Commodore 1551 User manual

COMMODORE
1551
DISK DRIVE
USERJS GUIDE
A Friendly Introduction to Your 1551 Diek Drive

The information in this manual has been reviewed and is believed to be entirely reliable.
No responsibility, however,
is assumed for inaccuracies. The material in this manual is
for information purposes only, and may be changed without notice.
© Commodore Electronics Ltd., October 1984
"All rights reserved."

CONTENTS
INTRODUCTION ...................................................... 1
Advantages ofa disk
drive. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1
Features ofthe 1551 ..•.•....................................... 1
How to use this book. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
PART ONE: GUIDE TO OPERATION
.................................... 3
CHAPTER 1: DISK DRIVE
.........•................................... 3
Unpacking
........•..................................•........ 3
Connecting the cables . . . •. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 4
Turning on the
power. . . •. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5
Troubleshooting guide .......................................... 6
Simple maintenance tips. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7
CHAPTER 2: DISKETTES
..............•............................... 9
What
is a diskette? .•...•.......•..........................•.... 9
Safety rules for diskette care
.....•.............................. 10
Using packaged programs .......•.............................. 10
How to prepare a new diskette ...•..........•...............•... 12
Organizing a diskette library. . . . . . . . . . . . . . . . . . . . . . . . . . . . •. . . . . .. 12
Backups ......................•................... ' ........... 13
What is a directory? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13
Viewing a directory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14
What a directory shows ........................................ 14
CHAPTER 3: OPERATION . . . . . •. . . . . . . •. . . . . . . . . . . •. . . . . . . . •. . . . . . . .. 16
The command channel . . . . . . . . . . . . . . •. . . . . . . . . . . . . . . . . . . . . . . . .. 16
Error checking. . . . . . . . . . . . . . . . . . . . . •. . . . . . . . . . . . . . . . . . . . . . . . .. 17
Error check subroutine ......................................... 17
BASIC housekeeping hints. . . . . . . . . . . •. . . . . . . . . . . . . . . . . . . . . . . . .. 17
More about directories. . . . . . . . . . . . . . •. . . . . . . . . . . . . . . . . . . . . . . . .. 18
Selective directories ............................................ 19
Printing a directory. . . . . . . . . . . . . •. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 19
Pattern matching and wild cards ................................. 19
Splat files ..•......................•.......................... 20
Verify .•......................•.............................. 22
Copy ..•....•................................................ 23
Scratch •..............•..•....•.......•..............••...... 24
Rename •......................•.............................. 26
Renaming and scratching troublesome files (advanced users) ......... 26
Collect. ....•..•......................•.....................•. 27
Initialize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . •. . . . . . . . . . . . . . . . . . . . .. 28

PART TWO: GUIDE TO ADVANCED OPERATION AND PROGRAMMING 31
CHAPTER 4: SEQUENTIAL DATA FILES ............................... 31
The concept of files ............................................ 31
Opening a file. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 32
Adding to a sequential file .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 34
Writing file data: Print # ....................................... 35
Closing a
file when you are done using it . . . . . . . . . . . . . . . . . . . . . . . . .. 37
Reading file data: Input # ...................................... 38
More about Input # (advanced users) ............................ 39
Numeric data storage on diskettes ................................ 40
Reading file data: Get # ........................................ 41
CHAPTER 5: RELATIVE FILES ................•...................... 44
The value ofrelative access ..................................... 44
Files, records, and fields ........................................ 44
File limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 45
Creating a relative file
.......................................... 45
Using relative files: Record # command
........................... 46
Completing relative file creation
................................. 48
Expanding a relative file. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 49
Writing relative file data ........................................ 50
Designing a relative record. . . . . . . . . . . . . . . . •. . . . . . . . . . . . . . . . . . .
.. 50
Writing the record
....................•........................ 51
Reading a relative record. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 53
The value of index files (advanced users) .......................... 54
CHAPTER 6: DIRECT ACCESS COMMANDS
........................... 55
A tool for advanced
users. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 55
Diskette organization .......................................... 55
Opening a data channel for direct access . . . . •. . . . . . . . . . . . . . . . . . . .. 55
Block-read ................................................... 56
Block-write. . . . . . . . •. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 57
The original Block-read and Block-write commands . . . . . . . . . . . . . . .. 58
The buffer pointer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 59
Allocating blocks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 60
Freeing blocks
....••.......................................... 61
Using random files (advanced users) .............................. 62
CHAPTER 7: INTERNAL DISK COMMANDS .......•.........•.......... 63
1551 memory map .............•............................... 63
Memory-read
................................................. 64
Memory-write
.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 65
Memory-execute .........................................•.... 66
Block-execute
...•.........•................•.................. 67
User commands
.••....................•....................... 68

