Commodore VIC 1541 User Manual

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COMPUTER

VIC-1541

SINGLE DRIVE FLOPPY DISK

USER'S MANUAL

P/N 1540031-02

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COMPUTER

WARNING: This equipment has been certified to comply with the limits for I!, Class B computing device, pursuant to Subpart J of Part 15 of FCC Rules. Only computers certified to comply with the Class B limits may be attached to this printer. Operation with noncertified computers is likely to result in interference to radio and TV reception,"

This warning is valid for the equipment which has the following FCC label on its rear.

CERTIFIED TO COMPLY WITH CLASS B LIMITS. PART 15 OF FCC RULES SEE INSTRUCTIONS IF INTERFERENCE TO RADIO RECEPTION IS SUS-

PECTED.

The information in this manual has been reviewed and isbelievedto be entirely reliable. No responsibility, however, is assumed for inaccuracies. The material in this manual is for information purposes only, and is subject to change without

lIotice.

@Commodore BusinessMachines, Inc., September 1981

Table of Contents

Page

General Description

Unpacking and Connecting .

Contents of Box . . ..

Connection of Cables

PoweringOn ........

Insertion of I)jskette . .. . .

Usingwith VlC 20 or Commodore 64 .

UsingPrograms..............

Loading Pre-packaged Software

LOAD .

Directoryof Disk .. .. .. .. .

Pattern Matching & Wild Cards

SAVE .

SAVE and replace. . .

VERIFY.. .. . .. ..

DOS Support Program

4. Disk Commands . . . . . . . .

OPEN ANDPRINT #

NEW ...

COpy.. ..

RENAME. SCRATCH INITIALIZE VAUDATE.

DUPUCATE

Reading the Error Channel CLOSE

.. .. . .. . .. .. .

..............

3 6

6 7 7 8

8 9

9 9

9 11 12 13 13 14

14 14

17 17 18 18 18

SequentialFiles . . . . . . . . .

OPEN .

PRINT # and INPUT #

GET# ..

Reading the Directory

RandomFiles ..........

Opening a channel for random accessdata

BLOCK-READ. . . . .

BLOCK-WRITE . . . .

BLOCK-ALLOCATE.

BLOCK-FREE . . . .

BUFFER-POINTER USER 1 and USER2

19 19 20 22

27 28 29 29

7. RelativeFiles. .. ... .. .. . ... . . .. ., . 33

Creating arelative fde .. .. .. . .. .. . 34

Usingrelativefdes.. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3S

8. Programming the Disk Controller. 37 BLOCK-EXECUTE 37

MEMORY-READ.. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 37

MEMORY-WRITE 38

MEMORY-EXECUTE . . . . . . . . . . . . . . . . . . . . . . . . . . ..

USERCommands 39

9. Changingthe Disk Device Number .. . . .. . . . .. . . .. . . .. . . ... 39

Software Method .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 39

HardwareMethod 40

Appendices

A. DiskCommandSummary. 41

B. ErrorMessages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 42

C. Demonstration Disk Programs

D. DiskFormatsTables .. . . . . . . . . . . . .. . . . . . . . . . . . . .. S4

. . .. . . . . . . .. . . .. . . .. . .. 47

1. GENERAL DESCRIPTION

Introduction

Welcome to .the fastest, easiest, and most efficient filing system available for your Commodore 64 or VIC 20 computer, your 1541 DISK DRIVE. This manual has been designed to show you how to get the most from your drive, whether you're a beginner or an advanced professional.

If you are a beginner, the first few chapters will help you through the

basics of disk drive installation and operation. As your skill and programming knowledge improves. you will find more uses for your disk drive and the more advanced chapters of this manual willbecome much more valuable.

If you're a professional, this reference guide will showyou how to put the 1541 through its paces to perform just about all the disk drive jobs you can

think of.

No matter what level of expertise you have, your 1541 disk drive will

dramatically improve the overall capabilities of your computer system.

Before you get to the details of 1541 operation, you should be aware of a few important points. This manual is a REFERENCE GUIDE, which means that unless the information you seek directly pertains to the disk or disk drive you will have to useyour Commander 64 or VIC 20 User's Guides and Programmer's Reference Guides to find programming information. In addition, even though we

give you step-by-step instructions for each operation, you should become

familiar with BASIC and the instructions (called commands) that help you operate your disks and drives. However. if you just want to use your disk drive

unit to load and save prepackaged software, we've included an easy and brief

section on doingjust that.

