Radio Shack TRS-80 Model III - Page 132

TRS-80 MODEL
III
Functions
A function is
a built-in sequence
of operations which BASIC will
perform
on data.
A
function is
actually a subroutine
which usually returns
a data item.
BASIC
functions
save you from having
to write
a BASIC routine, and they
operate faster
than a BASIC
routine would.
A
function
consists of
a keyword which
is usually followed by
the data that
you
specify
.
This data is
always enclosed in
parentheses; if more than
one data
item is
required,
the items
are separated by
commas.
If the data
required is termed
'
'number' ' you
may insert any numerical
expression.
If it is
termed "string'
' you may insert
a string expression.
Examples:
SQR(A +
6)
Tells
BASIC
to
compute
the square
root of (A +
6).
MID$(A$,3,2)
Tells
BASIC to return
a substring
of the string
AS,
starting
with the third
character,
with
a length of
2.
Functions cannot
stand alone
in a
BASIC program.
Instead they
are used in
the
same way
you use expressions
—
as the
data in a
statement
.
For example
A
=
SQR
(7)
Assigns
A
the
data returned
as the
square root
of 7
.
PRINT
MID$(A$,3,2)
Prints the
substring
of
AS starting at the
third character
and two
characters
long.
If
the function
returns
numeric data,
it is
a numeric function
and may
be used in
a
numeric expression.
If it returns
string
data, it is a string
function
and may
be
used in
a string
expression.
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