CHAPTER 8: MACHINE LANGUAGE PROGRAMS ...................... 70
Disk-related kernal subroutines .................................. 70
APPENDICES ........................................................ 71
A: Changing the device number ................................. 71
B: DOS error messages and likely causes ...........•............. 73
C: Diskette formats ........................................... 77
D: Disk command quick reference ............................... 82
E: Test/Demo diskette
......................................... 83
F: Specifications of the 1551 disk drive ........................... 86
LIST OF FIGURES
Figure 1:
Front panel
Figure 2: Back panel
Figure 3: Single and twin drive hookup
Figure 4: Position for diskette insertion

INTRODUCTION
The 1551 disk drive greatly increases the speed, storage capacity, flexibility and reliabil-
ity of your Commodore computer. As you use the 1551 disk drive, you will appreciate its
superiority to the cassette recorder you may have used before and to disk drives offered for
other brands
of computers.
THE ADVANTAGES OF A DISK DRIVE
• Speed
If you have used a cassette recorder for data storage, you probably know it can take up
to an hour just to search one long cassette tape looking for a specific program. With the
1551 disk drive, a list of all the programs on a diskette appears on your screen in
seconds. The speed of program loading is also greatly improved. It takes the 1551 only
a minute to load a large program that would take a half-hour to load from tape.
• Reliability
Reliability
is another reason for choosing a disk drive. It is all too common for a cassette
user to accidentally crase a valuable program
by saving a new program on top of the old
one, without realizing it. The
1551 automatically verifies everything it records.
• Direct File Access
A third advantage
of a disk drive is the ability to use relative files (discussed in Chapter
6). On a diskette, any part
of a relative file can be accessed and altered separately,
without affecting the rest
of the file.
Overall, using a disk drive makes for easier and more powerful computing.
FEATURES OF
THE 1551
The
1551 is one of the most affordable disk drives on the market. Compared to
competitors, it has high capacity, and even higher intelligence. It
is one of the most co,t-
effective disk drives available. Most home and personal computers that use a disk take
at
least 10K of RAM memory from the computer to hold a disk operating system (known as
a DOS.) This large program must
be in memory the whole time the disk is being used, and
much
of it must also be kept on every diskette.
The Commodore
1551 works differently and more effectively. It contains its own
built-in microcomputer
to control its various operations, along with enough ROM and
RAM memory to operate without any help from the computer. Commodore's DOS
"lives" entirely inside the disk drive, and does not require any internal memory in the
computer
to do its work, nor does it have to be loaded before use like DOS on other
computers. It
is so independent that once it begins working on a command, it will
complete it while the computer goes on to some other task, effectively allowing you to do
two things at once.
Another key advantage
of the Commodore 1551 overdisk drives for other computers
is its dynamic allocation of disk space. Many other disk drives make you think about
every program you save. Where can I store
it on this diskette, and should I paek the disk

