Little help with comments

[badcoder]

I have managed to write a simple program to display the factorials of each number up to 12, however I'm having trouble explaining each part of the code as it has took me lots of trial and error to get it to work. Any help is appreciated no matter how brief.

  #include <iostream>
 
using namespace std;
 
int main() //main function
{
    unsigned long int a, b, c;
    for (a=1;a<=12;a++)
    {
 
        b=1;
        for (c=1;c<=a;c++)
            b=b*c;
        cout << "The factorial of " << a << " is - " << b << endl;
 
    }
    system("pause");
    return 0;
}

[ne555]

Before starting to code write the purpose of the snip.
then write the pseudo-code.

After that, write below each line of pseudo-code the c++ code that would solve it.

There, you've got your code commented.

[Duthomhas]

[edit] Disregard; I read "Fibonacci" when OP said "Factorial". Oops!

The program is not correct. Factorial is 1, 1, 2, 3, 5, 8, 13, ...

Commentary helps you explain to yourself what you are doing. If the only commentary you have is "trial and error and seems to work", I've learned (from much experience) that it is an indication that the program is probably wrong.

To compute the factorial, you need three values: the current value (being computed) and the two values that came before that.

For example:

  int a = 1;
  int b = 1;
  int c = a + b;

Once you get the current value, you can forget the smallest value:

  a = b;
  b = c;

And you can compute the next value:

  c = a + b;

You only have to do that N-2 times. (Do you know why you don't have to do it for N=1 or N=2?)

Hope this helps.

[PCrumley48]

Wow, misunderstanding!

1,1,2,3,5,8 . . . is fibonacci series, not factorial!

Factorial is n * (n-1) * (n - 2) . . . * (1)

As to comments; Like ne555 said, Start by breaking the description of what you need to do into sentences:

1. For each integer from 1 to 12
2. Determine the factorial of the integer where factorial = count!
3. Display the count and the factorial of the count

[Duthomhas]

Holy mis-read, Batman!

:-@

Sorry OP.

[badcoder]

You had me scared then, I was looking at my code like s**t haha! Thanks for the help and feedback guys much appreciated.