# EH-Net

## Ethical Hacking Discussions and Related Certifications => Other => Topic started by: ethicalhack3r on May 19, 2009, 05:44:28 AM

 Title: 2's complement help Post by: ethicalhack3r on May 19, 2009, 05:44:28 AM Hello,I had an exam this morning which had the following question:What is the largest positive value that can be represented using a 16-bit 2's complement representation?My answer was 32766Im sure its wrong tho, any one know the real answer? Title: Re: 2's complement help Post by: hayabusa on May 19, 2009, 09:21:21 AM Been a while since I've done this.  I think you're one shy, and the answer is 32767.16-bit would be 1000000000000000, and flipping the bits would yield 0111111111111111, which is equal to 32767 decimal.To support my thinking, I found the following:"For instance, a 16-bit word can represent signed integers in the range −32 768 to + 32 767."which I took from:http://openlearn.open.ac.uk/mod/resource/view.php?id=175771HTH.(edit - please excuse me if I'm incorrect, and someone tell us otherwise...  been a LONG time since I'd done these, too) Title: Re: 2's complement help Post by: ethicalhack3r on May 19, 2009, 12:39:53 PM I think your right because 0 is a positive number and I completely forgot about it.Thanks for the help!  :) Title: Re: 2's complement help Post by: jason on May 19, 2009, 05:50:37 PM What was the subject matter of the test, out of curiosity? Title: Re: 2's complement help Post by: ethicalhack3r on May 20, 2009, 06:11:14 AM Computer System FundamentalsThe whole module was based on the following book:Fundamentals of Computer Architecture - Mark Burrell (2004)http://www.amazon.co.uk/Fundamentals-Computer-Architecture-Mark-Burrell/dp/0333998669 Title: Re: 2's complement help Post by: Andrew Waite on May 20, 2009, 11:03:12 AM Ethicalhack3r,Quote from: ethicalhack3r on May 20, 2009, 06:11:14 AMThe whole module was based on the following book:Fundamentals of Computer Architecture - Mark Burrell (2004)Just out of interest, was Mark Burrell also one of the module lecturers?I remember some sleep-inducing lectures from him :DAndrew Title: Re: 2's complement help Post by: ethicalhack3r on May 20, 2009, 04:20:08 PM He wasnt one of my lecturers but he used to lecture at Northumbria, think he left a couple of years ago maybe?!I think its the logic gates that get me nodding off... Title: Re: 2's complement help Post by: Andrew Waite on May 21, 2009, 12:59:40 AM Must have left after my days then, tbh think the whole module got me sleeping. Wish I'd paid more attention now I'm playing with shellcode, turns out the low-level stuff is still relevant. Who'd of thought the lecturers would have a better understanding of the industry than the students? :) Powered by SMF 1.1.18 | SMF © 2013, Simple MachinesJoomla Bridge by JoomlaHacks.com