C program to find factorial of a number

In this tutorial, we will discuss the concept of C program to find factorial of a number

Factorial is a product of all positive descending integer begins with a specified number (n) and calculates up to one

Example

factorial of 5 is

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

factorial of 4 is

4!=4*3*2*1=24

The factorial of a positive number n is given below

factorial of n is

n!=n*(n-1)*....2*1

There are many ways to calculate a factorial using C programming language. some of them are described as below.

the user can provide numbers as they wish and get the factorial according to their input

Code to find factorial of a number

Find factorial using for loop

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int n,i,factorial=1;
    printf("Enter an integer..: ");
    scanf("%d",&n);

    if(n<0){
        printf("Factorial doesn't available to a negative number");
    }

    else{
        for(i=1; i<=n; i++){
            factorial*=i;  //this is equal to factorial=factorial*1

        }
           printf("Factorial of %d is = %d ",n,factorial);
    }
    getch();
    return 0;
}

When the above code is executed, it produces the following results

case 1

Enter an integer..:8
Factorial of 8 is= 40320

case 2

Enter an integer..:0
Factorial of 0 is= 1

case 3

Enter an integer..:-3
Factorial doesn't available to a negative number

Find factorial using the while loop

Program 2

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int n,i,factorial=1;
    printf("Enter an integer..: ");
    scanf("%d",&n);

    if(n<0){
        printf("Factorial doesn't available to a negative number");
    }

    else{
            i=1;
        while(i<=n){
            factorial*=i;  //this is equal to factorial=factorial*1
           i++;
        }
           printf("Factorial of %d is = %d",n,factorial);
    }
    getch();
    return 0;
}

When the above code is executed, it produces the following results

Enter an integer..:5 
Factorial of 5 is= 120

Find factorial using the do-while loop

Program 3

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int n,i,factorial=1;
    printf("Enter an integer..: ");
    scanf("%d",&n);

    if(n<0){
        printf("Factorial doesn't available to a negative number");
    }

    else{
            i=1;
    do{
        factorial*=i;  //this is equal to factorial=factorial*1
           i++;

        }while(i<=n);
           printf("Factorial of %d is = %d",n,factorial);
    }
    getch();
    return 0;
}

When the above code is executed, it produces the following results

Enter an integer..:6 
Factorial of 6 is= 720

Find factorial using recursion

#include <stdio.h>
#include <stdlib.h>

long factorial(int);  //function declaration
int main()
{
    int n;
    long fact;

    printf("enter the integer to find factorial\n");
    scanf("%d", &n);

    if(n<0)
        printf("Factorial doesn't available to a negative number");
    else{
        fact=factorial(n);//call the method
        printf("%d! = %ld\n",n,fact);
    }
    getch();
    return 0;
}
long factorial(int n)
{

    if(n==0)
        return 1;
    else
        return(n*factorial(n-1));
}

When the above code is executed, it produces the following results

enter the integer to find factorial
6
6!=720

Find factorial using the function

#include <stdio.h>
#include <stdlib.h>
long factorial(int);
int main()
{
    int num;
    long fact=1;

    printf("Enter a number to calculate factorial\n");
    scanf("%d",&num);


    printf("%d! = %ld\n",num,factorial(num));
    getch();
    return 0;
}
long factorial(int n)
{
    int i;
    long result=1;
    for(i=1; i<=n; i++)
        result=result*i;
    return result;
}

When the above code is executed, it produces the following results

Enter a number to calculate factorial
6
6!=720

C program to find factorial of a number