first? (Packing is the process of moving all the leftover work areas to the cnd of the
diskette's storage space.) All this
is handled automatically on Commodore disk drives.
The
1551 always knows where the next program will go, and automatically fits it into the
best available spot.
Diskettes created on the 1551 are read and writc compatible with Commodore 1540/
1541,4040, and 2031 disk drives. That means that diskcttes can be used interchangeably
on any
of these systcms. In addition, the 1551 can read programs created on the older
Commodore 2040 drives.
The
1551 is connected to the computer through the "TCBM" interface. This
interface
is specially created by Commodore. Bytes are transferred as parallel data with a
3-bit bi-directional port, two handshake lines, and two status lines. This handshake
protocol allows for less timing constraint than the slower serial interfaces. Estimated data
rate over the TCBM handshake is 1600 bytes per second versus 300-400 bytes per second
for the
1541 drive. The 1551 connector plugs into the host computer's expansion port and
allows external cartridges to be plugged in. You can have two
1551 drives, two 1541
drives, and two printers hooked up to the computer at once as long as each peripheral is
assigned a different device number. When there is contention with duplicate device
numbers, the
1551 has priority over the 1541.
HOW TO USE THIS BOOK
This book is divided into two main parts. The first part gives you the information you
need to use the
1551 effectively, even if you know little or nothing about programming.
This part
of the book tells you how to set up the system, how to prepare diskettes for use,
how to read a directory, how
to load programs, and various commands. Part two of the
book
is for advanced users and those who would like to become advanced users. This part
provides more advanced commands, tells about the different files the
1551 uses, and how
to manage them, as well as giving a few hints for machine language programmers.
Both beginning and advanced users will
find valuable information in the appendi-
ces-a quick reference list of disk commands, a list of disk error messages and what they
mean, specifications for the
ISS\, how to use two or more disk drives at once, and
explanations
of some programs on the Test/Demo diskette packed with your 1551.
If you are interested only in using pre-packaged programs such as educational or
recreational software, you can turn
to the section entitled "Using packaged programs" in
Chapter 2. First of all, you'll have to hook up your disk drive according to the directions
in Chapter I.
2

PART 1: GUIDE TO OPERATION
UNPACKING
CHAPTER 1
DISK DRIVE
The first thing you will need to do with your disk drive is unpack it. Inside the carton
in which you found this manual, there should also be: a 1551 disk drive, a gray power
r
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\ DOOR LEVER
DRIVE INDICATER (RED LED) LIGHT
FLASH
POWER INDICATER
(GREEN LED) LIGHT: POWER ON
Figure 1. Front Panel
3
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cord, and an interface cable with a connection for a memory expansion bus. The
connector can also
be hooked up to another 1551 and a cartridge. Also included is a Test/
Demo diskette and a warranty card to
be filled out and returned to Commodore.
Please don't connect anything until you've read the next three pages.
It could save
you a lot
of trouble.
After unpacking the unit, make sure nothing
is inside the disk drive. If you turn the
power off or on with a diskette in the drive, you could lose its contents.
To check whether the drive
is empty, simply rotate the lever on the front of the disk
drive counter-clockwise until it stops (see Figure 1), one-quarter tum at most. Then reach
inside the long slot the lever covers when
it points down, and pull out the cardboard
shipping spacer inside. Don't throw it away. You will want to put
it back inside the slot
any time you move or ship the disk drive later.
CONNECTING THE CABLES
The power cable plugs into the back ofthe disk drive
at one end, and into a grounded
(3-prong) outlet at the other end.
It will only go in one way. Before you plug it in though,
make sure that your entire computer system
is turned off. The disk drive's on/offswitch is
in the back, on the left side (see Figure 2). It is off when the portion marked "off' is
pushed inward. Leave your whole system off until everything is connected.
After plugging the power cord into the disk drive and a suitable outlet, take the
interface connector and insert
it into the Memory Expansion slot of your computer. That's
all there
is to it (see Figure 3).
If you have another
1551 disk drive, plug that interface connector into the slot in the
first interface connector. Don't try to use more than one disk drive until you've learned
how to change their device numbers,
as no two disk drives can have the same device
number. We'll cover ways
of changing disk device numbers in Appendix A. Until you are
ready
to read that section, you may find it easier to leave your extra drive(s) unconnected
(see Figure 4).
POWER SWITCH
FUSE/HOLDER
Figure 2. Back Panel
4

