Commodore 8-Bit Diskette Basics

By Larry Anderson larry@portcommodore.com

To send a command to the disk, you have to open a command channel, send the command then close the channel. In BASIC it would look like this:

OPEN 15,8,15,"(command)":CLOSE 15

(command) stands for the disk command that you need to execute.

If you are using a disk utility such as a wedge or fastloader, the command are sent easier by typing:

@(command) or >(command)

Below describe the various commands, keep in mind that you have to add the statemets above with the commands in order to send the command to the disk drive.

To set up a new diskette so you can write to it is called formatting. What the format does is writes a map on the disk for the disk drive to store, keep track of, and retrieve data. The command to format a disk is:

N0:(name),(id)

(name) is a 16 character name for the disk, its only purpose is for notation, when you view the directory this will be the first line.

(id) is a two character identifier, using any numbers or letters. This one's VERY important. Whenever you place a disk in the drive, the computer checks the disk's id with the previous disks, if they are the same it assumes the same disk is in the drive, and can cause problems when writing data to another disk with the same ID. If the disk has been previously formatted, you can omit the command id, to speed up re-formatting.

Sometimes, you may need to initialize or reset the disk drive, such as when a copy-protected program sets your disk drive off-track and other disks wont read, or when you have to use another disk that has the same ID. The initialize command is:

I0

If after issuing the command the drive light blinks, either there is no disk in the drive or there is a problem with the disk in the drive, or the disk has not yet been formatted.

If you use a disk constantly and write, erase, and re-write files, after awhile the disk needs to be checked in order to see if everything is accounted for, to do this you validate a disk. Also if for some reason a file appears on your directory with an * near the file type it has to be validated to remove the file properly. The validate command is:

V0

The command takes a while to run, as it checks each file on the disk. If the disk is a protected commercial disk or a GEOS disk DO NOT validate the disk unless the software manual says it's ok! Sometimes data can be lost on commercial disks.

In order to erase or scratch a file you have to send the disk a scratch command:

S0:(file name)

(file name) is the name of the file you want to remove, exactly as it appears in the directory. This command can scratch more than one file by using wildcards and/or by separating each file name with a comma.

To change the name of a file, you issue a re-name command:

R0:(new name)=(old name)

(new name) is the name you want the file to be, and (old name) is how it currently appears in the directory.

To read in a directory on the 64, there are two ways, one if you have no fastloader or wedge utility present. The first and main way is to load the directory as if it were a program, to do this enter:

LOAD"$",8

The dollar sign is the special name the disk drive gives its directory. After loading the directory you view it by entering:

LIST

If the directory is larger than the screen you can slow the scrolling down by holding down the CTRL key or stopping it by pressing the RUN/STOP key.

The main problem with this method is it overwrites any program currently in memory, so if you were looking for a disk with room, look for it before entering the program.

If you have a wedge or fastloader this command may work:

$ or @$

The benefit with this method is that the fastloader prevents the directory from wiping out your program. On some fastloaders and wedges you can use the space bar to suspend the listing of the directory, and pressing it again resumes the listing.

To send the directory to the printer, first you have to use the first method of getting the directory, by loading it into memory:

LOAD"$",8

Next the printer must be on and ready, once so, enter this command:

OPEN 4,4:CMD 4:LIST

if you wish the directory to be in upper & lower case enter this instead:

OPEN 4,4,7:CMD 4:LIST

The directory should list out onto your paper, after it finishes you must type one more command to finish:

PRINT#4:CLOSE 4

Remember this process will wipe out any program in memory, so make sure your program (if any) is safely SAVEd on a disk.

Lets look at a sample directory:

    .*0 "JOE'S GAMES     " 01 2A!
      33 "PACGUY"            PRG
      1  "TIC-TAC-BOOT"      PRG
      44 "3-D TIC-TAC-TOE"   PRG
      5  "TIC-TAC-DOX"       SEQ
      2  "HI SCORES"         REL
      89 "LEVELS"            USR
      490 BLOCKS FREE.

The top line is the title that was given to the disk during the format procedure, also on that line is the ID given to it as well as the format version (don't worry about that now).

The next 6 lines are the files contained on the diskette going across each line are the file size (in blocks), the file name, and the file type.

The bottom line is the number of unused blocks on the disk.

