Page 286 - FUNDAMENTALS OF COMPUTER

NPP

286 Fundamentals of Computers NPP

Step 1: Represent in 8-bit ñQ>on 1… XmoZm| H$mo 8-{~Q>m| _| Xem©Zo na

(00001111) – (11101111)
Step 2: Take 2's complement of subtrahend: ñQ>on 2… KQ>H$ H$m 2's H$m°påßb_|Q> bmo…
00010001
Step 3: Replace (–) with (+) and add. ñQ>on 3: (-) Ho$ ñWmZ na (+) H$aHo$ Omo‹S>mo …

00001111 + 00010001 = 00100000
Since MSB is 0 the integer is positive and My±{H$ MSB eyÝ` h¡ AV… n[aUm_ YZmË_H$ h¡ d
the remaining bits show the magnitude. Thus, ~mH$s {~Q>| CgH$m n[a_mU ~VmVr h¡Ÿ& AV…

(+15) – (–17) = (+32)
We can draw flow chart for 2's complement AV… h_ 2's H$m°påßb_|Q> KQ>mZo H$s {d{Y H$m
subtraction (Signed Integers) âbmoMmQ>© ~Zm gH$Vo h¢:

Start

Represent
Positive Integer in signed-
magnitude form and
Negative in 2's complement 2's

's
Take 2's complement of
subtrahend. Replace
(-) with (+)

Add & Neglect any
end carry

Stop

Flow chart : 2's Complement Subtraction âbmo MmQ>©… 2's H$m°påßb_|Q> _| KQ>mZm (gmBÝS>
method (Signed Integers) nyUmªH$)
Problem 3.81 àíZ 3.81
Perform subtraction using 2's complement 2's H$m°påßb_|Q> go KQ>mAmo…
method :
(a) (+25) – (+25) (b) (+43) – (–20)