Now. . . let's get on with the general information.

The commands for the disk drive come in several levels of sophisication. Starting in chapter three. you can learn how the commands that allow you to save and load programs with the disk work. Chapter four teaches you how

commands are sent to the disk, and introduces the disk maintenance commands.

Chapter five tells you how to work with sequential data files. These arl very similar to their counterparts on tape (but much faster). Chapter sif

introduces the commands that allow you to work with random files, accessany piece of data on the' disk, and how you organize the diskette into tracks and

blocks. Chapter seven describes the special relative files. Relative files are the best method of storing data bases, especially when they are used along with sequential files.

Chapter eight describes methods for programming the disk controller

circuits at the machine language level. And the final chapter shows you how to

change the disk device number. by "cutting" a line inside the drive unit or through software.

Remember, you don't really need to learn everything in this book all at

once. The first four chapters are enough to get you going, and the next couple are enough for most operations. Getting to know your disk drivewill reward you in many ways-speed of operation, reliability, and much more flexibility in your

data processing capabilities. Specifications

This disk drive allows you to store up to 144 different programs and/or

data files on a singlemini-floppy diskette, for a maximum of over 174,000 bytes worth of information storage.

Included in the drive is circuitry for both the disk controller and a

complete disk operating system, a total of 16K of ROM and 2K of RAM memory. This circuitry makes your Commodore 1541 disk drive an "intelligent"

device. This means it does its own processing without taking any memory away from your Commodore 64 or VIC 20 computer. The disk uses a "pipeline"

software system. The "pipeline" makes the disk abot to process commands while

the computer is performing other jobs. This dramatically improves the overall throughput (input and output) of the system.

Diskettes that you create in this disk drive are read and write compatible

with Commodore 4040 and 2031 disk drives. Therefore, diskettes can be used interchangeably on any of these systems. In addition, this drive can read

programs created on the older Commodore 2040 drives.

The 1541 disk drive contains a dual "serial bus" interface. This bus was

specially created by Commodore. The signals of this bus resemble the parallel IEEE-488 interface used on Commodore PET computers, except that only one wire is used to communicate data instead of eight. The two ports at the rear of

the drive allows more than one device to share the serial bus at the same time. This is accomplished by "daisy-chaining" the devices together, each plugged into

the next. Up to fivedisk drivesand one printer can share the bus simultaneously.

Figure 1.1 Specifications VIC 1540/1541 Single Drive Floppy Disk

STORAGE

Total capacity

Sequential Relative

Directory entries Sectors per track

Bytes per sector Tracks

Blocks

lC's:

6502 6522 (2)

Buffer

2114 (4)

PHYSCIAL:

Dimensions

Height Width

Depth

Electrical:

Power requirements

Voltage

Frequency

Power

174848 bytes per diskette 168656 bytes per diskette 167132 bytes per diskette 65535 records per file 144 per diskette

17 to 21 256

35 683 (664 blocks free)

microprocessor I/O. internal timers

2K RAM

97mm 200 mm 374 mm

O, 120,220, or 240 VAC

5 or 60 Herts

2 Watts

MEDIA:

Diskettes

Standard mini 5\4", singlesided,

singledensity

2. UNPACKING AND CONNECTING

Contents of Box

power cable, black serial bus cable, this manual, and a demonstration diskette.

The power cable has a connection for the back of the disk drive on one end, and

for a grounded (three-prong) electrical outlet on the other. The serial bus cable is

exactly the same on both ends. It has a 6-pin DIN plug which attaches to the

VIC 20, Commodore 64 or another disk drive.

section!

Fig 1. Front Panel LIGHT:POWERON

Fig2. BackPanel

Included with the 1541 disk drive unit, you should find a gray

Please, don't hook up anything until you've completed the following

(: commodare_ floppy disk ~ VIC. 541

_single drive

DRIVE INDICATER (RED LED)

POWER INDICATER (GREEN LED)

POWER SWITCH

LIGHT: ACTIVE FLASH: ERROR

SERIAL BUS

Connection of Cables

Your first step is to take the power cable and insert it into the back of the

disk drive (see figure 2.2). It won't go in if you try to put in in upside down.

Once it's in the drive, plug the other end into the electrical outlet. if the disk drive makes any sound at this time, please turn it off using the switch on the back! Don't plug any other cables into the disk drive if the power is on.

Next. take the serial bus cable and attach it to either one of the serial bus sockets in the rear of the drive. Turn off the computer, and plug the other end of the cable into the back of the computer. That's all there is to it!

