It's a program that takes your source files as input, does some processing on it and outputs the processed sources. Then theese modified sources are compiled the normal way. The processor Michael Reitzenstein has done is working pretty much like the one that ships with C compilers: it allows to add special statement (the ones that start with a '#') that are understood by the preprocessor. For example you can make code that will be compiled only if a certain macro is defined (say DEBUG):
#IfDef DEBUG
blabla
#EndIf
Then "blabla" will stay in the final( preprocessed) source only if 'DEBUG' is defined. It's very useful to add consistency testes that makes debugging much easier, while letting you suppress these checks (which involves an ovehead by theirselves) when you are sure all works fine: you only need to undefine DEBUG for this.
You may want to just type something like "C preprocessor" in any search engine to find more info.
#IfDef DEBUG
blabla
#EndIf
Then "blabla" will stay in the final( preprocessed) source only if 'DEBUG' is defined. It's very useful to add consistency testes that makes debugging much easier, while letting you suppress these checks (which involves an ovehead by theirselves) when you are sure all works fine: you only need to undefine DEBUG for this.
You may want to just type something like "C preprocessor" in any search engine to find more info.