Bitwise negation Post: 302117985

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Top Forums Shell Programming and Scripting Bitwise negation Post 302117985 by dLloydm on Thursday 17th of May 2007 01:37:45 PM

05-17-2007

Registered User

This has been very helpful. It reveals to me that UNIX is storing signed integer values just like most programming languages I am familiar with. The leading 1's for negative numbers would indicate that the highest order bit is a sign bit. Therefore 2#1010 is 10 and -2#1010 is -10 which would be represented as:
111....1110110 - depending on the bit size used.

Therefore I am suspecting the course is not correct when it claims ((~ 2#1001)) evaluates to 2#110, but that it actually evaluates to:
"-2#1010".

If UNIX used unsigned integers in this case then it would evaluate to a very large number depending on the bit size used. Something like 2#111...11110110. From your analysis I do not suspect this is the case.

There is one more thing I would like to verify. The course has the following question:
What do you think is the output of the following piece of code?
((x = 2#1101 & 2#110))
((y = ~x))
print - $y

The answer given is 11, as in decimal eleven or 2#1011.
From what I understand I think the answer should be -5 as in -2#101.

I plan to inform the course provider of these possible issues but I would like to make sure there is an issue. Thanks for your help.

dLloydm

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LEARN ABOUT OPENSOLARIS

macutil

MACUTIL(1)                                                    General Commands Manual                                                   MACUTIL(1)

NAME

       macutil - A package that deals with MacIntosh files on a Unix system

DESCRIPTION

       macutil  is  a package that contains a number of utilities that deal with MacIntosh files on a Unix system.  It contains the following pro-
       grams:

       binhex Convert files to BinHex 4.0 compatible hexified form.

       frommac
              Receives files from the MacIntosh on the Unix system.

       hexbin Convert hexified files to their MacIntosh format.

       macsave
              Save a series of files from a MacBinary stream as individual files.

       macstream
              Combine a series of files to a MacBinary stream.

       macunpack
              Unpack a MacIntosh archive into its constituents.

       tomac  Transmits files from the Unix system to a MacIntosh.

BUGS

       This manual page is hopelessly incomplete!

SEE ALSO

       binhex(1), frommac(1), hexbin(1), macsave(1), macstream(1), macunpack(1), tomac(1)

AUTHOR

       Dik T. Winter, CWI, Amsterdam, The Netherlands (dik@cwi.nl)

3rd Berkeley Distribution                                        October 22, 1992                                                       MACUTIL(1)