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SYSTEM DESCRIPTION
24.6 -- MDOS Command
Inte~prete~
(CBUFP$)
~as
leTt pointing to the terminator that stopped the
scan
for
the
first
valid file name specification when the
MDOS
command interpreter processed the input'
buffer.
After
completing
its
function,
the
command
can
return to MDOS
through one of the system functions C. MDENT) which
~ill
pass
control
back
to the MOOS command interpreter, repeating the
cycle.
It should be
noted
he~e
that commands
invoked
via
the
MOOS
command
interprete~
do not necessarily have to have the
suffix lIeM" or reside on drive
ze~o.
If a user program
with
an
IILO"
suffix is being tested,
it can be loaded. and executed
di~ectly
from the command line (if it meets
th~
requirements
for
command-interprete~-loadable
programs)
by
explicitly
entering the suffix after the file
name.
Similarly.t
if
a
required command does not
happen
to reside on drive zero,
its
name can be followed with a logical unit number to
cause
it
to
be
looked
for
and loaded from the specified unit.
For
examp Ie,
the command line
OIR:2
will invoke the directory command from drive
two
to
display
the directory of the diskette in drive zero,
Whenever
the
MDOS
command interpreter regains control
after a command terminates,
i t
checks that
the
diskette
in
drive
zero
still
has
the same parameters <version numberl
overlay RIB addresses) as the diskette used during
the
last
MOOS
initializa'tion.
If these parameters differ,
one of the
standard error messag es
EL
ER,
EU,
EV
(Chap ter
28)
wi
11'
be
displayed
and control given to the debug monitor.
MDOS will
then
have
to
be
reinitialized
before
the
MOOS
command
interpreter will accept
furthe~
commands.
In
addition;
the following parameters are reinitialized
each time the MDOS command
inter~reter
is given control.
The
user-defined
SWI
and
IRG
vectors
(SW!SUV and IRG$UV) are
reset to point to an RTI instruction.
(Only SWISUV is
reset
for
MDOS09.)
Since
the user program is no longer resident,
the interrupt handlers are deactivated.
The stack pointer is
reset to the end of contiguous memory for the duration of the
command
inte~preter's
execution.
The Error Status and
Error
Type parts of the system error status word are set or cleared
d
ep end i ng on
Ufh
eth er or not a va
1
i
d
command name. was
entered
on the command line.
24.7
Interrupt Handling
When
MDOS initializes,
it saves the contents of the SWI
v~ctor
required. by ... the
debug
monitor,
The
SWI
and
IRG
vectors
are
then
changed
to
point into the
MOOS
function
handler.
Both vectors are required to allow the operator
to
Page
24-21
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