From: Daniel Barker <sokal AT holyrood DOT ed DOT ac DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: shifting left, and shifting right...
Date: Wed, 21 Jul 1999 10:53:40 +0100
Organization: Edinburgh University
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Pavlos wrote:

[good explanation of bitwise operations snipped]

I'd just like to add three warnings.

(1) Do not right shift a variable of a signed type. The result is
implementation-defined in C if the variable has a negative value.

(2) With an n-bit quantity, do not shift by more than n-1. e.g., do not
shift athe value of a 32-bit type more than 31, either to left or right.
The result is undefined in C.

(3) Do not attempt to shift by a negative number of bits. The result is
undefined in C.

Source: Kernighan & Ritchie, 2nd edition, Section A7.8; see also Section
2.9.

-- 
Daniel Barker.