# Digital design

#### rds1975

Joined Aug 30, 2004
8
Hi

Can somebody help me in solving this problem ?

Express the negative value 27 as a 2s complement integer using 8 bits. Repeat,
using 16 bits and 32 bits respectively. What does this illustrate with respect to the
properties of sign extension as they pertain to 2s complement representation.

Thanks and regards

#### Kingcosmos

Joined Sep 23, 2004
5
Originally posted by rds1975@Sep 21 2004, 12:56 AM
Hi

Can somebody help me in solving this problem ?

Express the negative value 27 as a 2s complement integer using 8 bits. Repeat,
using 16 bits and 32 bits respectively. What does this illustrate with respect to the
properties of sign extension as they pertain to 2s complement representation.

Thanks and regards
[post=2589]Quoted post[/post]​
It has been a while so let me see. In order to show -27 in 2's complement you need to write out +27 in binary (using 8 bits):

00011011

Then change all 0's to 1's and all 1's to zeroes:

11100100

11100100 + 1 = 11100101

Therefore 11100101 is -27 in 2's complement.

Repeat using 16 bits and 32 bits. As to the answer of your question I am not sure. I would answer it by saying that all negative numbers in binary have a 1 as a sign bit. :blink:

#### Liquid_Klone

Joined Sep 29, 2004
5
did you know that most scientific calculators show negative numbers in the 2s compliment? So if you are as lucky as I was, you can just type in -27, then hit your decimal to binary button, and the problem is solved. (I use texas instruments)