Path: utzoo!utgpu!water!watmath!clyde!rutgers!mit-eddie!uw-beaver!tikal!amc!pilchuck!dataio!bright
From: bright@Data-IO.COM (Walter Bright)
Newsgroups: comp.lang.c
Subject: Re: Simple question about:  ~
Message-ID: <1470@dataio.Data-IO.COM>
Date: 27 Jan 88 18:24:14 GMT
References: <1620006@hpcilzb.HP.COM>
Reply-To: bright@dataio.UUCP (Walter Bright)
Organization: Data I/O Corporation; Redmond, WA
Lines: 8

In article <1620006@hpcilzb.HP.COM> tedj@hpcilzb.HP.COM (Ted Johnson) writes:
<Could someone please explain why the following statements both give the
<same answer?
<	x = -y -1; vs. x = ~y;	

For a two's complement machine, the following identity is true:
	-y == ~y + 1
This property is frequently exploited in assembly language programs.