AVR-Chat

One huge huge hole with C in some microcontrollers is the loss of the status bits after a calculation.






----- Original Message ----
From: David Kelly <dkelly@hiwaay.net>
To: AVR-Chat@yahoogroups.com
Sent: Thursday, 28 February, 2008 3:42:06 PM
Subject: Re: [AVR-Chat] C problem

On Thu, Feb 28, 2008 at 08:13:49AM -0000, bhadson2001 wrote:
> 
> unsigned char a;
> a=255*20/10;
> 
> it gives output 254
> 
> for
> a=255*200/100;
> 
> it gives output 111
> 
> why it gives different results.
> 
> it there any logical relationship.

The intermediate math is signed 16 bit integer. 255*200 = 51,000 which
is -14,546. Divide by 100 = -145 = 111 unsigned.

-- 
David Kelly N4HHE, dkelly@HiWAAY. net
============ ========= ========= ========= ========= ========= ========= ======
Whom computers would destroy, they must first drive mad.




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