The main() Function

Your main() function should declare variables to represent the values of all the relevant quantities. Think carefully about naming these variables - note, for example, that variable names cannot involve subscripts, or greek characters. Think carefully about the type of each variable: is it to be used to represent a numerical value? If so, will that value be strictly integral, or may it have a fractional part?

The overall structure of your main() function will consist of some initialisation (assigning initial values to appropriate variables), followed by a while loop which carries out the repeated calculations of the new and co-ordinate values. This loop should continue just so long as the value is greater than zero. The repetition, or iteration, in your program should be achieved using a while statement.

It might be a good idea to start off with a highly simplified version of the main() function, having only a variable to represent and which just (for example) decrements the value by a fixed amount each iteration. This would allow you to check, at this early stage, that you have correctly implemented the while loop and that it terminates when appropriate.