IBM 1130 User Manual page 507

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ARITHMETIC CONSIDERATIONS

Of prime interest to commercial 1130 users is the

precision and accuracy of their arithmetic cal-

culations. Many engineering and scientific appli-

cations have very little need for answers with more

than five or six digits of accuracy. Much of the

input data comes from physical measurements (6. 34

pounds, 18.97 inches, etc.) that are only approximate

anyway, so the resulting answers (with some ex-

ceptions) must also be considered approximate.

However, in an accounting application,

$713,403.14 is exactlythat--$713,403.14.

add up your sales by area, by salesman, by item,

by customer, etc., the grand total for each had

better be the same, right down to the last penny.

For this reason, commercial programmers must

be familiar with the ways the 1130 does arithmetic,

and aware of their advantages and disadvantages.

For purposes of discussion, three are four ways

to do arithmetic on the 1130 system:

Integer mode

Real mode, floating point

Real mode, fixed point

Decimal mode

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