How represent -128 in binary for a byte?

Question

In order to avoid representing 0 in two different ways when representing signed integers in bytes such as

10000000

and

00000000

one can say, by convention, that 10000000 = -128. Is this correct?

Yes, that's the twos complement representation. – Michael Liu Feb 01 '14 at 01:34 — Michael Liu, Feb 01 '14 at 01:34

score 1 · Answer 1 · answered Feb 01 '14 at 01:36

1

Yes, but not quite by convention - it is a formula. By the same formula -1 will be 11111111.

Read here for details http://en.wikipedia.org/wiki/Two%27s_complement

answered Feb 01 '14 at 01:36

Bogdan

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score 1 · Accepted Answer · edited May 23 '17 at 10:25

Obviously there are different possible representations, including the one you mentioned which has two different numbers for 0.

Two's complement is the only representation I know of that's used in computers, and for that one your assumption is correct. In the datatype sometimes known as signed char, binary 10000000 is indeed -128. See:

How represent -128 in binary for a byte?

2 Answers2