Here you will learn to calculate the factorial of a number using for loop in C++ in this example.
The factorial of a number is the product of all integers from 1 to that number. Factorial is not defined for negative numbers, and the factorial of zero is one. An exclamation mark indicates the factorial of a number '!'.
n! = 1 * 2 * 3 * 4 *……..* n.
5! = 1*2 *3*4*5 = 120.
The user is asked to enter a positive integer. Read the number to the integer variable n. declare a long double variable fact = 1.0;Long double refers to a floating-point data type that is often more precise than double precision.
for loopNote: The factorial of zero is defined as one ie., 0 ! = 1
for ( i = 1; i<= n; i++ )
{ fact *= i; }
Print fact and finish the program.
Step 1: Call the header file iostream.
Step 2: Use the namespace std.
Step 3: Open the integer type main function; int main().
Step 4: Declare integer variables; n, fact
Step 5: Print a message to enter a positive integer.
Step 6: Read the number into the variable n.
Step 7: Print an error message if n < 0. Else go to step 8
Step 8: for i = 1 to n; fact *= i; print fact
Step 9: print fact = 1 for 0!.
Step 10: Exit.
#include <iostream>
using namespace std;
int main() {
int n;
long double fact = 1.0;
cout << "Enter a positive integer: ";
cin >> n;
if (n < 0)
cout << "Error! Factorial of a negative number doesn't exist.";
else {
for(int i = 1; i <= n; ++i) {
fact *= i;
}
cout << "Factorial of " << n << " = " << fact;
}
return 0;
}
Run 1 Enter a positive integer: 9 Factorial of 9 = 362880 Run 2 Enter a positive integer: -8 Error! Factorial of a negative number doesn't exist. Run 3 Enter a positive integer: 0 Factorial of 0 = 1
