Date: Thu, 18 Oct 2001 21:24:33 -0400
Message-Id: <200110190124.f9J1OXM05626@envy.delorie.com>
From: DJ Delorie <dj AT delorie DOT com>
To: djgpp AT delorie DOT com
In-reply-to: <9qnuii$kn8$1@tron.sci.fi> (traveler@netti.fi)
Subject: Re: Making C++ little easier to beginners...
References: <9qmkrh$581$1 AT tron DOT sci DOT fi> <9qmlmq$lou$1 AT News DOT Dal DOT Ca> <9qnuii$kn8$1 AT tron DOT sci DOT fi>
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> Please read a good Boolean algebra book to see that there really is
> no difference between "logical" AND/OR and "bit" AND/OR.

Except DJGPP doesn't compile good boolean algebra books, it compiles C
(well, and other languages).  In C, logical and bitwise operators are
different.

	0x52 && 0x1f => 1
	0x52 &  0x1f => 0x12

The difference is whether the individual bits of the value are handled
independently, or if the whole value is treated as a single boolean
(zero vs non-zero).  Try and see:

	int main()
	{
	  printf("&& %d\n", 0x52 && 0x1f);
	  printf("&  %d\n", 0x52 &  0x1f);
	  return 0;
	}

It's even more significant with certain pairs:

	0x0f && 0xf0 => 1
	0x0f &  0xf0 => 0