Before know the source code we need to understand the concept about primat number .

what is prime number?

>>The number which is only divisible by 1 or itself.

or

>>The number which do not come in others numbers multiplication table .

To check the given number is prime ,firstly user must input the number .After getting number from the user ,we need to divide that number by each 1 to n (input number) by using for loop .then we need to count how many times input number is perfectly divided.

If count is equal to 2 ,that means the input number is divided by 1 or itself,that means input number is a prime number.

The source code is given below and output also:

main()

{

int a,i,d;

printf(“enter a number to check prime\n “);

scanf(“%d”,&a);

for(i=1;i<=a;i++)

{

if(a%i==0)

{

d++;

}

}

if(d==2)

{

printf(“prime number”);

}

else

{

printf(“not a prime number”);

}

}

output:

enter a number to check prime 7 prime number