If you have a printer, or any additional disk drives, attach the cables into the second serial bus port (see figure 2.3). For directions on using multiple drives at one time, read chapter 8. If you are a first-time user with more than one drive, start working with only one drive until you're comfortable with the unit.

---_.--_.-.---._-_..

r u --- ..---.--.

Powering On

When you have all the devices hooked together, it's time to start turning on the power. It is important that you turn on the devices in the correct order. The computer should always be turned on last. As long as the computer is the last one to be turned on, everything will be OK.

Commodore 64 or VIC20

Personal Computer

VIC Graphic Printer

Fig 3. Floppy Disk Hookup

VIC 1541 Single Drive Floppy Disk

I i

First, make sure that you've removed all diskettes from the disk drives before powering on.

After all the other deviceshave been turned on, only then is it safe to turn

on the computer. All the other devices will go through their starting sequences.

The printer's motor goes on, with the print head movinghalfway across the line

and back again. The 1541 disk drive will have its red error light on, and then the green drivelight will blink, whileyour TV screen forms the starting picture.

Once all the lights have stopped flashing on the drive, it is safe to begin

working with it.

m :c

'-I

WRITE

PROTECT

NOTCH

WHEN COVERED. DISKETTE CONTENTS CANNOT BE AL TERED

~ <:

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-I

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Fig.4. Position for Diskette Insertion

Insertion of Diskette

To open the door on the drive, simply press the door catch lightly, and the door will pop open. If there is a diskette in the drive, it is ejected by a small spring. Take the diskette to be inserted, and place it in the drive face-up with the

large opening going in first and the write-protect notch to the left (covered with

tape in the demonstration disk) (see figure 2.4).

Press it in gently, and when the diskette is in all the way, you will feel a click and the diskette will not spring out. Close the drive door by pulling downward until the latch clicks into place. Now you are ready to begin working

with the diskette.

Remember to always remove the diskette before the drive is turned off or on. Never remove the diskette when the green drive light is on! Data can be

destroyed by the drive at this time! UsingWith a VIC 20 or Commodore 64

The 1541 Disk Drive can work with either the VIC 20 or Commodore 64

computers. However, each computer has different requirements for speed of incoming data. Therefore, there is a software seitch for selecting which computer's speed to use. The drive starts out ready for a Commodore 64. To switch to VIC 20 speed, the foIlowing command must be sent after the drive is started (power-on or through software):

OPEN 15,8,15, "UI-": CLOSE 15

To return the disk drive to Commodore 64 speed, use this command:

OPEN 15,8, 15, "UI+": CLOSE 15

More about using this type of command is in chapter 4, with a detailed

explanation of the U (user) commands in chapter 7.

3. USING PROGRAMS

LOADINGPREPACKAGED PROGRAMS

For those of you interested in using only prepackaged programs available

on cartridges, cassette, or disk, here's all you have to do:

Usingyour disk drive, carefully insert the preprogrammed disk so that the label on the disk is facingup and isclosest to you. Look for a little notch on the disk (it might be covered with a little piece of tape). If you're inserting the disk properly, the notch will be on the left side. Once the disk is inside, close the protective gate by pushing in on the lever. Now type LOAD "PROGRAM NAME", 8 and hit the .~U"IU~~. key. The disk will make noise and your screen willsay:

When the READY comes on and the:~:is on, just type RUN, and your

prepackaged software is ready to use.

LOAD

The BASICcommands used with programs on the disk drive are the same

as the commands used on the Commodore DatassetteTM recorder. There are a

few extra commands available for use with disks, however. First of all, the program name must be given with each command. On a Datassette, you could omit the program name in order to just LOAD the firs program there. On disk, since there are many different programs that are equally accessible, theprogram

name must be used to tell the disk drive what to do. In addition, the disk drive's

device number must be specified. If no device number is listed, the computer

assumes the program is on tape.

FORMAT FOR THE LOAD COMMAND:

LOAD name$ , device# , command#

The program name is a string, that is, either a name in quotes or the contents of a given string variable. Some valid names are: "HELLO", "PROGRAM #1", A$, NAME$.

The device# is preset on the circuit board to be #8. If you have more than one drive, seechapter 8 on how to change the devicenumber. This book assumes that you're using devicenumber 8 for the disk drive.

