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LOAD COMMAND
18.
1 -
Use
additional
eight
bytes
of
memor~
beyond their
highest loaded address to allow room for a
stack
when
the
debug monitor is entered.
These eight
bytes must be within the contiguous memory
block
known to
MDOS.
If
either
of
these criteria is not met,
the standard error
message
will be
displa~ed
indicating that the program has
an
invalid load address.
ATter
the
program is loaded (without any options),
the
debug monitor will.
be
entered (as seen
by
the
input
pT'ompt
of
the
resident
monitor).
The
pseudo registers of the debug
monitor will have been initialized by the LOAD command to the
Following values:
Pseudo register Contents
?
X
S
A,B,C
Y
U=S
DP=Q
Starting execution
addr~ss
Lowest address loaded
into
Highest
address
loaded
into (eight
bytes greater than the highest actual
program location)
IndeteT'minate
Indeterminate (MDOS09)
MDOS09 only
MDOS09
only
Normally,
command-inteT'pT'eteT'-lo~dable
p~ogT'ams
take
advantage of the Tact that the stack pointer
is
initialized
to
the
end of the program area
by
using that part
of
memory
ror the actual stack during execution.
Such stacks must be a
minimum of 80 (decimal) bytes in size.
In addition to setting up the pseudo registers,
the LOAD
command will change the MDOS variable ENDUS$ (Chapter 24)
to
contain
the
last
address loaded into
by
the program.
This
allo~s
the
pT'ogram
to
dynamically
allocate
additional
contiguous
memoT'Y
ror
buffers,
etc.
I
via
the
".
ALUSM
u
function (Chapter 27).
Caution must be exercised when
loading
a
progT'am
and
entering
the debug monitor.
If MDOS is to be reinitializedl
the ABORT or RESTART
pushbuttons
must
first
be
dep~essed
before the debug command
!lEBOO; G
i i
aT'
;iMDOS:1
is
executed.
18.1.2
Non-command-interpreteT'-loadable progT'ams
P~ogT'ams
are
not
loadable
by
the
MDOS
command
interpreter must be loaded into
memo~y
ror either testing
or
execution via the
LOAD
command.
Normally,
such
p~ograms
will
overlay the resident operating system or will load into areas
Page
18-04
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