Note
that
when key values for the SECOND joystick are returned, the computer
cannot tell whether those values have been generated by the joystick or by the
equivalent keyboard key (indicated
in
the
last
column of the previous table). This
means
that
the keyboard can be used as a substitute for
the
second joystick.
Part
12:
Disc organisation
The BIOS supports three different disc formats: SYSTEM format, DATA ONLY
format
and
IBM format. Under AMSDOS, the format of a disc is automatically
detected each time a disc
with
no open files is accessed.
To
permit this automatic
detection, each format
has
unique sector numbers.
3 inch discs
are
double sided,
but
only one side may be accessed
at
a time depending on
which way round
the
user inserts
the
disc. There may be a different format on each
side.
Common
to
all
formats:
Single sided (the two sides of a 3 inch disc
are
treated separately).
512 byte physical sector size.
40
tracks numbered 0 to 39.
1024 byte
CP/M
block size.
64
directory entries.
SYSTEM
format
9 sectors per
track
numbered
&41
to &49.
2 reserved tracks.
The system format is
the
main
format supported, since
CP/M
can only be loaded from
a system format disc.
CPIM
2.2 also requires a system format disc to be inserted for a
warm boot. The reserved tracks
are
used as follows:
Track
0 sector
&41
Track 0 sector &42
Track
0 sectors &43 to
&47
Track 0 sectors &48 to
&49
Track 1 sectors
&41
to &49
CP/M2.2
CP/MPlus
: boot sector for
CP!M
2.2 : boot sector for CP
IM
PI us
: configuration sector
: unused
~
} CCP and
BD
OS
} unused
Note
that
VENDOR format is a special version of system format which does not
contain any system software on
the
two reserved tracks.
It
is intended for use in
software distribution.
Chapter 7
Page
44
For your reference
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