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INPUT/OUTPUT FUNCTIONS
25.3 -- Device Independent I/O Functions
FMT
File -Format
o
User-defined -Format.
valid
for
diskette
This
-Format
is
only
files.
The record
I/O
functions cannot be used to access files with
t his
forma t.
On
1
y
log
i c
a
I
sec t or
I /0
can
b e
performed
with
this
-Format.
The
calling
program
is
responsible
for extracting data
from
the
sectors
according
to
his
data
struc ture.
1
Use
device's
default
format
Tor
binary
records.
Each device has associated with its
CDS (section 26.2)
a
flag that indicates
~hat
the default binary record format
is
(either
FMT
=
3 or FMT
=
7).
Since some devices can
only
process
seven-bit
data
while
other
devices
can
process
both
seven-bit
and
eight-b it data,
th is -Format
(FMT
=
1)
allows
a
program
to process binary records without
knowing the specific format
supported
by
a
particular
device.
The program will
alwa~s
be dealing with
eight-bit
data
in
memory.
The
FMT
field
is
automatically changed to
either
a
"3"
or
"7"
depending on
the
device
by
the .
OPEN
function.
2
Memory-image
format.
This
format
applies
only
to
diskette
files.
Any
f~le
whose
contents
are
to
be
loaded
into
memory
directly Trom the diskette
must
be
in
the
memory-image
format.
Due
to the nature of
the diskette controller, memory-image
format
files
must
be allocated contiguous diskette
space
(C = 1
or
IOCFDFL
Memory-image
riles
have
no
record
information within the data
sectors.
All
information
concerning
the
starting
load
address,
number
or
bytes to
load, etc.
I
is contained in the
rile's
RIB.
The load information must be written into the
RIB
by
the
program
that
is
creating
the
memory-image
filei
the
information
is not
automatically
supplied
by
any
system
function.
The load information must meet the
requirements defined in
section
24.2.
The
~ecord
I/O functions cannot be used to access
files with this format.
Only logical
sector
I/O can be performed with this format.
Page
25-29
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