# Program to Calculate Factorial of n Number

This article describes *how to calculate factorial of n number in C/C++*?. Let us describes about factorial number.

**What is Factorial!**

The factorial means to multiply a series of descending natural numbers. Its symbol is! And pronounced n factorial. But some people even say “4 shriek” or “4 bang”

In mathematics the factorial of a natural number n is the product of the positive integers less than or equal to n. It is written as n!

Examples:

0! = 1

1! = 1

2! = 2×1 = 2

3! = 3×2×1 = 6

4! = 4×3×2×1 = 24

5! = 5×4×3×2×1 = 120

**Where is Factorial Used?**

Factorials are used in many areas of mathematics. It is used particularly in Combinations and Permutations.

**What About Decimals?**

Can we have factorials for numbers like 0.6 or -5.217?

Yes we can! But you need to get into a subject called the “Gamma Function”.

**Program to Calculate Factorial of n Number (using for loop)**

#include

#include

int main(){

clrscr();

long double n,i,fact=1;

cout<<” ” This program will claculate Factorial of n number (using For loop). “”<<endl<<endl;

xx:

cout<<“How many numbers ?. Give a integer number.”<<endl;

cin>>n;

if (n<0) {

cout<<“Negative number not allow, Please give integer number.”<<endl;

goto xx;

}

for(i=1;i<=n;i++)

fact=fact*i;

cout<<endl;

cout<<“Factorial of “<<n<<” is : ” <<fact;

getch();

}

**Program to Calculate Factorial of n Number (using do-while loop)**

#include

#include

int main(){

clrscr();

long double n,i,fact=1;

cout<<” ” This program will show the Factorial of n numer (usin do-while loop). “”<<endl<<endl;

xx:

cout<<“Give how many numbers ?. Give a integer number.”<<endl;

cin>>n;

if (n<0) {

cout<<“Negative number is not allow, Please give integer number.”<<endl;

goto xx;

}

i=1;

do {

fact=fact*i;

i++;

}

while(i<=n);

cout<<endl;

cout<<“Factorial of “<<n<<” is : ” <<fact;

getch();

}

**Program to Calculate Factorial of n Number (using while loop)**

#include

#include

int main(){

clrscr();

long double n,i,fact=1;

cout<<” ” This program will show the Factorial of n number (using while loop).””<<endl<<endl;

xx:

cout<<“How many numbers ?.Give a integer number. “<<endl;

cin>>n;

if (n<0) {

cout<<“Negative number is not allow, Please give integer number.”<<endl;

goto xx;

}

i=1;

while(i<=n){

fact=fact*i;

i++;

}

cout<<endl;

cout<<“Factorial of “<<n<<” is : ” <<fact;

getch();

}