**Write
a C program to check whether the given number is a prime**

A prime number is a
natural number that has only one and itself as factors. Examples: 2, 3, 13 are
prime numbers.

**Program:**

#include
<stdio.h>

main()

{

int n, i, c = 0;

printf("Enter
any number n: \n");

scanf("%d",
&n);

/*logic*/

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

{

if (n % i == 0)

{

c++;

}

}

if (c == 2)

{

printf("n is a
Prime number");

}

else

{

printf("n is not
a Prime number");

}

return 0;

}

**Output:**

Enter any number n: 7

n is Prime

**Explanation
with examples:**

consider a number n=5

for(i=0;i<=n;i++)
/* for loop is executed until the n value equals i */

i.e.
for(i=0;i<=5;i++) /* here the for loop is executed until i is equal to n */

1st iteration:
i=1;i<=5;i++

here i is incremented
i.e. i value for next iteration is 2

now if(n%i==0) then c
is incremented

i.e.if(5%1==0)then c
is incremented, here 5%1=0 thus c is incremented.

now c=1;

2nd iteration:
i=2;i<=5;i++

here i is incremented
i.e. i value for next iteration is 3

now if(n%i==0) then c
is incremented

i.e.if(5%2==0) then c
is incremented, but 5%2!=0 and so c is not incremented, c remains 1

c=1;

3rd iteration:
i=3;i<=5;i++

here i is incremented
i.e. i value for next iteration is 4

now if(n%i==0) then c
is incremented

i.e.if(5%3==0) then c
ic incremented, but 5%3!=0 and so c is not incremented, c remains 1

c=1;

4th iteration:
i=4;i<=5;i++

here i is incremented
i.e. i value for next iteration is 5

now if(n%i==0) then c
is incremented

i.e. if(5%4==0) then
c is incremented, but 5%4!=0 and so c is not incremented, c remains 1

c=1;

5th iteration:
i=5;i<=5;i++

here i is incremented
i.e. i value for next iteration is 6

now if(n%i==0) then c
is incremented

i.e. if(5%5==0) then
c is incremented, 5%5=0 and so c is incremented.

i.e. c=2

6th iteration:
i=6;i<=5;i++

here i value is 6 and
6<=5 is false thus the condition fails and control leaves the for loop.

now if(c==2) then n
is a prime number

we have c=2 from the
5th iteration and thus n=5 is a Prime number.