C Program to Check Whether a Number is Prime or Not - Programming 180

Before going to write a c program for Prime number first you have to know about prime number , if statements, if-else statements.
A number that has factors as one and itself are known as prime numbers. For example number 3 has 1 and 3 as a factors and number 6 has 1, 2, 3, 6 as a factors. Therefore 3 is a Prime number and 6 is not a prime number.

To check a given number prime or not we have to use for loop and if ...else statements in c program. A positive number is said to be a prime number which is greater than 1 must have factors one and itself is called prime number.2, 3, 5, 7 etc. are prime numbers.

Now we will write an algorithm to Prime number.

Algorithm to check Prime number.

1. Start.
2. Input a number (say n)
3. Divide number n from 0 to n.
4. If n%2=0 increment count.
5. If count=2 then print prime number.
6. Else print not a prime number.
7. Stop.

Example #1: Program to Check prime Number

#include<stdio.h>
main() 
{ 
 int i,n,count=0; 
 printf("Enter any number to check :");
 scanf("%d",&n); 
 for(i=0;i<=n;i++) 
 { 
  if(n%i==0)
  { 
    count++; 
  } 
  if(count==2)
 printf("%d is prime number",n);        
   else 
 printf("%d is not a prime number",n); 
 
 }

Output:

Enter any number to check :7
Given number is not a prime number