Integer Limits (C++) Rosetta Code. Preprocessor directives. Preprocessor directives are lines included in the code of programs preceded by a hash sign (#).
These lines are not program statements but directives for the preprocessor. The preprocessor examines the code before actual compilation of code begins and resolves all these directives before any code is actually generated by regular statements. These preprocessor directives extend only across a single line of code. As soon as a newline character is found, the preprocessor directive is ends.