Loop Control Statement

Loop control statements in c are used to perform looping operations until the given condition is true. Control comes out of the loop statements once condition becomes false. Loops are used to repeat a block of code.
There are 3 types of loop control statements in C language. They are,
1. while
2. do-while
3. for

1. While statement:
   The while statement continuously executes a block of statements until given condition is false.
   –> The while loop evaluates the test expression.
   –> If the test expression is true, codes inside the body of while loop is evaluated.
   –> Then, the test expression is evaluated again. This process goes on the test expression is false. 
   –> When the test expression is false, while loop is terminated.
   Syntax:
   while(expression)
   {
     statement(s)
   }
   Example:
   #include<iostream>
   using namespace std;
   void main()
   {
     int num, i=1, factorial=1;
     cout<<“Enter a positive integer:”;
     cin>>number;
     while (i<=number)
     {
       factorial=factorial*i’
       i++;
     }
     cout<<“Factorial of “<<number<<“=”<<factorial;
   }
2. do…while Loop:
   The do…while loop is a variant of the while loop with one important difference. The body of do…while loop is executed at least once. Then, only the test expression is checked.
   –> The code inside while loop is executed at least once. Then the test expression is checked.
   –> If the test expression is true, then the body of loop is executed. This process continues until the test expression becomes false.
   –> When the test expression is false, do…while loop is terminated.
   Syntax:
   do
   {
     statements;
   }while(test_Expression);
   Example:
   #include<iostream>
   using namespace std;
   void main()
   {
     float sum=0.0, num;
     do
     {
       cout<<“Enter a number:”;
       cin>>num;
       sum+=num;     //sum=sum+num
     }while(num!=0.0)
      cout<<“Total sum=”<<sum
   }
3. for Loop:
   A for loop is a repetition control structure that allows to write a loop that needs to execute a specific number of times.
   –> The initialization is executed once at the beginning.
   –> Then, the test expression is evaluated.
   –> If the test expression is false, for loop is terminated. But if the test expression is true, code inside the loop is executed and the expression is updated.
   –> Again, the test expression is evaluated and this process is repeated until the test expression is false.
   Syntax:
   for(initialization; condition; increment/decrement)
   {
     statements;
   }
   Example:
   #include<iostream>
   using namespace std;
   void main()
   {
     int i, n, fact=1;
     cout<<“Enter a positive integer:”
     cin>>n;
     for(i=1; i<=n; i++)
     {
       fact*=i;      //fact=fact*i
     }
     cout<<“Factorial of “<<n<<“=”<<fact;
   }