read-a-number-and-check-it-is-prime-or-not-using-do-while.c

   #include<stdio.h>
   void main()
   {
       int Number,i,flag;

       printf("Enter a Number :");
       scanf("%d",&Number);

       i = 2; // because every number is divesible by 1 ;
       flag = 1; // we can give any value to flag.
       
       do 
       {

            if ( Number % i == 0 )
                  flag = 0;        // if number divide by any number from 1 to number-1 then flag become 0.
            i++;  

       }while( i < Number ); // because each number is divesible by itself so we move from 2 to Number-1.


       if( flag == 0 || Number == 1 )
              printf("Enterd number is not an prime number");
       else
              printf("yes enterd number is an prime number");

   }