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C Program to Find the Factorial of a Number

In this article, we will learn about how to find and print the factorial of any given number, both with and without using a function. Here we have also created a recursive function to find out the factorial of any number. Here is the list of programs you will go through:

But before starting these programs, let's understand how the factorial of a number gets calculated.

How to find the factor of any number

To find the factorial f of any number, say n, use the formula

Factorial of n (n!) = (n)*(n-1)*(n-2)*....*3*2*1

Or

n! = 1*2*3*....*(n-2)*(n-1)*n

For example, find the factorial of 5 using the above formula.

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

So the factorial of 5 is 120. Now let's move on and implement it in a C program.

In C, find the Factorial of a given number

To find the factorial of any given number in C programming, you have to ask the user to enter the number. Now find the factorial of that number using the above formula, as shown in the program given below. As you can see from the formula, if a number is n, then multiplication occurs n times.

For example, if the number is 5, multiplication occurs 5 times, resulting in 5*4*3*2*1. So, in this case, a loop that runs n times is required.

#include<stdio.h>
#include<conio.h>
int main()
{
    int num, i, fact=1;
    printf("Enter any number: ");
    scanf("%d", &num);
    for(i=num; i>0; i--)
        fact = fact*i;
    printf("\nFactorial of %d = %d", num, fact);
    getch();
    return 0;
}

Because the program was written in the Code::Blocks IDE, you will see the following output after a successful build and run:

c program find factorial of number

Now supply any number, say 5, and press the ENTER key to see the factorial of 5 as output, as shown here:

find factorial c

Program Explained

Using a Function, find the Factorial of a Number

This program does the same job, but using the user-defined function findFact().

#include<stdio.h>
#include<conio.h>
int findFact(int);
int main()
{
    int num, fact;
    printf("Enter any number: ");
    scanf("%d", &num);
    fact = findFact(num);
    printf("\nFactorial of %d = %d", num, fact);
    getch();
    return 0;
}
int findFact(int n)
{
    int i=n, f=1;
    while(i>0)
    {
        f = f*i;
        i--;
    }
    return f;
}

Using Recursion, find the Factorial of a Number

Here is another program that will calculate the factorial of any given number using a recursive function:

#include<stdio.h>
#include<conio.h>
int findFact(int);
int main()
{
    int num, fact;
    printf("Enter the number: ");
    scanf("%d", &num);
    fact = findFact(num);
    printf("Factorial = %d", fact);
    getch();
    return 0;
}
int findFact(int val)
{
    if(val==1)
        return val;
    else
        return val*findFact(val-1);
}

Here is the final snapshot of the sample run:

c factorial using recursive function

Program Explained

Find the Factorial of All Numbers in a Range

Now this is the last program that will find the factorial of all numbers in a given range. For example, if the user enters 1 and 10 as two numbers (the range), Then the program will find and print the factorial of all numbers from 1 to 10.

#include<stdio.h>
#include<conio.h>
int findFact(int);
int main()
{
    int num1, num2, i;
    long int fact;
    printf("Enter Range: ");
    scanf("%d %d", &num1, &num2);
    if(num1<num2)
    {
        for(i=num1; i<=num2; i++)
        {
            fact = findFact(i);
            printf("\nFactorial of %d = %ld", i, fact);
        }
    }
    else
    {
        for(i=num2; i<=num1; i++)
        {
            fact = findFact(i);
            printf("\nFactorial of %d = %ld", i, fact);
        }
    }
    getch();
    return 0;
}
int findFact(int n)
{
    int i=n;
    long int f=1;
    while(i>0)
    {
        f = f*i;
        i--;
    }
    return f;
}

Here is its sample run:

find factorial of all number in range c

The same program in different languages

C Quiz

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