C++ program to find factorial of number in C++

What is a Factorial of a number 'n'? 

  The factorial of a number 'n' is theproduct of all number from 1 upto the number 'n'

it is denoted by n!.  For example n=5 then factorial of 5 will be 1*2*3*4*5= 120. 5!= 120
Factorial program C++ Logic:

• First think what is the factorial of a number? How mathematically it can be calculated.
•  If you got this info then it will be very easier to make a C++ Programlogic to find the factorial.
•  User enters a number and we have to multiply all numbers upto entered number.
• Like if user enters 6  then Factorial should be equal to factorial= 1*2*3*4*5*6.
• In this case a for Loop will be very helpful. It will start from one and multiply all numbers upto entered number after it loop will be terminated.
• Take a variable and initialized it to 1 and in loop store multiplication result into it like in below program a variable 
• Factorial is used for this purpose.what is we does not initialized it to 1 and initialized it to zero or remain it uninitialized. In case of 0 our result will be zero in case of any number entered
• In case of not initializing it our answer will correct mostly but if variable contains garbage value then we will not be able to get correct result. 
• It is recommended that to initialize it to one.C++ code to find prime number using for loop

C++ code to find prime number using for loop

#include<iostream>

using namespace std;
int main()
{
    int num,factorial=1;
    cout<<" Enter Number To Find Its Factorial:  ";
    cin>>num;
    for(int a=1;a<=num;a++)
    {
        factorial=factorial*a;
    }
cout<<"Factorial of Given Number is ="<<factorial<<endl;
    return 0;
}