isdigit confusion

This is a discussion on isdigit confusion within the C Programming forums, part of the General Programming Boards category; Hi, According to documentation, isdigit returns a non-zero value is the value passed to it is a decimal integer, 0 ...

  1. #1
    Registered User Nutshell's Avatar
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    Jan 2002
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    isdigit confusion

    Hi,

    According to documentation, isdigit returns a non-zero value is the value passed to it is a decimal integer, 0 otherwise. BUt when i tested it in a simple program it does the opposite. Any ideas?
    Code:
    #include <stdio.h>
    #include <ctype.h>
    
    int main()
    {
       int c = 33;
    
       if ( isdigit( c ) == 0 )
          printf( "not an integer\n" );
    
       system("PAUSE");
       return 0;
    }

  2. #2
    ....
    Join Date
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    The definition of isdigit:

    7.4.1.5 The isdigit function

    Synopsis

    1 #include <ctype.h>
    int isdigit(int c);

    Description
    2 The isdigit function tests for any decimal-digit character (as defined in 5.2.1).
    So it is about decimal-digit characters.... and not about decimal values.

    isdigit (5) -> FALSE
    isdigit ('5') -> TRUE

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