Factorial of a number N, (N!) is 1*2*3*4*5*…..*N. Here we’ll see how to write C program to calculate the factorial value of a number.
Here are the C functions that calculate the factorial value of a the input number.
Using FOR Loop
unsigned long factorial(int n) {
unsigned long f = 1;
int i;
for(i = 1; i <= n; i++) {
f *= i;
}
return f;
}Using WHILE Loop
unsigned long factorial(int n) {
unsigned long f = 1;
while(n) f *= n--;
return f;
}Using Recursion
unsigned long factorial(int n) {
if(n == 0) return 1;
return factorial(n-1) * n;
}Complete Program
Any one of the above functions can be used in the program.
#include <stdio.h>
unsigned long factorial(int n) {
unsigned long f = 1;
while(n) f *= n--;
return f;
}
int main()
{
int n;
unsigned long f = 0;
printf("Enter a number: ");
scanf("%d", &n);
if(n < 0) {
printf("Factorial not possible for a negative number.\n");
return 0;
}
f = factorial(n);
printf("Factorial of %d is %lu", n, f);
return 0;
}Here is the output of the program.
