Thread: learning to use #define

Hi

My elementary programming skills which I acquired not long ago are very much rusty these days. I was practicing with the code below but I received those two errors about the line at #17 in the source code. Would you please help me?

I remember when I started posting here people would tell me that my code isn't properly organized, like braces are not aligned etc. They used to use a certain term. What is it? Please tell me. Thank you for all the help.

Code:

//define_pi.cpp
// learning to use #define on Pi

#include <iostream>
#include <cstdlib>
#include <cmath>

using namespace std;

int main()
{
    float r, area;
    #define pi = 3.142;

    cout << "enter radius"; cin >> r;

    area = 2*pi*r;

    cout << "area is: " << area << endl;

    system("pause");
    return 0;
}

Errors:

Code:

17|error: expected primary-expression before '=' token|
17|error: invalid type argument of 'unary *'|