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SYSTEM DESCRIPTION
24. 5 -- Memory Map
Loc at ions
$OOOO-OOlF
I
inc
1 us i
ve,
are re served for
th
e
variables of
the
diskette controller.
These locations cannot
be
initialized
by
a program loading from the diskette.
In
addition,
if a program
requires
the
use
of
the
diskette
functions (either directly through the diskette controller or
through the MDOS functions)
I
then these locations
cannot
be
used
by
the
program
for
storage.
Locations
$OOAE-OOFD,
inclusive, contain the MDOS command line as
it was 2ntered
by
the
operator.
Command-interpreter-loadable
programs
must
load
above
location
$lFFF.
They
can
use
the
direct
addressing
area
for
variable
storage;
however:
this Cll'ea
cannot be initialized while the program is being loaded
into
memory.
Pl'ograms
that
do
not
make
use
of
MDOS system
functions can load anlJUlhere in memorl,J above
loca1;ion
$OOlF.
If
such
programs
do
not use the diskette controllel' entry
points
(Appendix
D);
the
direct
aaaressing
area
below
location
$0020
can
be
used,
but only after the program is
resident in memory.
The
MDOS
vari.ables (locations
$FE
and, highe-r)
contain
pointers to several areas in memory that might be required by
a user program.
The absolute
addresses
of
these
pointers
should
be
obtained Tram the MDOS equate file.
The pointers
most often required are:
Pointer Name
CBUFP$
ENDOS$
ENDUS$
ENDSY$
Content
The
address
in
the
command
line
buffer
to
the
terminator
or
the
command being
executed.
Parameters
following
the command name should be
scanned ror by using the contents
of
this variable.
The
address
of the last location of
resident MDOS.
The
value
Or
this
address
plus
one
is
the
fil'st
location
that
a
command-interpl'eter-loadable
program
can load into.
The
address
of
the
last
location
loaded
into
by the current program.
The
program can
allocate
additional
memo~~
(between
the
last
loaded
location and the
end
Or
contiguous
memol'Y)
via
one
of
the
system
functions.
The
address
of
the
last
byte
of
contiguous memory (RAM).
Page
24-19
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