Preprocessors

C Preprocessors are the header of the file

  • contains C function declarations and macro definitions to be shared between several source files.
    • In essence, they are like importing modules.
  • ex. stdio.h – Defines core input and output functions
  • In C, all lines that start with # are processed by preprocessor which is a program invoked by the compiler
    • a preprocessor takes a C program and produces another C program without any #
  • When we use include directive, the contents of included header file (after preprocessing) are copied to the current file.
    • < and > instruct the preprocessor to look in the standard folder
    • and instruct the preprocessor to look into the current folder
  • When we use define for a constant, the preprocessor produces a C program where the defined constant is searched and matching tokens are replaced with the given expression
    • ex. #define max 100max is searched for in the program, and is replaced with 100