Free Pascal Program Tutorial 15 - Procedures - Lazarus
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As your programs become more advanced, placing all the code in the main program can make the program more difficult to code. Slicing the program into sections can help. These sections are called by many names. The names include: subs, sub-modules, sub-procedures, and procedures. In pascal, these sections of code are called procedures.
The way that the procedures work, is that the main program, other procedure, or function will call the procedure. Once the procedure is called, the code within the procedure will run.