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4.2
Constants
Numbers may be represented using either floating point or scientific
notation for positive and negative values. This BASIC has six decimal
digit accuracy and an approximate range of:
10E-38 to 10E38
0
-1OE-38 to -10E38
for positive numbers
zero
for negative numbers
A floating point number can be entered into the computer in the form
that you would normally write or type it. It may be a simple string of
decimal digits (an integer) or it may have a decimal point appearing
somewhere (a decimal digit). Since internal representation of numbers
in this form is only possible over a limited range, BASIC is forced to
convert very large or small numbers to scientific notation.
The form for Scientific Notation is to write the mantissa, follow it
by "E", and then the exponent. Any number over six digits long, whether
typed in by the user or generated by the program, will automatically be
converted to Scientific notation.
Expressions can also be used to represent numbers. The reasons for
using an expression can best be illustrated by an example.
Take for
instance the number 1/3. To type this into the computer as a decimal
digit requires seven key strokes for the most accurate representation
possible. You would type: ".333333".
An expression would have been
better here since only three keystrokes are required to type: "1/3".
They each represent the same quantity and typing in more than six 3's in
the first representation will not provide improved accuracy because
anything beyond six digits is ignored. Expressions are often desirable
just for the sake of clarity alone since not many people would
recognize: ".111111" as the fraction: "1/9". Some examples of different
number representations are:
floating point:
365
98.345
scientific notation:
6.02E-23
-1.145E7
numerical expressions:
22/7
7+1/6
(approximation for PI)
Another type of constant is the character string. It is different
than the other constants both in the way it is defined and in the way it
is usually used. Character string constants will probably be seen most
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