I understand how functions work, but if i'm unable to utilize it in a simple program, i guess i dont entirely understand it.

Anywho, i have to make a program where the users enter in an upper limit and a lower limit and the resrictions are....

y=-x when x<0
y=x^2 when 0<=x<=2
x>2 when y=4

Also the user gets to enter in an amount to increment.

heres an example, the user enters in -3 for lower and 3 for upper, it should display this...

xvalue yvalue
-3 3
-2.50 2.50
...... ......
..... ......
0 0
.50 .50
..... .......
..... ......
2 4
2.5 4
3 4

i got this far in my code...

Code:
float slope(int x, int y);

using namespace std;

void main()
{	float upnum, lownum, inc, a;

	cout << "Slope Function Program" << endl;

	cout << "Enter Lower Limit: " << endl;
	cin >> lownum;

	cout << endl;

	cout << "Enter Upper Limit: " << endl;
	cin >> upnum;

	cout << endl;

	cout << "Enter Increment: " << endl;
	cin >> inc;

	cout << endl;

	cout << left << setw(8) << "X Value" << " " << left << setw(8) << "Y Value" << endl;
	cout << "--------" << " " << "--------" << endl;

	a = slope(lownum,upnum);

	cout << a << endl;
}

float slope(float &x, float &y)
{	
	if(x<0)
	{
		y = x * (-1);
	}

	else if(x>=0 || x<=2)
	{
		y = sqrt(x);
	}

	else if(x>2)
	{
		y = 4;
	}

	return(x,y);
}
So can anyone tell me how many fucntions should i create and what should i be thinking about when making this program? Because i have a problem of how the program will work in my mind. Its not organized in my mind but all jumbled, which makes it hard to get it down to paper.