Question

Explain this hexadecimal subtraction

Answer 1

FFE,A7809-
13ABC,00000

Answer 2

Can't you write it more nicely? :P

Answer 3

FFE,A7809-
13ABC,00000
------------
?? 542,A7809

Answer 4

The two numbers are not equal in lengths?

Answer 5

@amistre64 @anwaarullah @eliassaab @tkhunny @undeadknight26 @Preetha @satellite73 @freckles @glamourglory @hartnn @Kamille @Loser66 @camerondoherty
And the answer is NO @waterineyes

Answer 6

\(FFEA7809\)
-\(13ABC00000\)
----------------

Answer 7

Last \(5\) digits will remain same..

Answer 8

@waterineyes you skipped the comma
those are not integer hex values

Answer 9

Then from the right, it is \(2\).

Answer 10

What does that "comma" signify?

Answer 11

hexadecimal point i suppose..

Answer 12

okay let's skip the comma
I'm interested only on this:
FFE-
13ABC
------

Answer 13

@ganeshie8 you're right

Answer 14

you want to work the subtraction in hexadecimal system without converting is it ?

Answer 15

yes

Answer 16

If we can find the 16's Compliment of 13ABC, then may be we can add them just simply.. :)

Answer 17

@waterineyes solve this exercise without using any Compliment
:D

Answer 18

Dear, I am here only, so still you feel need of tagging?? :P

Answer 19

Can't we switch the numbers by taking \(-\) sign out?

Answer 20

\(13ABC,00000\)
-\(FFE,A7809\)
-------------
-...................

Answer 21

13ABC
FFE
--------
12ABE

Answer 22

D??

Answer 23

\(12ABD\)

Answer 24

actually the answer is:
FFFFFFFFFFFED542

Answer 25

step1 :

1
13ABC
FFE
--------
E

1C - E = E

Answer 26

guys you're not helping me

Answer 27

you borrow a 16 from B and add it to units place C
then subtract..

Answer 28

ffe-13abc not reverse

Answer 29

i am trying to help you, how about you ? are u trying ?

Answer 30

No, firstly we will help ourselves then you... :P

Answer 31

how do you work 456 - 121314 in decimal ?

Answer 32

a-b = -(b-a) right ?

Answer 33

You think we are pearls here knowing everything.. :P Have patience..!!

Answer 34

since you don't want to use complements, there is no way to represent a negative number without using the minus sign

Answer 35

Yeah, ganesh I agree..!!

Answer 36

I'm here to figure out why:
00-
13
FFFFFFFFFFFED

Answer 37

I thought we're working on
```
okay let's skip the comma
I'm interested only on this:
FFE-
13ABC
```

?

Answer 38

0 0F FE
+
-------
1 3A BC

Answer 39

thats my idea

Answer 40

@ganeshie8 put 2 of 0 in front of ffe

Answer 41

ffe-abc=542
00-13=????????

Answer 42

filling 0's on left side is for machines, they are not needed for carrying out subtraction manually

Answer 43

00-13 = -13

Answer 44

http://www.csgnetwork.com/hexaddsubcalc.html

Answer 45

@ganeshie8 you mean this subtraction can't be done without using the compliment or the reverse code?

Answer 46

we should calculator now.. :P

Answer 47

how do you represent -13 on a machine ?

Answer 48

with the bit of sign

Answer 49

thats one way, and we call it signed magnitude system

Answer 50

however the one you're trying here is called 2's complement representation :

00-
13
FFFFFFFFFFFED

Answer 51

2's?? or 16's ??

Answer 52

...FFFFFFFFFFFED = 16's complement of 13

thnks for correcting water :)

Answer 53

you're using it to represent negative numbers without wasting a bit for sign

Answer 54

`00` - `13` = `00` + `(16's complement of 13)`

= `00` + `...FFFFED`

= `...FFFFED`

Answer 55

okay so if I'm right to find the 16's complement of -13 you do this:
FFFFFFFFFFFFF-
13
FFFFFFFFFFFED

Answer 56

yes subtract each digit from F and in the end add 1

Answer 57

YEAH THAT'S WHY F-3+1=D

Answer 58

thank you all for the patience

Answer 59

@Alexander95 this is cheating, you used Complements here.. :P

Answer 60

@waterineyes I can use complements I said that hoping I can find another way

Answer 61

But you limited my approach to "just subtracting" only.. :P It is fine.. :)

Answer 62

maybe take an example in base10 to see why the complement stuff works

Answer 63

base 10 :

`20` - `30` = `20` + `(10's complement of 30`)

= `20` + `70`

= `90`

Answer 64

you mean 100's compliment ? :P

Answer 65

Note that 10's complement of `90` is `10` as you expect the result to be...
the left most bit of 1 tells you that the stored number is negative

Answer 66

lol techically 100's complement is possible too as the base can be any real number

Answer 67

@ganeshie8 how many complements are:1's;2's;...;16's;...

Answer 68

there are only two useful complements in base N system :

1) N's complement
2) N-1 complement

Answer 69

and base can be anything,

11's compliment of 5 is 11-5

Answer 70

if you're in base 10, you call them 10's complement and 9's complement

Answer 71

so for base 2 we got:1,2
10 we got:9,10
..........
16 we got:16,15
.................

Answer 72

looks good, subtracting each digit by 9 or F may not reveal you much about whats going on.. there is a nice way to make sense of this complement business

Answer 73

\(10\)'s complement of a \(\large k \) digit number, \(\large x\), in base \(\large 10\) = \(\large 10^k-x\)

Answer 74

If you want to work the subtraction : \(\large w-x\) :
\[\large \begin{align} w - x &= w + (-x)\\&=w + (10^k-x)\\\end{align}\]

next, take the 10's complement of result, you get :
\(\large 10^k- \left[ w+(10^k-x)\right] = x-w \)

the computer adds a negative sign because it knows that the left most digit of the subtraction (w-x) is 1.