Factorial program in C programming language: C program to find and print factorial of a number, three methods are given, the first one uses for loop, the second uses a function to find factorial and the third uses recursion. Factorial is represented using '!', so five factorial will be written as (5!), n factorial as (n!). Also, n! = n*(n-1)*(n-2)*(n-3)...3.2.1 and zero factorial is defined as one i.e. 0! = 1.

## Factorial program in C using for loop

Here we will find factorial using for loop.

#include <stdio.h> int main() { int c, n, fact = 1; printf("Enter a number to calculate its factorial\n"); scanf("%d", &n); for (c = 1; c <= n; c++) fact = fact * c; printf("Factorial of %d = %d\n", n, fact); return 0; }

Output of C factorial program:

Download Factorial program.

## Factorial program in C using function

#include <stdio.h> long factorial(int); int main() { int number; long fact = 1; printf("Enter a number to calculate its factorial\n"); scanf("%d", &number); printf("%d! = %ld\n", number, factorial(number)); return 0; } long factorial(int n) { int c; long result = 1; for (c = 1; c <= n; c++) result = result * c; return result; }

## Factorial program in C using recursion

#include<stdio.h> long factorial(int); int main() { int n; long f; printf("Enter an integer to find its factorial\n"); scanf("%d", &n); if (n < 0) printf("Factorial of negative integers isn't defined.\n"); else { f = factorial(n); printf("%d! = %ld\n", n, f); } return 0; } long factorial(int n) { if (n == 0) return 1; else return(n * factorial(n-1)); }

Recursion is a technique in which a function calls itself, for example, in the above code factorial function is calling itself. To solve a problem using recursion you must first express its solution in recursive form.