a small help here

This is a discussion on a small help here within the C Programming forums, part of the General Programming Boards category; hello guys, i had a little problem in understand the pointer to pointer reference concept (i.e **p) how it is ...

  1. #1
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    a small help here

    hello guys,
    i had a little problem in understand the pointer to pointer reference concept (i.e **p) how it is used. and what is the effect of uisng that.

    any help will be appreciated

  2. #2
    Handy Andy andyhunter's Avatar
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    Try reading through this post. It was discussed decently there. Let me know if you have any questions.
    i don't think most standard compilers support programmers with more than 4 red boxes - Misplaced

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  3. #3
    UT2004 Addict Kleid-0's Avatar
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    Think of **p as p[][]. A multidimensional array (even though technically it's not).

    Code:
    const char **p = {
        "Apples",
        "Cornbread"
    };
    
    // p[] would carry the strings
    // p[][] would carry the characters of the strings
    
    // *p would carry the strings
    // **p would carry the characters of the strings
    
    p[0][0] = 'B' // Change Apples to Bpples 
    **p = 'C'      // Change Bpples to Cpples

  4. #4
    and the hat of int overfl Salem's Avatar
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    Does any of that work?
    I very much doubt it.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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  5. #5
    ATH0 quzah's Avatar
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    You mean because of const, or because they're string literals. Or both.

    Quzah.
    Hope is the first step on the road to disappointment.

  6. #6
    UT2004 Addict Kleid-0's Avatar
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    This is crazy horse !

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    
    int main( void )
    {
       // Create a string array
       
       char p[2][100];
    
       // Copy the strings into the string array
    
       strncpy( p[0], "Apples", sizeof( *p ) );
       strncpy( p[1], "Corn Bread", sizeof( p[0] ) );
    
       // Next is the same thing as:
       // **p = 'B'
       
       p[0][0] = 'B'; // Change Apples to Bpples
       puts( p[0] );
    
       // Next is the same thing as:
       // p[1][5] = 'X'
       
       *( ( *( p+1 ) )+5 ) = 'X';      // Change Corn Bread to Corn Xread
       puts( p[1] );
    
       return 0;
    }

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