Radio Shack TRS-80 Owner's Manual page 34

m
TRS-80
MODEL
111
OISIC
SYS"
How TRSDOS
Uses
MAM
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") by
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.