Single Drive
Multiple Drive
Figure 3. Disk Drive to Computer Hookup
TURNING ON THE POWER
With everything hooked up, and the disk drive empty, it is time to turn on the power.
You can turn on the power to the drive and any other devices that may be connected
in any
order you like. Just
be sure to either turn on the power to the computer itself last, or to use
a multiple outlet power box with a master switch to turn everything off and on at once.
When everything
is on, including the computer, the disk drive will go through a selfcheck
for a second
or so, to be sure it is working correctly. After the drive is satisfied with its
own health, it will flash the red light below the drive door once, and the green power-on
light to the left
of the drive door will glow continuously. At the same time, the computcr
will be going through a similar self-test, and displaying
its hello message on your TV or
video monitor. Once the red light on the disk drive has flashed and gone out, it
is safe to
begin working with the drive.
If the light doesn't go out, but continues to flash, you may
have a problem. Refer to the troubleshooting guide for help.
5

TROUBLESHOOTING GUIDE
Symptom
Green indicator light
on the
1551 not on
Cause
Disk drive not
turned on
Power cable not
plugged
in
Power off to
wall outlet
Bad fuse
in
disk drive
Remedy
Make sure power switch
is in the "on" position
Check both ends
of power
cable to be sure they
are fully inserted
Replace fuse or reset
circuit breaker
in house
Replace fuse (located
on back panel, as shown
in Figure 2) with one of
same size and rating
(Ifany fuse fails twice, added help
is needed. If the house fuse failed, you may need an electrician. If
the drive fuse failed, call your dealer.)
Red error light The disk drive
is
on drive flashes failing its power-on
continously on self-test
power-up, before
any disk commands
have been given
Tum the system off for
a minute and try again.
If it repeats, try again
with the interface cable
disconnected. If
it
still repeats, call your
dealer. If unplugging
the interface cable made a
difference. check the
cable for proper
connection.
(The principle behind unplugging the interface cable
is "divide and conquer." The drive can do its
power-on test even when not connected
to a computer. If it succeeds that way, then the problem is
probably in the cable or the rest of the system. not the 1551.)
Programs won't load, and
computer says
"DEVICE
NOT PRESENT ERROR."
Programs won't load, but
computer and disk drive
give no error message.
Interface connector
not well connected, or
disk not turned on.
Another device in the
memory expansion slot
may be interfering.
Be sure interface connector
is correctly inserted
and disk drive
is turned
on
Unplug all other devices
on the computer. If
that cures it. plug them
in one at a time. The
one just added when the
trouble repeats is most
likely the problem.
Also, trying to load a
machine language program
into BASIC space will
cause this problem.
(Such devices may not be turned on properly, or may have conflicting device numbers. Only one
device on the cable can have
anyone device number.)
6

TROUBLESHOOTING GUIDE
Symptom
Programs won't load,
and disk error light
flashes.
Cause
A disk error has
occurred.
Remedy
Check the disk error
channel
to see why the
error occurred. Follow
the advice
in Appendix B
to correct it.
(Be sure to spell program names exactly right, as the disk drive is very particular. even about spaces
and punctuation marks, and will not load a program unless you call
it exactly the same thing it was
called when
it was saved on the diskette.)
Your own programs Load
fine, but commercial
programs and those
from other
1551 owners
fail
to load.
Your own programs that
used
to Load won't
any more, but programs
saved on newly-formatted
diskettes still work.
Either the diskette you
are loading is faulty,
(some mass-produced
diskettes are) or your
disk drive is misaligned.
Older diskettes have
been damaged.
The disk drive has gone
out of alignment.
SIMPLE MAINTENANCE TIPS
Try another copy of the
troublesome programs. If
several programs from
several sources
al ways
fail
to load, have your
dealer align your
disk drive.
See the section on safety
rules for diskette care.
Recopy from backups.
Have your dealer align
your disk drive.
Your 1551 should serve you well for years to come, but there are a few things you
can do to avoid costly maintenance.
1. Keep the drive well-ventilated. Like a refrigerator, it needs a few inches of air
circulation on all sides to work properly. If heat can't be avoided any other way, you
may
cool the drive by placing a small filtered fan on the drive so its air blows into the cooling
slots. (An inexpensive air freshener is quite suitable for this.) However, the added air flow
will result in more dirt getting in the drive.
2. Use only good quality diskettes. Badly-made diskettes could cause increased wear on
the drive's read/write head. Ifa particular diskette
is unusually noisy in use, it is probably
causing added wear, and should
be replaced.
3. Avoid using programs that
"thump" the drive as they load. Many commercial
programs, and diskettes that are failing, cause the disk drive to make a bumping or
chattering noise as it attempts to read a bad sector. Ifthe diskette can be copied to a fresh
diskette, do so immediately. If it
is protected by its maker against copying, the thumping
is intentional and will have to be endured.
4. It would be a good idea to have your
1551 checked over about once a year in normal
use. Several items are likely to need attention: the felt load pad on the read/write head may
7

