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SYSTEM DESCRIPTION
24. 1 -- Diskette Structure
map
of
which areas of the diskette have been flagged
as bad
-~
during the
DOSGEN
write/read test.
In additionJ
the
LCAT
is
)
configured
so that those sectors or the diskette occupied
by
the system tables in cylinder zero and any
user
lo~ked
out
areas
(see
Chapter
10,
DOSGEN
command)
are
flagged
as
unavailable ror normal allocation.
24. 1. 4 Directory
The
director~
occupies twenty sectors.
Each
directory
sector
contains
eight
entries
Or
sixteen bytes each.
Each
entry contains a rile name, a
suffix,
the
address
of
the
file's
first
clusterl
the file's attributes, and some room
for e x pans ion.
A
rile
is
one
or
more
clusters
containing
related
information.
This information may be ASCII source programsi
binary object records,
user-generated data,
etc.
Each
-rile
must
reside
wholly
on
a
single
diskette.
Files
are
identiried to
the
system
by
their
names,
suffixes,
and
logical unit numbers.
The
name
as
stored
in
the directory consists
or
ten
bytes;
howeve~
the MOOS command
interpreter
deals
with
an
eight-byte
name. and
a
two-byte
suffix.
This is merely a
c~nvention
of the command
interpret~r
and
has
no signi-ricance
in
relatirin to the internal format of the directory.
System
routines and functions dealing with file names as a
pa~ameter
use
a
ten'-b'Jte
block
which ..
is
always
dealt
w-ith
as a
mon
01
i t hie item.
File names assigned by the user
must
be
from
one
to
eight alphanumeric characters in length.
The first character
must be alphabetic.
A
file's
suffix
is
used
to
further
identify
the file.
The suffix is primarily used to identify
the for ma t
0
f the f
i 1
e
con
t
e"
t
i
h
0
us
eve r
I
t
n
i
s i s
pur e
1 tl
a
convention;
the
attribute
field
of
the
director~
entry
describes
the
file's
physical
format.
Suffixes
are
considered as an extension
of
the file name.
They can be one
or
two
alphanumeric
characters
in
length.
The
first
character
of
the
suffix must be alphabetic.
Both the file
name and the suffix,
if
shorter than their maximum
allowable-
lengthsl are left Justified and space-filled in the directory
entry.
In most cases, the MDOS commands
make
certain
default
assumptions
about
a
file's
suffix if it is not explicitly
specified
by
the operator;
however, explicit suffixes can
be
used
whenever the derault is to be overridden.
The standard
MDOS.default suffixes
ar~:
\
. .,J
Page
24-04
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