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From: wallis@labc.dec.com (Barry L. Wallis)
Newsgroups: comp.lang.c
Subject: Re: A Simple question
Summary: signed vs. unsigned chars
Message-ID: <1524@mountn.dec.com>
Date: 11 Apr 90 05:25:24 GMT
Sender: news@mountn.dec.com
Organization: Digital Equipment Corporation
Lines: 29


In article <1881@zipeecs.umich.edu>, yhe@zip.eecs.umich.edu (Youda He) writes...
!>Here is the sample program:
!>main()
!>{
!>  char a=255;
!>  unsigned char b = 255;
!>  printf("a=%X\n",a);
!>  printf("b=%X\n",b);
!>}
!> 
!>The result is 
!>a=FFFF
!>b=FF
!>on dos, by using zortech and mcs, char is 8 bit long, why a looks like 16bit?
!>what is the difference of char and unsigned char on printf? 
!> 
!>-- Youda

The %X specifier in printf() tells the function to interpret the argument as an
int. Since the actual value is a char it is pushed on the stack as an int. If
the value pushed is defined as a signed char (as 'a' is), the high order bit is
sign extended; otherwise the high order byte is 00.
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Barry L. Wallis			USENET: wallis@labc.dec.com
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