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SYSTEM DESCRIPTION
24.3 -- Record Structure
Symbol
Meaning
H
The FDR
heade~
character "H" ($48).
Be
A
one-bvte "byte count" that contains the
number of bytes in all fields
from
NAME
through
CK,
inclusive.
This number is
fixed for
FDR
records
at
17
(decimal).
This
number reflects the real data bytes
in the unconverted binary form,
not
the
bytes
written
in
the
ASClI-converted-binary form.
NAME
The eight-character file name.
SUrA
NU
~L_
.L...~
__
_
L
_ _ _ _
..L.. _ _ _ •• " . , . : .
.. _
I ne
ywu-~ndrc:H
.... t:'r
~urT"~
A.
A two-byte field which is not
used.
contains zeroes.
It
FDF
A two-byte field similar in format to the
attribute field
of
a
directory
entry.
Only
bits Sa-SA are used to describe the
f i
1
e
-Format.
CK
CR
The two Is-complemented sum
of
the
co·unt
and all other data bytes.
CK
one byte fielq.
The
terminating
carriage return}
character
sequence
line
feedl
and null.
byte
is a
of!
The length of all fields of the FDR (except Hand CR) is
doubled when written (ASCII-converted-binary Tormat).
Thusl
if
the
CR
field
is
counted as three characters (carriage
return,
line feed, null), then the physical length of an
FDR
in the ASClI-converted-binary format is 36 (decimal) bytes.
24.4 System Files
On
every
MDOS
diskette
there
are
nine
files which
comprise the
operating
system.
These
files
contain
the
resident operating system, a series of overlays to reduce the
main memory requirements of the system,
and
standard
error
messages.
The
resident
operating system file MDOS. SY must
reside in a f!ixed place on
the
diskette
if!
the
Bootblack
program
is
to
work
after
being activated by the diskette
controller.
The other system
files
must
remain
in
fixed
positions
after
MDOS
has
been
initialized since they are
re~erenced
by their physical sector numbers.
Page
24-15
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