Program to identify the prime number

Code:

#include<stdio.h>

#include<conio.h>

void main()

{

      int num,flag=0,a;

            printf("Enter an integer: ");

            scanf("%d",&num);

      //Logic for prime number

            if(num==2)

                  printf("%d is Prime Number.",num); 

            else

            {

                  for(a=2;a<num;a++)

                  {

                        if(num%a==0)

                              flag=1;

                  }

            }

            if(flag==1)

                  printf("%d is not a Prime Number.",num);

            else

                  printf("%d is Prime Number.",num);

      getch();

}

Result:

Enter an integer: 8

8 is not a Prime Number.

If you have any confusion about that program, contact me freely :)

Interchanging two variables without using the third one

Using less variables is a sign of good programming. Here's the example program to interchanging the values of two variables without using third variable.

Code:

#include<stdio.h>

#include<conio.h>

void main()

{

//Initialization

  int var1,var2; 

    printf("Enter two integers\n");

//Taking input from user

      printf("a = ");

      scanf("%d",&var1);

      printf("b = ");

      scanf("%d",&var2);

   var1=var1+var2;

   var2=var1-var2;

   var1=var1-var2;

    printf("a = %d\n",var1);

    printf("b = %d\n",var2);

  getch();

}

Result:

Enter two integers

a = 5

b = 11

a = 11

b = 5