quick n easy question

This is a discussion on quick n easy question within the C Programming forums, part of the General Programming Boards category; why is the bold part of that line included? i understand 0 in ascii is nul, but don't know why ...

  1. #1
    Registered User
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    Nov 2005
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    quick n easy question

    why is the bold part of that line included? i understand 0 in ascii is nul, but don't know why it needs to be removed from the integer value that has been loaded into variable c

    Code:
    getnum(){
       int c, value;;
    
       value = 0;
       c = getchar();
       while(c != '\n'){
          value = 10*value + c - '0';
          c = getchar();
       }
       return (value);
    }

  2. #2
    Gawking at stupidity
    Join Date
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    Oregon, USA
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    i understand 0 in ascii is nul
    Be careful about this. '0' is not nul. '0' is 48 decimal in ASCII. '\0' is 0 (nul). But the program isn't using 0 (0), it's using '0' (48).

    '0' is useful when you have the character representation of an integer. Let's say you get input from a user and they type '5'. Well, if you want to use that as the integer 5 you have to do some math because '5' (in ASCII) is actually 53 decimal. So if you do '5' - '0' (which is 53 - 48) you get the integer value 5. By subtracting '0' from the ASCII character representation of a number you get that number's integer value.
    Last edited by itsme86; 11-10-2005 at 12:28 PM.
    If you understand what you're doing, you're not learning anything.

  3. #3
    Registered User
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    Nov 2005
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    perfect explanation. that helps in some other problems i was having...thank you ver much.

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