User`s manual

The DOS contains commands for reading and writing directly to any track

and sector on the diskette. There are also commands for checking to see which

blocks (tracks & sectors) are available, and for marking off used blocks.

These commands are transmitted through the command channel

(channe[# 15), and tell the disk what to do with the data. The data must be read

later through one of the open data channels.

Opening a Data Channel for Random Access

When working with random access files,you need to have 2 channels open

to the disk: one for the commands, and the other for the data. The command

channel is OPENed to channel 15, just like other disk commands you've

encountered so far. The data channel for random access files is OPENed by

selecting the pound sign (#) as the file name.

FORMAT FOR OPENSTATEMENTFORRANDOMACCESSDATA:

OPEN file#, device#, channel#, "#"

or optionally

OPEN file#, device#, channel#, "# buffer#"

EXAMPLES OF OPENING RANDOM ACCESS DATA CHANNEL:

OPEN 5, 8, 5, "#" DON'T CARE WHICH BUFFER

OPENA.B.C,"#~

BLOCK-READ

FORMAT FOR BLOCK-READ COMMAND:

PRINT# file#, "BLOCK-READ:" channel, drive, track, block

or abbreviatedas .

PRINT# file#, "B-R:" channel, drive, track, block

This command will move one block of data from the diskette into the

selected channel. Once this operation has been performed, the INPUT# and

GET# statements can read the information.

TRACK NUMBER SECTORRANGE

TOTAL SECTORS

I to [7

o to 20

18 to 24 o to 18

25 to 30

o to 17 18

31 to 35

o to 16