initializing array .

This is a discussion on initializing array . within the C Programming forums, part of the General Programming Boards category; Code: char arr[256]={'0'}; it puts '0' in every cell ??...

  1. #1
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    initializing array .

    Code:
    char arr[256]={'0'};
    it puts '0' in every cell
    ??

  2. #2
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    No. And I'm pretty sure we've talked about this before.

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  3. #3
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    i remember that we could put in every cell of an array one value
    by a similar way
    ??

  4. #4
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    Listen to matsp. You can find dozens of pages explaining this in google.

    PS: Really sure it's '0' and not 0?

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    Quote Originally Posted by transgalactic2 View Post
    i remember that we could put in every cell of an array one value
    by a similar way
    ??
    Only to the value zero (not '0', that's the character representing the digit zero, commonly the value 48, but not guaranteed). For any constant other then zero, you will have to either enter all the 256 values [16 rows of 16, for example], or write code to fill in the values - e.g. use memset().

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  6. #6
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    actually it was 0
    but i though it was '0' because its a array of chars

    not an array of integers

    ??

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    i cant put 0 into char array
    its a number
    ??

  8. #8
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    Quote Originally Posted by transgalactic2
    i cant put 0 into char array
    its a number
    Then you can't put '0' in a char array either, since it is also a number (of type int, in fact).
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  9. #9
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    the ascii value of 0 is NULL
    so it puts NULL in every cell

    and i can do this shortcut
    only with NULL value

    can i do
    Code:
    char arr[256]={67};//the letter that 67 represenst

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    Quote Originally Posted by laserlight View Post
    Then you can't put '0' in a char array either, since it is also a number (of type int, in fact).
    '0' is a char
    not a number

  11. #11
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    Quote Originally Posted by transgalactic2
    the ascii value of 0 is NULL
    so it puts NULL in every cell
    The null character has a value of 0, and this is true with ASCII as well. However, the macro NULL is different in meaning from the null character, even though they are equal and may have the exact same value and type. Consequently, it is usually semantically wrong to say that "it puts NULL in every cell" unless you are talking about an array of pointers.

    Quote Originally Posted by transgalactic2
    and i can do this shortcut
    only with NULL value
    This "trick" works with zero values, including NULL, because those elements of the array that are not explicitly initialised will then be zero initialised.

    Quote Originally Posted by transgalactic2
    can i do
    Yes, but you will end up with an array for which arr[0] has the value of 67 and the rest have the value of 0.

    EDIT:
    Quote Originally Posted by transgalactic2
    '0' is a char
    not a number
    No, '0' is an int, and the char type is an integer type.
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  12. #12
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    ya i just tested it works with
    Code:
    char arr[256]={67}
    but fills only arra[0] not all array other will be NULL

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    Code:
    char arr[256]={0};
    so if want to initialize arr without a loop
    i can put only NULL char in them

  14. #14
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    You could simply write out 67 256 times

    Or you could use memset().
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    Maybe even a for-loop, but memset is often more optimized. Or, if you don't mind a trailing NUL:

    Code:
    char arr[] = "00000000000000000000000000000000000000000000000"...;
    BTW: NULL is "(void *)0", NUL is "(char)0".

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