How do you express negative numbers in hexadecimal?

Question

For exmaple how do you express -2 in hexadecimal in computer languages?

Answer 1

Considering a 8 bit register for 8 bits of the number including the sign bit (i.e storing 7 bits for the number and 1 bit for the signed).So we do 2's complement to -2 it becomes

+2 = 0000 0010
1111 1101 (1's comp)
+ 1
_____________
-2 = 1111 1110 (2's comp)

Convert this (11111110) binary to hexadecimal and you get hexadecimal value fe.

Therefore, -2 is (fe) in hexadecimal. So you can represent with - sign in programming language.And so -2 can be represented as , -0x2

8 bit register :- - 0x02 or 0xfe(hex)

16 bit register:- -0x0002 or 0xfffe(hex)

32 bit register:- -0x00000002 or 0xfffffffe(hex)

So the above is data represtation for -2 in 8,16,32 bit registers and in computer prgramming.

For x86 or x85 family of 8086 and 8085 micrprocessors of assembly Programming (low level language), we can directly declare -2 as databyte db like
.data
number db -2
.code
mov ax,number
mov ds,ax
or
mov ax,FEH
mov ds,ax

Hence all the ways of expressing -2.

Answer 2

You could make use of unary - and use -0x2. You could also do 0xfffffffe (32bit integer.)

Answer 3

Rory Zhao My gratitude and Thanks for marking my answer as best!!

Answer 4

You can just write it as -2. Hexadecimal and decimal are the same thing, it's just that hex has some more digits (ABCDEF). So -10 in dec would be -A in hex. The minus sign hasn't much to do with number bases.

If you are asking how computers store negative numbers that's a bit different. They use what's called two's complement; you have to dive into binary for that.* To get from say 10 to -10 you'd flip all the bits and add 1. So if you're on a machine with 8 bit wide numbers, here's an example:

0000 1010 bin == 10 dec
1111 0110 bin == -10 dec

So you could say -10 in dec is either -A in hex, which is always a correct way to say it, OR it is also F6 in hex on an 8-bit computer which uses two's complement numbers.
The way you can tell whether a number is negative on a computer is by looking at the leftmost bit. 0 is positive, 1 is negative.

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* You can group exactly 4 binary digits into 1 hexadecimal one.