﻿ C Program: Check whether a given number is prime or not - w3resource

# C Exercises: Check whether a given number is prime or not

## C For Loop: Exercise-32 with Solution

Write a C program to determine whether a given number is prime or not.

The program should prompt the user for an integer input, then determine if the number has any divisors other than 1 and itself. If the number has no other divisors, it is prime; otherwise, it is not. The result should be displayed to the user.

Visual Presentation:

Sample Solution:

C Code:

``````#include <stdio.h> // Include the standard input/output header file.

void main(){

int num,i,ctr=0; // Declare variables for user input, loop control, and a counter.

printf("Input  a number: "); // Prompt the user to input a number.
scanf("%d",&num); // Read the input number from the user.

for(i=2;i<=num/2;i++){ // Start a loop to check for factors of the input number.
if(num % i==0){ // If the input number is divisible by 'i'.
ctr++; // Increment the counter.
break; // Exit the loop since a factor has been found.
}
}

if(ctr==0 && num!= 1) // If no factors were found and the number is not 1.
printf("%d is a prime number.\n",num); // Print that the number is prime.
else
printf("%d is not a prime number",num); // Print that the number is not prime.
}
```
```

Output:

```Input  a number: 13
13 is a prime number.
```

Flowchart:

C Programming Code Editor:

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