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SYSTEM DESCRIPTION
24.3 -- Record
St~ucture
adding
the
bit mask X00110000 to the half-byte.
The result
is
a
displayable
two-byte
sequence.
For
example,
the
hexadecimal
data
byte
$85
would be converted into the two
byte sequence
$38
and $35.
24.3.4 File descriptor records
MDOS
I/Ooperations
~ith
non-diskette devices can
be
one
of
two
modes:
file
rormat
or non-file format.
non-file format
mode
requires
no special
processing and
on 1
y
th
eASe
I I rec o-' T "d format.
in
The
uses
The
rile
format
mode
allows
MDOS to
treat
the data on
certain non-diskette devices' as
a
ufilelll
similar to
a
-rile
on diskette.
The
File
Descripto~
R2cord
(FDR) is
employed
to
serve the same function as a directory entry ror
a
diskette
f i
1
e .
The
FDR
eon t a ins
a
.p
i
1 e
n a m e
j
S U
f
fix;
and a
r
i
1 e
format
descriptor.
Thus,
MDOS can search for a named file on
a
cassette
or paper tapel
if
i t
was originally created using
the file format mode.
All FDRs are identical
in
rormat,
regardless
oT
the
record
format
of
the
data
file.
Since
the FDR must be
acceptable
to
any
devicel
it
is
written
in
the
ASCII-conve~ted-binary
form,
even
if the remaining
data
of
the file is in binary or
ASCII. .
The FDR format is
shown
in
the following diagram:
: H : Be : NAME : SUFX : NU : FDF : NU : CK :
CR :
The symbols take on the following meanings:
Page
24-14
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