The command# is optional. If not given, or zero, the program is LOADed normally, that is, beginning at the start of your available memory for BASIC programs. If the number is I, the program will be LOADed at exactly the same memory locations from which it came. In the case of computers with different memory configurations, like VICs with 5K, 8K, or more memory, the start of BASIC memory is in different places. The command# 0 permits BASIC programs to LOAD normally. Command# I is used mainly for machine language, character sets, and other memory dependent functions.

EXAMPLES

LOAD "TEST", 8

LOAD"Mach Lang", 8, I

NOTE: You can use variables to represent devicenumbers, commands, and strings, as long as you've previously defined them in your program.

Directory of Diskette

Your Datassette™ tape deck is a sequential device. It can only read from the beginning of the tape to the end, without skipping around the tape and without the capability of goingbackward or recording over old data.

Your disk drive is a random access device. The read/write head of the disk

can go to any spot on the disk and access a single block of data which holds up

to 256 bytes of information. There are a total of 683 blocks on a single diskette.

.Fortunately, you don't really have to worry about individual blocks of data. There is a program in the disk drive called the Disk Operating System, or the DOS. This program keeps track of the blocks for you. It organizes them into

a Block Availability Map,or BAM,and a directory. 10

The Block Availability Map is simply a checklist of all 683 blocks on the disk. It is stored in the middle of the diskette, halfway between the center hub and the outer rim. Every time a program is SAVEd or a data file isCLOSEd, the BAMis updated with the list of blocks used up.

The directory is a list of all programs and other files stored on the disk. It is physically located right next to the BAM.There are 144 entries available in the directory, consisting of information like file name and type, a list of blocks used, and the starting block. The directory is automatically updated every time a program is SAVEd or a file is OPENed for writing. Beware: the BAM isn't updated until the file is CLOSEd, even though the directory changes right away. If a file isn't CLOSEdproperly, all data in that me will probably be lost.

The directory can be LOADed into your memory just like a BASIC program. Place the diskette in the drive, and type the following command:

LOAD"$",8

The computer responds with:

Now the directory is in your computer's memory. Type LIST, and you'll see the directory displayed on the screen. To print the directory on your printer,

type the following command line (in this example your printer is plugged in as

device# 4):

OPEN4, 8,4: CMD4: LIST

NOTE: When using CMD, the file must be closed using the command

PRINT# 4: CLOSE 4. See the VIC 1525/1515 printer manual for detailed

explanation.

To read the directory without LOADing it into your memory, see the

section later in this chapter on the DOS Support Program. In addition, to examine the directory from inside a BASICprogram. see the section in chapter 5

that deals with the GET# statement.

Pattern Matching and Wild Cards

When using the tape deck, you can LOAD any program starting with

certain letters just by leaving off any following letters. Thus, the command

LOAD "T" will find the first program on the tape beginning with the letter T. And LOAD "HELLO" will find the first program beginning with the letters HELLO, like "HELLO THERE."

When using the disk, this option is called pattern matching, and there is a special character in the file name used to designate this. The asterisk (*) character following any program name tells the drive you want to find any program starting with that name.

FORMAT FOR PATTERN MATCHING:

Can BeA String Variable Or The

LOADname$ + "*", 8

Name Inside Quotes

In other words, if you want to LOAD the first program on the disk starting with the letter T, use the command LOAD "T*", 8.

If only the "* is used for the name, the last program accessedon the disk is the one LOADed. If no program has yet been LOADed, the first one listed in the directory is the one used.

You are probably familiar with the concept of wild cards in poker where one card can replace any other card needed. ,On your 1541, the question mark (?) can be. used as a wild .card on the disk. The program name on the disk is compared to the name in the LOAD command, but any characters where there is

aquestionmarkinthe namearen't checked. '

For instance, when the command LOAD "T?NT", 8 is given, programs

that match include TINT, TENT, etc.

When LOADingthe directory of the disk, pattern matching and wild cards can be used to check for a list of specific programs. If you gave the command LOAD "$O:TEST", only the program TEST would appear in the directory (if present on the disk). The command LOAD "$O:t*" would giveyou a directory of aUprograms beginning with the letter T. And LOAD "$O:T?ST" would give

you all the programs with 4-letter names having the first letter of T and the third

and fourth letters ST. LOAD "$O:T?ST*" would give names of any length with the correct first, third, and fourth letters.

SAVE

To SAVE a program to the diskette, all that is needed is to add the device number after the program name. Just like the SAVE command for the tape deck, the device number can be folJowedby a command number, to prevent the

automatic re-Iocation on LOADing (see the section on the LOAD 'command, above).

