Disclaimer: I don't want someone to give me the answer, I just need a little guidance.

Ok, the program I am supposed to code is using Fibonacci's numbers.(Yes, this is an assignment) I thought I had the answer, so I got to coded. But my program keeps yielding a ridiculous random number.
The assignment is
" Assume that green crud grows at the rate of Fibonnaci's numbers and has a period of 5 days. Hence, if a green crud population starts out as 10 pounds of crud, then in 5 days there is still 10 pounds; in 10 days there is 20 pounds of crud, in 15 days 30 pounds, in 20 days 50 pounds, and so forth. Write a program that takes both the initial size of the crud and a number of days as input and that outputs the number of pounds of green crud after that many days. Assume that the population size is the same for four days and then increases every fifth day."

Here is my source code:


[Edited by - Blckknight118 on October 18, 2010 6:20:40 PM]

I don't understand, I already set the parameters once I declared the function greencrud.

I revised my code, but when I try to call numberof_crud it says it is undefined.

That's because in your main() function you never define a variable named numberof_crud. You do have some variables named crud_days and amount_crud. Maybe you should try using those.

Because you do not define numberof_crud in main.

When you call a function you have to pass the information (paramaters) it asks for. The function takes a copy of that information and runs with it.

But the parameters must be local or global variables available in the scope (in this case: 'main') that is calling the function.

You can also pass constants (as in actual numbers)

I still don't understand....I returned the value of numberof_crud at the end of the greencrud function. Also, I declared the parameters before. This is sort of confusing me.

Ok.

Each function works an a separate 'component' of a program. You have to think of both main and greencrud as separate entities.

greencrud requires three pieces of information to do its stuff. When you call the function the call (in this case, in main) must provide that information.

---Lesson on parameters---
Consider the following:

int Add(int Value1,int Value2)
{
return Value1+Value2;
}

The above function needs two numbers and it will add them together.

Lets look at ways we can use this function:

main()
{
int A=5;
int B=7;
int Result=Add(A,B);
}

Add needs two numbers, in the above we gave it A and B which at that time contained the values 5 and 7 respectively.

As a result the Add function was called. Its Parameters (Value1 and Value2) were set to 5 and 7 (the contents of A & B, in the order they are given). The function is executed with those values.

But although 'Param1' and 'A' now contain the same value (5) they are separate variables. If Add was to change Param1 to something A would NOT be changed. They are separate.

The Add function however simply adds those two and returns the result. Therefore our program now returns to main and 'Result' becomes 12.

Because Add takes an int, we can also pass real numbers. We can do this:

main()
{
int A=5;
int Result=Add(A,27);
}

The value of 'Result' would now be set to 32.

The fact you have named the parameters in 'greencrud' witht he same names as you use for variables in 'main' is irrelevant, they are separate entities.

Only if you declare them globally can they be 'shared', but that is a later lesson.