help needed
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  1. #1
    Join Date
    Mar 2013
    Posts
    11

    help needed

    what is the difference between unsigned char in[] and const unsigned char in[]

    Thanks

  2. #2
    2kaud's Avatar
    2kaud is offline Super Moderator Power Poster
    Join Date
    Dec 2012
    Location
    England
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    5,835

    Re: help needed

    const means that the data cannot be changed.

    Code:
    const unsigned char in[] = "qwerty";
    in contains the characters "qwerty" which cannot be changed.

    Code:
    unsigned char in[] = "qwerty";
    in again contains the characters "qwerty" but the characters in the array can be changed.

    Code:
    const unsigned char in[] = "qwerty";
    
    unsigned char in2[] = "qwerty";
    
    	in[0] = 'z';
    	in2[0] = 'z';
    In the above, the line highlighted produces a compile error as the code is trying to change the q to a z but in is defined as const so changes are not allowed. The in2 change is allowed as in2 is not defined as const.

    Hopes that helps.
    All advice is offered in good faith only. All my code is tested (unless stated explicitly otherwise) with the latest version of Microsoft Visual Studio (using the supported features of the latest standard) and is offered as examples only - not as production quality. I cannot offer advice regarding any other c/c++ compiler/IDE or incompatibilities with VS. You are ultimately responsible for the effects of your programs and the integrity of the machines they run on. Anything I post, code snippets, advice, etc is licensed as Public Domain https://creativecommons.org/publicdomain/zero/1.0/ and can be used without reference or acknowledgement. Also note that I only provide advice and guidance via the forums - and not via private messages!

    C++17 Compiler: Microsoft VS2017 (15.4.4)

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