Files are data on a disk, sometimes they are programs. All files are recorded in chunks of 254 characters, these are called blocks. a 2 character file will use 254 characters or 1 block. a 265 character file, 2 blocks, and so on. A computer picture takes about 40 blocks. There are six file types, two of which do not appear on the directory:

These are files that have been scratched or removed during validation. They are tagged deleted so they can be overwritten when another file is added to the disk. Deleted files are in the directory, but are not displayed by the disk drive.

For the most part these are data files to be read by other programs, sometimes containing text (as this sequential file you are reading now).

Program files can be many things, BASIC programs, recordings of an area of memory, a picture file or some data used by another program. Some programs such as the first one are complete in one file while others like the second one use several files. Usually the first file in the set is the one that loads or 'boots' the program.

This is a datafile that is divided into equal sized chunks or records, and can be accessed at different points by a record number. Relative files are used primarily for database applications. These are by far the hardest files to copy, and you must use a special copier to move them from disk to disk.

This could be anything, from text to a special file structure (as in GEOS's USR file), user stands for user defined, almost always used by a specific program.

This type of file is not listed on the directory, it is data recorded directly to areas of the disk, bypassing the directory. Validating a disk can cause problems to these files. Commercial programs use random files a lot.

When loading and scratching files and reading directories there are special symbols you can use to locate a file or groups of files faster, they are called wildcards. Wildcards are the characters ?, *, and =:

This wild card can be used in place of a character it stands for any character. Let's say you have a file called POINTS, being a not so hot typist you could have named it PIONTS, so by calling it P??NTS you should find the file easier. this can also be used to locate say all 5 character files by using:

LOAD"$?????",8.

This is a cutoff indicator, say you name a file MISCALLANY but you don't want to type that all the time so you enter LOAD“MISC*”,8 and the disk drive will look for the first file that starts with MISC. You can use it in a directory to look for all the files that include something. Such as pictures that start with GG you can enter LOAD“$GG*”,8 and get ony the files starting with GG in the directory. This can be combined with the ? wildcard as well as a comma to add other conditions.

This one is one of those tricks you find by accident. This one will allow you to locate a certain 'type' of file. it has to be used with one of the above wildcards and a letter as well. An example would be, to list all sequential files on a disk enter: LOAD“$*=S”,8 and the directory will list ALL files that are sequential (if any). The different letters are:

• S = SEQ
• P = PRG
• R = REL
• U = USR
• (There seems to be no easy way of looking at DEL files…)

Wildcards are not allowed when renaming or saving files.

There are some who need clarification on loading and saving programs, also there are some things that may have been told to you that are no-nos now.

If you wish to initialize a disk before loading/saving a file put a 0: (example LOAD“0:PACGUY”,8) before the name of the file and the disk drive will run the initialize routine then load/save your file. Sometimes when my drive gets too hot I have to use it in order to get the drive to save my programs.

To load a file you type:

LOAD"(file name)",8  or LOAD"(file name)",8,1

(file name) is the name of the file, which can include wildcards. The ,8 tells the computer to access device # 8 for the function, Device 8 is the disk drive. If you have two drives, usually the second one is device # 9. When you just the ,8 the computer treats the file as if it were a BASIC program, by loading it to the start of the BASIC program memory, regardless of where it may need to go. If you cannot get the program to operate by loading it that way try ,8,1. ,8,1 lets the computer load the program into the same place it was recorded from. Sometimes there are special programs that start up the main program and need to be loaded by ,8,1. If both methods do not work, it may be that the file you were trying to load is data for another program file. If you are sure it is a runnable file, have someone with more disk knowledge look at it.

Saving BASIC programs are a breeze, all there is to it is to type:

SAVE"(program name)",8

Where (program name) is the name of the program up to 16 characters and contains no , “ ? * or :s, no ,1s are needed either. Though there is one thing you MUST NOT do, and that is the save with replace. Saving and replacing a file (example SAVE”@(file name)“,8) has a bug in most of the 1541 drives and can cause other files to be lost. If you wish to save a file with the same name as a previous file do this:

OPEN 15,8,15,"S0:(file name)":CLOSE 15  (scratch the old one)
SAVE"(file name)",8 (save the new one)

I call it Scratch & Save, and it's easier to remember that way…

Well that's the basics, anything else would require special programs, and a bit more knowledge in the workings of the computer & disk drive. Hope this helps you folks out.