FORMAT FOR THE SAVE COMMAND:

SAVE name$, device#, command#

See the LOAD ~ommal1d (pages

parameters device# and command#.

When you tell the disk drive to SAVE a program, the DOS must take several steps. First, it looks at the directory to see if a program with that name already exists. Next it ~he~ks to see that there is a directory entry availablefor the name. Then it che~ks the BAMto see if there are enough blocks in which to store the program. If everything is OKup to this point, the program is stored. If not, the error light willflash.

SAVE and Replace

If a program already exists on the disk, it is often necessary to make a ~hange and re-SAVE it onto the disk. In this case, it would be inconvenient to have to erase the old version of the program and then SAVE it.

If the first characters of the program name are the "(aP'signfollowed by a o and a colon (:), the DOS knows to replace any old program that has that name with the program that is now in the computer's memory. The drive checks the directory to find the old program, then it marks that entry as deleted, and it next creates a new entry with' the same name. Finally, the program is stored normally.

FORMAT FOR SAVE WITHREPLACE:

SAVE "=0:" + nameS, device#, command#

For example, if a file was called TEST, the SAVE and replace command would be SAVE"(u,O:TESr,8.

) for an explanation of the

____

The reason for the 0: is to keep compatibility with other Commodore disk drive units which have more than one drive built in. In that case, the number 0

or 1is used to specify which drive isbeing used. VERIFY

The VERIFY command works to check the program currently in memory

against the program on disk. You must include a device# with the VERIFY

command. The computer does a byte-by-byte comparison of the program,

including line links-which may be different for different memory configura- tions. For instance, if a program was SAVEd to disk from a 5K VIC 20, and re-LOADed on an 8K machine, it wouldn"t VERIFY properly because the links point to different memory locations.

FORMAT FOR VERIFY COMMAND:

VERIFY name$, device#

DOS Support Program

On your demonstration

disk, there may be a program called DOS

SUPPORT.This program, also called a wedge,allowsyou to use many disk

commands more easily (different wedges are used for the VIC 20 and the Commodore 64). Just LOAD the program and RUN it. It automatically sets

itself up and erases itself when it's finished. You'll have a few hundred less bytes to work with when this program is running, but you'll also have a handy way to

send the disk commands.

As a result of the DOS Support, the "/" key now takes the place of the LOAD command. Just hit the slash followed by the program name, and the program is LOADed. When you use this method, you don't need to use the

LOADcommand or the comma 8.

Thc"(Q)"and ">" keys are used to send commands to the disk drive. If you type (a$ (or >$), the directory of the disk is displayed on the screen, without

LOADinginto your memory! Thesekeysalsotaketheplaceof thePRINT#(see

chapter 4) to send commands listed in the next chapter.

To read the error channel of the disk (when the red error light is blinking),

just hit either the (a'or the> and hit RETURN. The complete error message is

displayed to you: messagenumber, text, and track and block numbers.

4: DISK COMMANDS

OPEN and PRlNT#

Up 'til now, you have explored the simple ways of dealing with the disk

drive. In order to communicate with the disk drive more fully, you have to touch on the OPEN and PRINT# statements in BASIC(more details of these commands are available in your VIC 20 or Commodore 64 User's Guide or

Programmer's Reference Guide). You may be familiar with their use with data files on cassette tape, where the OPEN statement creates the file and the PRINT# statement fills the file with data. They can be used the same way with

the disk, as you will see in the next chapter. But they can also be used to set up a command channel. The command channel lets you exchange information between the computer and the disk drive.

FORMAT FOR THE OPEN STATEMENT:

OPENfile#, device#, (command) channel#, text $

The file# can be any number from I to 255. This number is used

throughout the program to identify which file is being accessed. But numbers

greater than 127 should be avoided, because they cause the PRINT# statement to generate a linefeed after the return character. These numbers are really meant

to be used withnon-standard printers. 14

The device# of the disk is usually 8. The channel # can be any number from 2 to 15. These refer to a channel

used to communicate with the disk, and channels numbered a and I are reserved for the operating system to use for LOADingand SAVEing.Channels::: through

14can be used for data to files, and 15is the command channel.

The text$ is a string that is PRINTed to the file, as if with a PRINT#

statement. This ishandy for sending a single command to the channel.

EXAMPLES OF OPEN STATEMENTS:

OPEN 15,8, IS DEViCE-#~\

OPEN2,8. 2 C-- ~~

OPENA;B,C,ZL ~

The PRINT# command works exactly like a PRINT statement, except

that the data goes to a deviceother than the screen, in this case to the disk drive.

