Radio Shack TRS-80 Trsdos & Disk Basic Reference Manual page 172

Appendices
interrupt
A
signal
which
causes the
Computer
to interrupt whatever
it is
doing
and perform some
other
specified task;
when
the task
is
completed,
the
Computer
will
generally
resume
execution of
the previous
task.
The TRS-80
Expansion
Interface includes a
25
millisecond
"heartbeat"
interrupt,
which
is
used
to drive the real-time
clock
and
other foreground
tasks.
Interrupt-driven tasks can be scheduled and
assigned
priorities,
so that the
Computer
appears
to
be doing two
or
more
things "at
once".
kilobyte or
K
1024
bytes of
memory.
Thus
a 12
K ROM
includes
12*1024=12288
bytes.
library
commands
A
set
of overlayed
TRSDOS
commands
which
are overlayed
as
needed
into
RAM
between 5200
and
6FFF,
to see
which
library
commands
are available, use the
TRSDOS
LIB command:
LIB
<EN>
logical expression
An
expression
which
is
evaluated
as
either
True (=-1) or
FALSE
(=0).
logical record
A
block of data which
contains
from
1
to
256
bytes, and can be
addressed
as a unit,
regardless
of whether
the
logical
record
is
contained
in a single record or spans
two
physical records.
machine
language
The
Z-80
instruction
set,
usually specified
in
hexadecimal
code.
All
higher-level languages
must
be
translated into machine-language
in
order
to
be executed by
the
Computer.
null string
A
string
which
has
a
length of
zero;
For
example,
the assignment
A$
=
" "
makes
A$
a null-string.
object code
Machine
language derived from
"source code",
typically,
from
Assembly
Language.
8-8