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85
An expression is some combination
of
variables,
constants,
and operators which
can
be evaluated to a single
value.
The calculations
which you entered in Chapter 3 were
examples
of
expressions. Expressions
are an
intrinsi
c part
of
BASIC
programs.
For
example,
an expression might be a formula
that
computes
an
answer to some
equation, a
test to
determine the relationship
between two
quantities,
or
a means to
format a set of
strings.
-~
~
Expressions
(4) Variables subscripted
with
zero
(O) cannot
be
defined. I
f A(O) or A$(0) is
defined, an
error will result.
(5) When subscripts
greater
than A(27)
or
A$(27)
are first used, 7 bytes are used
for the variable
name,
and 8 bytes are used
for
each
variable.
defined at the same time as
they use
the same location in the
program/data area.
(3) Two dimensional arrays
cannot
be
defined, nor
is
it
possible to specify the
length
of character strings to be held in character array
variables.
For
example,
the
length of a character string
which
can
be
held in
character
array variable A$( ) is
limited to seven characters
or
less.
cannot be defined at the same
time.
Fer
example, P.~{30) and .ll.$(30) cannot
be
(2) Numeric array variables and
character array
variables with the same
subscript
--------------
A(30)
--------------
A(29)
BC
A(28)
A(27)
B(2)
B(1)
'-·-~J-~-
[Program/data
area]
If this program is
executed,
the
array
named
"A"
is not defined in two consecu-
tive segments in the
program
data
area, and an error
will
result at line 40.
Concepts
and Terms of BASIC
- Quick Links:
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