# C program for factorial | factorial program in c

Hey, guys here is another useful c program for factorial. Today we will learn factorial program in c. The program asks the user to input a number and the program give an output as factorial of a given number based on user input. so let’s start.

## what is factorial?

the factorial of a non-negative integer *n*, denoted by *n*! it is the product of all positive integers less than or equal to *n*.

For example,

factorial of 5! is 120

- 5!=5*4*3*2*1=120

factorial of 6! is 720

6!=6*5*4*3*2*1=720

**Note- Factorial of 1 is 1 and factorial of 0 is also 1.**

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## C program for factorial using for loop

#include <stdio.h> int main() { int n, i,f=1; printf("Enter an integer Number: "); scanf("%d",&n); if (n < 0) printf("Factorial of a negative number doesn't exist"); else { for(i=1; i<=n; ++i) { f= f*i; } printf("Factorial of %d = %d", n, f); } return 0; }

## factorial program in c using while loop

#include <stdio.h> int main() { int n, i,f=1; printf("Enter an integer Number: "); scanf("%d",&n); i=n; if (n < 0) printf("Error! Factorial of a negative number doesn't exist."); else { while(n!=0) { f= f*n--; } printf("Factorial of %d = %d", i, f); } return 0; }

output:-

Enter an integer Number: 4

Factorial of 4 = 24

Enter an integer Number: 5

Factorial of 5 = 120

Enter an integer Number: 0

Factorial of 0 = 1

Enter an integer Number: 1

Factorial of 1 = 1

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