When used with a data channel, the PRINT# sends information into a buffer in

the disk drive, which LOADs it onto the diskette. When PRINT# is used with the command channel, it sends commands to the disk drive.

FORMAT FOR SENDING DISK COMMANDS:

OPEN 15, 8, IS. command$

PRINT# IS, command$

NEW

This command is necessary when using a diskette for the first time. The NEW command erases the entire diskette, it puts timing and block markers on the diskette and creates the directory and BAM.The NEWcommand can also be used to clear out the directory of an already.formatted diskette. This is faster than re-formatting the whole disk.

FORMAT FOR THE NEWCOMMANDTO FORMATDISK:

PRINT#15, "NEW~~'

or abbreviated as

PRINT#15, "N~:name,id"

FORMAT FOR THE NEW COMMAND TO CLEAR DIRECTORY:

PRINT# 15, "N~:name"

The name goes in the directory as the name of the entire disk. This only

appears when the directory is listed. The ID code is any 2 characters, and they are placed not only on the directory but on every block throughout the diskette.

That way, if you carelessly replace diskettes while writing data, the drive will know by checking the ID that something is wrong.

COpy

This command allows you to make a copy of any program or file on the disk drive. It won't copy from one drive to a different one (except in the case of dual driveslike the 4040), but it can duplicate a program under another name on

the drive.

FORMAT FOR THE COPYCOMMAND:

PRINT# 15, "COPY~:newfile=~:oldfile" or abbreviated as

PRINT# 15, "c~:newfile=~:oldfile"

The COpy command can also be used to combine two through four flles

on the disk.

FORMAT FOR COpy TO COMBINE FILES:

PRINT#15, "CO: newfile=O: old file I,0:0Idfile2,0:0Idfile3 ,0:0Idfile4"

EXAMPLES OF COPY COMMAND:

PRINT# 15, "CO:BACKUP=O:ORIGINAL"

PRINT#15, "CO:MASTERFILE=O:NAME,O:ADDRESS,O:PHONES"

RENAME

~ "'"

This command allows you to change the name of a file once it is in the disk directory. This is a fast operation, since only the name in the directory must

be changed.

FORMAT FOR RENAME COMMAND:

~-~

PRINT# IS, "RENAME~:newname=oldname" ~

or abbreviated as

PRINT# IS, "R~:newname=oldname" EXAMPLE

OPEN.

OF RENAME COMMAND:

PRINT# 15, "RO:MYRA=MYRON"

The RENAME command willnot work on any files that are currently

SCRATCH

This command allows you to erase unwanted files and programs from the

disk, which then makes the blocks available for new information. You can erase programs one at a time or in groups by using pattern matching and/or wild cards.

FORMAT FOR SCRATCHCOMMAND

PRINT# 15,"SCRATCH~:~

or abbreviated as

PRINT# 15, "S~:name"

If you check the error channel after a scratch operation (see below), the number usually reserved for the track number now tells you how many files were scratched. For example, if your directory contains the programs KNOW and GNAW, and you use the command PRINT# 15, "SO:?N?W", you will scratch both programs. If the directory contains TEST, TRAIN, TRUCK, and TAIL, and you command the disk to PRINT# 15, "SO:T*", you will erase all four of these programs.

INITIALIZE

At times, an error condition on the disk willprevent you from performing some operation yo~ want to do. The INITIALIZE command returns the disk drive to the same state as when powered up. You must be careful to re-match the drive to the computer (see chapter 2).

FORMAT FOR INITIALIZE COMMAND:

PRINT# 15,"INITIALIZE" or abbreviated as

PRINT# 15, ''!''

VALIDATE

After a diskette has been in use for some time, the directory can become disorganized. When programs have been repeatedly SAVEd and SCRATCHed, they may leave numerous small gaps on the disk, a block here and a few blocks there. These blocks never get used because they are too small to be useful. The VALIDATE command will go in and re-organize your diskette so that you can get the most from the availablespace.

Also, there may be data files that were OPENed but never properly CLOSEd. This command will collect all blocks taken by such files and make them available to the drive, sincethe files are unusable at that point.

There is a danger in using this command. When using random files (see chapter 6), blocks allocated will be de-allocated by this command. Therefore, this command should never be used with a diskette that usesrandom files.

+ 45 hidden pages

Commodore VIC 1541 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual