Radio Shack TRS-80 Trsdos & Disk Basic Reference Manual page 91

DISK BASIC
Enhancements
to
LEVEL
II
BASIC
DISK BASIC
adds
many
features to
LEVEL
II
which
are
not
disk-
related.
They
are listed
below along with abbreviated
descriptions.
Detailed descriptions follow
in
alphabetical order.
&H
Hexadecimal-constant
prefix
&0
Octal-constant prefix
CMD"D"
Enable and
load the real-time
debugging
program
CMD"R"
Enable
interrupts
(start
real-time clock)
CMD"S"
Normal
return to
TRSDOS
(jump
to
EXIT
routine)
CMD'T"
Disable interrupts (turn off
real-time clock)
DEF FN
Define an
implicit
BASIC-statement
function
DEF USR
Define the entry point
for
an
external
machine-language routine
INSTR
Instring function;
find substring in target string
LINE INPUT
Input
a line
from keyboard
MID$=
Replace portion of
target string
(used
on
left
of equals
sign)
TIMES
Get
time and date
from
real-time clock
USRft
Call
external routine (n=0,
1,2,...
,9)
Cassette
Operations
Before any
BASIC
cassette
input or
output
operation,
you must
disable interrupts
with
the
CMD'T"
command.
This
is
because such
cassette
operations
are timing-sensitive
and cannot
work
if
they are
being interrupted every
25
milliseconds.
When
the cassette
operation
is
complete,
you
can
re-enable interrupts
by
executing the statement
CMD"R".
CLOAD
allows
no
filename
in
DISK
BASIC.
Tnerefore
you cannot
use
such
a
filename
to sort
through
several
tape
files.
CLOAD
will
always load the
first file
encountered on
the
tape.
CSAVE,
however,
still
requires the filename. This
way, programs
CSAVEd
under
DISK BASIC
can be loaded and
sorted
through
via
the
LEVEL
II
CLOAD"/z/e«ame" command.
CLOAD?
(CLOAD-verify), used
in
LEVEL
II
to
compare
a
BASIC
program
in
RAM
with
one on
tape,
will
not
work
with programs
saved
on
tape
under
LEVEL
II.
It
will
work
with
programs
saved
under
DISK
BASIC.
7-5