Path: utzoo!attcan!uunet!aplcen!uakari.primate.wisc.edu!zaphod.mps.ohio-state.edu!mips!sgi!shinobu!odin!dinkum!calvin
From: calvin@dinkum.sgi.com (Calvin H. Vu)
Newsgroups: comp.sys.sgi
Subject: Re: unsigned variables in f77 ???
Keywords: integer*1, unsigned, two's complement
Message-ID: <8809@odin.corp.sgi.com>
Date: 11 Jun 90 18:33:49 GMT
References: <6583@vax1.acs.udel.EDU>
Sender: news@odin.corp.sgi.com
Lines: 38

In article <6583@vax1.acs.udel.EDU> mccalpin@vax1.acs.udel.EDU (John D Mccalpin) writes:

>I am working with lots of 8-bit image data that I want to transfer
>rapidly to the screen using an f77 program.  Since RECTWR wants
>16-bit data, I have to copy the 8-bit data to a 16-bit array.
>Unfortunately, f77 considers the 8-bit (integer*1) data to be 
>signed, and so it does sign extension in the transfer to the
>integer*2 array.  Is there any clean way of turning this off?
>(Without coding in C!)

>Anybody have any better ideas?

    The intrinsic function ichar() returns an unsigned byte result so if
    you do short(ichar(char(byte(n,n)))) you will get what you need.
    This is my simple test case:

	byte a
	character b
	a = -5
	b = char(-5)
	print 10, a, b, short(a), short(ichar(b)), short(ichar(char(a)))
10	format(2(z2,1x), 3(z4,1x))
	end

and this is the result I got:
FB FB FFFB   FB   FB

Unfortunately, this only works in our latest release (3.3 release) so you
can only do this trick if you have the latest release.

>John D. McCalpin                               mccalpin@vax1.udel.edu
>Assistant Professor                            mccalpin@delocn.udel.edu
>College of Marine Studies, U. Del.             mccalpin@scri1.scri.fsu.edu

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