Pointer to String

This is a discussion on Pointer to String within the C Programming forums, part of the General Programming Boards category; I'm getting started with c and i have the following question: Within main() Code: char string[] = "Hallo World"; function(string); ...

  1. #1
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    Pointer to String

    I'm getting started with c and i have the following question:

    Within main()
    Code:
    char string[] = "Hallo World";
    function(string);
    
    void function(char *str)
    {
        printf("%s\n",str);
        char *ptr = str + 5;
        *ptr = '-';
        printf("%s\n",str);
    }
    Output:
    Hallo World
    Hallo-World

    Why does the program doesn't work if i'm defining:
    char *string = "Hallo World";

  2. #2
    ZuK
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    Why does the program doesn't work if i'm defining:
    char *string = "Hallo World";
    This defines str as a string literal, a string constant. The copiler puts it into read only memory.
    Kurt

  3. #3
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    Thanks for the fast answer! But why the keyword "const" is not required? It seems that char* implicitly declares as const, same as const char[] ="Hallo World", and const char* = "Hello World" doesn't make sense then.

  4. #4
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by tinu73
    But why the keyword "const" is not required?
    Because there was a time where string literals existed but the const keyword did not, and the powers that be decided that allowing a string literal to be assigned to/to initialise a char* was the right choice, perhaps for backward compatibility.

    Quote Originally Posted by tinu73
    It seems that char* implicitly declares as const
    It doesn't.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  5. #5
    ZuK
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    I don't remember exactly. It's some backwards compatibility issue.
    Kurt

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