Apple IIe - The System Monitor: Machine Language Interface; Introduction and Monitor Activation

CHAPTER
7.
THE
SYSTEM
MONITOR
Introduction
The
System Monitor
is
a set
of
machine
language
programs
bu
i
lt
into
the
Apple
lie.
The
System
Monitor
,
or
operat
i
ng
system, was
written
to
control
the
system
functions
of
the
Apple.
The system
functions
include:
•
monitoring
the
keyboard
and
peripherials
for
inputs
• displaying
output
on
the
screen
•
saving
and
retrieving
programs
from
cassette
•
controlling
the
speaker
•
allowing
the
user access
to
machine
language
The
operating
system's
programs
are used
by
high
level
lan-
guages such
as
Applesoft
and
Integer
BASIC.
The
Apple
Disk
Operating
System
also
uses
these
machine
language
programs.
Appendix
I lists
many
of
the
more
useful
machine
code
pro-
grams
as
well
as
their
starting locations.
These
programs
have
been
written
as
subroutines,
so
that
other
programs
may access
them.
The
remainder
of
this
chapter
will
focus
on
the
subset
of
pro-
grams
that
allows
the
user
direct
access
to
machine
language.
The
balance
of
the
chapter
assumes at least
a
rud
i
mentary
knowledge
of
6502
machine
language.
Activating and De-activating
the
Monitor
When
the
computer
is
powered-up
, a disk
boot
is
attempted
,
after
which
control
is
given
to
Applesoft
BASIC.
In
order
to
activate
the
Monitor
,
type: