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58
Chapter 3
Data Representation
decimal system, a sign (+ or
±
) is placed before a number’s value, though
the positive sign is often assumed. The sign represents the ordering, and
the digits represent the magnitude of the number. The classic number line
looks something like this, in which a negative sign meant that the number
was to the left of zero and the positive number was to the right of zero.
Performing addition and subtraction with signed integer numbers can be
described as moving a certain number of units in one direction or another.
To add two numbers you find the first number on the scale and move in
the direction of the sign of the second as many units as specified. Subtrac
tion was done in a similar way, moving along the number line as dictated
by the sign and the operation. In grade school you soon graduated to
doing addition and subtraction without using the number line.
There is a problem with the signmagnitude representation: There are
two representations of zero. There is plus zero and minus zero. The idea of
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 Fall '10
 MARIANAKANT

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