Radio Shack TRS-80 model III Owner's Manual page 25

TRS-80 MODEL
III
DISK SYSTEM
How TRSDOS
Uses
RAM
trsdos
is
stored
on
the system
diskette
included with
your Disk System
Each
time
the Computer
is
turned on
or
reset, the
trsdos
master
program
is
loaded
into
ram
so
it
can
take charge.
trsdos
occupies approximately
40,000
bytes of
space on
the diskette;
however
only
a portion
of
that
is
in
ram
at
once. This
is
possible
because trsdos
is
'
divided
into several
independent
"modules."
The
"resident" module
is in
memory
at
all
times.
It
consists
of input/output
drivers,
tables,
the
command
interpreter,
and
other
essential routines.
Additional
modules
are
loaded
as needed, and
replaced
(or
"overlaid") bv
other
modules when
they
are
no
longer needed.
Note:
After you
enter a
library or
utility
command,
you
will usually
hear
trsdos
accessing
the system
disk.
It is
loading an
overlay module which
contains the code
necessary
to complete
the
command.
The Memory Map
in
Figure
8
illustrates
how
trsdos
utilizes
the available
memory
space.
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