newbie: pointers to array question

This is a discussion on newbie: pointers to array question within the C Programming forums, part of the General Programming Boards category; hi im not really sure about this, hope u guys can help me understand. lets say we have a array ...

  1. #1
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    Wink newbie: pointers to array question

    hi im not really sure about this, hope u guys can help me understand.

    lets say we have a array of characters and a pointer:

    char string[] = "my string";
    char *p

    p = string +1;

    does this means dat p is now pointing to character 'y'?? if i dereference the pointer using *(p+2) it will point to a null value which is illegal cos p is only pointing to chracter 'y' and not the string itself?

    thanks for the help.

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    CSharpener vart's Avatar
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    p is pointint to the character y in the string
    so p+2 is pointing to string+3 to the character s and dereferencing it you will get the same char as string[3]
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    thanks vart., i understand it now. i have another question though. if i reference the array using &string[3], do i get character 's' as well?

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    no. you get the address of string, past three locations.

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    thanks manav for making this clear.

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    C++まいる!Cをこわせ! Elysia's Avatar
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    Note that pointers are only storing a memory location. So when you take the address of the string and add 1, you jump to the address one byte past the starting point. For strings, each character takes 1 byte, hence you jump to the second character, which is 'y', when you dereference the pointer.

    Now p is one byte past the start of the array. Add 2 more and you're 3 bytes past the start of the array. Dereference it and you get the 4th char, 's'. If you use the & operator, you take the address of something, so &string[3] gets the address where the 4th character is in the array (3 bytes past the beginning).

    Note that operator [] always deferences a pointer automatically, so string[3] gives 'y' and then & takes the address.

    For more information, an informative article might be,
    http://cpwiki.sf.net/A_pointer_on_pointers
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