C Program to Calculate Factorial Value

C Program To Find Factorial of a Number

This c program is used to find the factorial value for any number.

Factorial Algorithm:

Factorial of a Number = 1*2* .... (Number-1)*Number.

Finds Factorial of a Number using while loop

#include<stdio.h>                                                               
                                                                                
void main()                                                                     
{                                                                               
    int num, i=1, factorial = 1;                                                
                                                                                
    printf("Enter number: ");                                                   
    scanf("%d",&num);                                                           
                                                                                
    if (num < 0)                                                                
        printf("Error - Negative Number.");                                     
    else                                                                        
    {                                                                           
         while(i <= num)                                                        
        {                                                                       
            factorial *= i;                                                     
            i++;                                                                
        }                                                                       
        printf("Factorial of %d: %d", num, factorial);                          
    }                                                                           
}                                                                    
                                                                                  

$ cc factorial.c
$ ./a.out 
Enter number: 5
Factorial of 5: 120
$ vi factorial.c
[$ ./a.out 
Enter number: -3
Error - Negative Number.

Finds Factorial of a Number using for loop

#include                                                               
                                                                                
void main()                                                                     
{                                                                               
    int num, i=1, factorial = 1;                                                
                                                                                
    printf("Enter number: ");                                                   
    scanf("%d",&num);                                                           
                                                                                
    if (num < 0)                                                                
        printf("Error - Negative Number.");                                     
    else                                                                        
    {                                                                           
        for(i=1;i <= num;i++)                                                   
        {                                                                       
            factorial *= i;                                                     
        }                                                                       
        printf("Factorial of %d: %d", num, factorial);                          
    }                                                                           
} 

$ cc factorial.c
$ ./a.out 
Enter number: 4
Factorial of 4: 24

Finds Factorial of a Number using Recursive Function

Recursive function is a function which calls itself.

#include <stdio.h>
                                                                                
int factorial(int);                                                             
                                                                                
void main()                                                                     
{                                                                               
    int num, i=1, factorial_val = 1;                                            
                                                                                
    printf("Enter number: ");                                                   
    scanf("%d",&num);                                                           
                                                                                
    if (num < 0)                                                                
        printf("Error - Negative Number.");                                     
    else                                                                        
    {                                                                           
        factorial_val = factorial(num);                                         
        printf("Factorial of %d: %d", num, factorial_val);                      
    }                                                                           
}                                                                               
                                                                                
int factorial(int num)                                                          
{                                                                               
    if(num > 1)                                                                 
        return (num * factorial(num-1));                                        
    else                                                                        
        return 1;                                                               
}  

$ cc factorial.c
$ ./a.out 
Enter number: 6
Factorial of 6: 720