convert decimal numbers to excess-127 representations

Question

Represent the following decimal numbers in binary using 8-bit signed magnitude, one’s complement, two’s complement, and excess-127 representations.

a) 77

b) –42

c) 119

d) –107

I've converted them to the other representations just need to know how to convert to excess-127

a) Signed magnitude: 01001101 One's complement: 01001101 Two's complement: 01001101

b) Signed magnitude: 10101010 One's complement: 11010101 Two's complement: 11010110

c) Signed magnitude: 01110111 One's complement: 01110111 Two's complement: 01110111

please help

Welcome to stackoverflow. Your question does not make a lot of sense to me: What is input, what is output? What conversion method? Please add some more explanation to your post. — hotzst
Represent the following decimal numbers in binary using 8-bit signed magnitude, one’s complement, two’s complement, and excess-127 representations. a) 77 b) –42 c) 119 d) –107 as you can see i got all the other ones, just need help with excess-127 — Christine
Isn't excess-127 just adding 127 to the original number modulo 256, then just writing that as binary? en.wikipedia.org/wiki/Offset_binary — borancar

apratsunrthd apratsunrthd · Accepted Answer · 2017-09-12T12:41:22

It looks like you're doing exercise 16 from chapter 2 of The Essentials of Computer Organization and Architecture, 4th Edition. The text actually explains the concept quite simply in section 2.4.3, Excess-M Representation for Signed Numbers.

"The unsigned binary value for a signed integer using excess-M representation is determined simply by adding M to that integer."

So, for 77, you'd add M (127 in this case) to 77, giving you 204. COnvert that to binary and you get 11001100.

The rest should be easy to complete using the above method without asking the community to do your homework for you.

convert decimal numbers to excess-127 representations

2 Answers