## Factorial program in c++

In this C++ program, we are going to determine the factorial of a number using functions. Here I will provide you different ways to find the factorial of a number in c++. First, we use for loop, then functions, and at last recursion.

## Factorial program in c++ using for loop.

Source code:

`#include<iostream.h>#include<conio.h>void main(){int num,i;clrscr();cout<<"n Enter a Number:";cin>>num;for(i=num-1;i>=1;i--)num=num*i;cout<<“n factorial of a number”;cout<<“n entered by you”;cout<<num;getch();}`
Output:

## Factorial program in c++ using functions

Source code:

`#include<iostream.h>#include<conio.h>void factorial(int s);void main(){clrscr();int num;cout<<"n Enter a number:";cin>>num;factorial(num);getch();}void factorial(int s){int fact=1;for(int i=s;i>=1;i--)fact*=i;cout<<"Factorial of "<<s;cout<<" is "<<fact;}`

Output:

Enter a number:6
Factorial of 6 is 720

## Factorial program in c++ using recursion

Source code:

`#include<iostream.h>#include<conio.h>int factorial(int s);void main(){clrscr();int num,fact;cout<<"n Enter a number:";cin>>num;fact=factorial(num);cout<<"Factorial of "<<num;cout<<" is "<<fact;getch();}int factorial(int s){int fact_num;if(s==1)return(1);elsefact_num=s*factorial(s-1);return(fact_num);}`

Output:

`Enter a number: 5`
`Factorial of 5 is 120`

Factorial:
5! =5*4*3*2*1 = 120
n! = n*(n-1)*n-2)*…..*1

## Algorithm to make a C++ Program to Find Factorial of a Number

• Let the number given by the user is “n”.
• Now we initialize loop counter with one less than the number given by the user “i= n-1”.
• The testing condition will be that the loop counter should be greater than and equal to 1 “i>=1″.
• Now we have to decrease the value of i by one “i=i-1” or “i–“.
• for(i=n-1;i>=1;i–)
• We will multiply num by i and stores its value in num.
• num=num*i;
• we have to just print the value of num which will print the factorial of that number entered by the user.