Splitting your C program

When you separate your C program into many files, keep these points in mind:

Be sure no two files have functions with the same name in it. The compiler will get confused.
Similarly, if you use global variables in your program, be sure no two files define the same global variables.
If you use global variables, be sure only one of the files defines them, and declare them in your .h as follows: extern int globalvar;
To use functions from another file, make a .h file with the function prototypes, and use #include to include those .h files within your .c files.
At least one of the files must have a main() function.

Note: When you define a variable, it looks like this: int globalvar;. When you declare a variable, it looks like this: extern int globalvar;. The main difference is that a variable definition creates the variable, while a declaration indicates that the variable is defined elsewhere. A definition implies a declaration.

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