Value returning function help

Hi,

Code:

#include <iostream>
#include <string>
#include <cmath>
#include <fstream>
#include <iomanip>

using namespace std;

int main()
{
	int OPTION= 99;
	while(OPTION !=0 )
	{
		
        int MENU();			
		int SIDE;
		double AREAOFSQUARE;
		OPTION=MENU();
				
		if (OPTION == 1)
			{
				cout<<"Enter the length of the side";
				cin>>SIDE;
				cout<<"The area of the square is: "<<AREAOFSQUARE(SIDE)<<endl;
			}
			else
				cout<<"..."<<endl;
	}
	
}
int MENU()
{
	int CHOICE;
	cout<<"1.)  Compute area of a square."<<endl;
	cout<<"Select one."<<endl;
	cin>>CHOICE;
	return CHOICE;
}
double AREAOFSQUARE(double SIDE)
{
	return SIDE * SIDE;
}

for some reason the function "AREAOFSQUARE" is not being called correctly. it gives me this error: "error C2064: term does not evaluate to a function taking 1 arguements."
I looked at examples in my book and the tutorials, but i can not find what i am doing wrong.

Code:

double AREAOFSQUARE;

That's a variable. Compiler thinks you tried to use it as a function or something.

if i delete that part then it gives me these errors:

error C3861: 'AREAOFSQUARE': identifier not found, even with argument-dependent lookup

error C2365: 'AREAOFSQUARE' : redefinition; previous definition was a 'formerly unknown identifier'

Function declarations needed. Either globally or locally to main.

Code:

int main()
{
    int MENU(void);
    double AREAOFSQUARE(double);

	int OPTION= 99;
	while(OPTION !=0 )
	{
		int SIDE;
		OPTION=MENU();
				
		if (OPTION == 1)
			{
				cout<<"Enter the length of the side";
				cin>>SIDE;
				cout<<"The area of the square is: "<<AREAOFSQUARE(SIDE)<<endl;
			}
			else
				cout<<"..."<<endl;
	}
	
}
int MENU()
{
	int CHOICE;
	cout<<"1.)  Compute area of a square."<<endl;
	cout<<"Select one."<<endl;
	cin>>CHOICE;
	return CHOICE;
}
double AREAOFSQUARE(double SIDE)
{
	return SIDE * SIDE;
}

Code:

#include <iostream>
#include <string>
#include <cmath>
#include <fstream>
#include <iomanip>

using namespace std;

double AREAOFSQUARE(double);
int MENU(void);

int main()
{
	int OPTION= 99;
	while(OPTION !=0 )
	{
		int SIDE;
		OPTION=MENU();
				
		if (OPTION == 1)
			{
				cout<<"Enter the length of the side";
				cin>>SIDE;
				cout<<"The area of the square is: "<<AREAOFSQUARE(SIDE)<<endl;
			}
			else
				cout<<"..."<<endl;
	}
	
}
int MENU()
{
	int CHOICE;
	cout<<"1.)  Compute area of a square."<<endl;
	cout<<"Select one."<<endl;
	cin>>CHOICE;
	return CHOICE;
}
double AREAOFSQUARE(double SIDE)
{
	return SIDE * SIDE;
}

Oh, i totally forgot about declaring them first. Thank you!

I don't think uppercase functions and variables look good. I'd prefer only the first letter uppercase or the first letter of every word uppercase or totally lowercase.
I only use uppercase names for macros.