TECHNICAL INFORMATION
SPECIAL INPUT/OUTPUT
COMMANDS
BASIC offers two
special input/output commands.
These commands
input and
output data
directly
to
a particular
sector. They
do
this through
bypass-
ing the entire disk's
filing system.
The first, DSKI$, inputs the data from the sector
you specify. This
is its format:
DSKI$ drive number, track, sector, string vari-
ablel, string variable2
The first 128 bytes of the sector are input into
string variablel. The second 128 bytes are input
into string variable2. For example:
50 EXT$(0)
60
DSKI$
0,
17, 1
,
A*, B$ (ENTER)
inputs the contents of sector
1,
track 17 of
the disk
in drive 0. It inputs the first 128
bytes
into A$ and
the second 128 bytes into B$. After typing this
command,
you
can display the contents of
this sec-
tor with:
PRINT A$i B$ (ENTER)
Since DSKI$ will read any sector on the disk,
it is
the only BASIC command which will read
the
directory sector.
This
sample program uses DSKI$
to search the directory for filenames
with the
extension "DAT":
10 FOR X
=
3 TO 11
20 DSKI$ 0,17»X»A$»B$
30 C$
=
A$
+
LEFT$(B$»127)
40 NAH$(0)
=
LEFT$(C$,8)
=
MID*(C*,9,3)
TO 7
=
MID$(C*»N*32+1 ,8)
=
MID$(C$,9+N*32»3)
FOR N=l
70 NAM*(N)
80 EXT$(N)
90 NEXT N
100 FOR N=0 TO 7
110 IF EXT$(N)
=
"DAT" AND
LEFT*(NAM$(N) ,1)<>CHR$(0) THEN PRINT
NAM$(N)
120 NEXT N
130 NEXT X
The second command,
DSKO$, outputs data
directly
to
the sector
you
specify. Since it
bypasses
the disk
filing system, it will output data without
opening
a
file
and
listing
its location in the
direc-
tory. For this reason
you
need
to be
careful:
1. not
to output data over the directory sectors
unless
you
no longer plan
to
use the directory.
2. not to
output data
over other
data you
presently
have
stored on the disk.
The format of DSKO$ is:
DSKO$
drive number, track, sector, stringl,
string2
Stringl will
go in the first 128 bytes of the sector.
String2 will go in the next 128 bytes. For example:
DSKO* 0, 1. 3, "FIRST STRING", "SECOND
STRING"
(ENTER)
Outputs data to sector
3,
track
1,
on the disk in
drive 0. "FIRST STRING" will
go
in the first 128
bytes
of this sector. "SECOND STRING" will
go in
the second 128 bytes.
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