJ\n");
        break;
    }
    printf("RANCHI");
    
    return 0;
}

1. RAJ
2. RAJ
   RANCHI
3. No output
4. None of the above