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__SUBTRACTION IN COMPUTERS__

__H__

__OW DO COMPUTERS SUBTRACT IN ANY EQUATION?__
Computer
is one of the best inventions in the whole world. Now in the era of electronics,
computers are shrinking in the size. The
dream of having pocket computers which was shown in many Hollywood as well as many film industry is
now a reality.

Many unimaginable discoveries and inventions are done with the
help of computers. As in this age the of
semiconductors and embedded systems we are achieving what was a dream, about
60-70 years ago.

Now
to achieve such a dream, the hard-work and dedication needed was given by many
scientists whose aim was to uplift the society.
Now if we want to invent something we need good hold on arithmetic computation. This computation was understood and logically
implemented by many scientists and engineers.

We
use Complements in digital computers for
almost simplifying the subtraction
operation and for logical manipulations and computations.

There are two types of complement for each
base-r system:

(1)
the r’s complement

(2)
the (r-1)’s complement

When
the value of the base is substituted, the two types receive the names 2’s and
1’s complementary for binary numbers, or 10’s and 9’s complement for decimal
numbers.

Now
let us see how this happens

__The r’s complement__
Given a positive number N in base r
with an integer part of n digits, the r’s complement of N is defined as r

^{n}_{ }– N for N#0 and 0 for N=0. The following numerical example will help clarify the definition.
The 10’s complement of (89654)

_{10}is 10^{5}- 89654 = 10346.
The number of digits in the number
is n = 5.

The 10’s complement of (0.9287)

_{10}is 1 - 0.9287 = 0.0713
No integer part 10

^{n}= 10^{0}is 1