Radio Shack TRS-80 Owner's Manual page 96

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FRS-80
MODEL
ill
DISK
SYSTEM
i^mms^*
Note
that positioning
to logical
record zero
sets the
file to
read the
first
logical
record
in
the
file.
To
position
to
end
of
file
in
order
to
add
new
records onto
the
end,
use
the record
number ern
+
1
Entry
Conditions
(DE)
=
dcb
(must
have been opened
previously)
bc
=
Logical record
number
to
position
for.
CALL SPOSN
Exit Conditions
Z
=
OK
a
=
trsdos
error code.
$READ^
17462/X'4436'
If
lrlo,
sread
transfers the logical
record
whose number
is
in the
dcb
as
nrn
into the
ram
area addressed
as
urec
for the length
lrl
as defined
at
open
time.
The
record
comes from "buffer"
defined
at
open
time.
If
trsdos must
read
a
new
physical record
to satisfy the request,
it
will
do
so.
"Spanned"
logical
records
will
be re-assembled
as necessary. $read
automatically Increments
nrn
by
1
in the
dcb
after
the transfer
is
completed. $init/open
set
nrn
=
x'oooo' in
order
to
read
the
first
record with
the
first
read.
If
lrl
=
o,
sread
transfers
one
physical record
into
buffer,
defined
at
open
time,
from
the
disk
file.
Registers
hl
are ignored.
$read
increments
nrn
as
above.
Entry Conditions
(HL)
=
urec
if
lrl
is
not
zero.
Unused
if
lrl
=
o.
(DE)
=
DCB
CALL SREAD
Exit Conditions
Z
=
OK
a
=
trsdos
error
code. (eof
=
x*ic
or
X'lD')
(see errors
28,29
for
eof
or nrf)
$WRTTE—
17465/X'4439'
If
lrlo,
swrite
transfers the
one
logical
record from
the
ram
area
addressed
as
urec
for the length
lrl
as
defined
at
open
time.
The
record
goes
into the
buffer which was
defined
at
open
time.
If
trsdos must
write a
physical record
80