'_' character in .h files

This is a discussion on '_' character in .h files within the C++ Programming forums, part of the General Programming Boards category; Hi I am looking codes in header files for example when someone declare a header file (we say its names ...

  1. #1
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    '_' character in .h files

    Hi
    I am looking codes in header files
    for example when someone declare a header file (we say its names is MY_HEADER_FILE).
    then write in:
    Code:
    #ifndef MY_HEADER_FILE_H
    #define MY_HEADER_FILE_H
    Here why dont we write MY_HEADER_FILE.H instead of MY_HEADER_FILE_H.What is the purpose of using ' _'?

  2. #2
    Hardware Engineer
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    It's just convention.... Anything will work as long as you don't have the same #define statement in two different header files.

  3. #3
    vae victus! skorman00's Avatar
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    DougDbug is right, but you can't use a . in the preprocessor (the thing that handles #define)

  4. #4
    Cat without Hat CornedBee's Avatar
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    A macro name is not much different from other identifiers (class name, variable names, ...), so it is restricted to the same characters to make it up. These are alphanumeric characters and the underscore, and no number as the first character.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

  5. #5
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    thanks for answers.
    I asked this because i heard that c compiler write function names to the .obj file by put '_' character in front of function names.And c++ comp. put some character about its parameters.
    Here we put '_' instead of '.' in header files when defining a header.I wonder that is this a compiler specification? Or c++ specification?What is the rule of writing such a expression.

  6. #6
    Cat without Hat CornedBee's Avatar
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    Convention, mere convention. Since you can't use ., you have to use something else, and the only non-alphanumeric character available is _.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

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