be dirty enough to need replacement, the head itself may need a bit of cleaning (with 91 %
isopropyl alcohol on a cotton swab), the rails along which the head moves may need
lubrication (with a special Molybdenum lubricant, NOT oil), and the write protect sensor
may need to
be dusted to be sure its optical sensor has a clear view. Since most of these
chores require special materials or parts,
it is best to leave the work to an authorized
Commodore service center. If you wish to do the work yourself, ask your dealer to order
the
1551 maintenance guide for you (part number 990445), but be aware that home repair
of the
1551 will void your warranty.
8

WHAT IS A DISKETTE?
CHAPTER 2
DISKETTES
Before we actually begin using the drive, let's take a moment to look at the
Test/Demo diskette packed with the disk drive. To do this, grasp it
by the label, which
should
be sticking out of the paperjacket. Then pull it out of the jacket which keeps it free
of dust and other contaminants. (Save the jacket; the diskette should always be kept in its
jacket except when actually
in use in the disk drive.) It is often called a floppy diskette,
because
it is flexible, but do not bend it.
A diskette is much like a cassette tape, but in the form
of a circle and enclosed within
a protective square plastic cover.
As on a cassette tape, only a small exposed portion of
the magnetic recording surface is sensitive. Avoid touching the few small portions that are
not covered
by the protective cover. Also, never try to remove this cover. Unlike the
paper jacket, the plastic diskette cover
is intended to remain on permanently.
Next, notice the notch on one side
of the diskette (it may be covered by a piece of
tape). This notch is called the write-protect notch. When it is covered with the opaque tape
packed with blank diskettes, the disk drive cannot change the contents
of that diskette.
Never remove the tape on the Test/Demo diskette.
At least two other parts of the diskette are worth mentioning: The hub and the access
slot. The hole
in the center is called the hub, A cone-shaped spindle fills it when the drive
door
is closed, and its edges are clamped. This keeps them from slipping, when the
diskette spins
at 300 RPM in use.
The oval opening in the diskette opposite the label
is called the access slot. It exposes
just enough
of the diskette's surface for the read/write head and load pad inside the drive
to touch a one inch long line from the center to the edge
of the diskette's working surface.
The bottom side
of that slot is where all the information is written as the diskette spins.
To insert a diskette. first open the drive door
by rotating the door lever counter-
clockwise one quarter
tum until it stops, with the lever level with the slot in the front of
the drive.
WRITE
PROTECT
NOTCH
WHEN COVEREO,
DISKETTE
CONTENTS CANNOT BE
AL TERED
Figure 4. Position for Diskette Insertion
9
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Grasp the diskette by the side opposite the large oval access slot, and hold it with the
label up and the write-protect notch to the left (See Figure 4). Now insert the diskette
by
pushing it straight into the slot, the access slot going in first and the label last. Be sure the
diskette goes
in until it stops naturally, with no part showing outside the drive, but you
shouldn't have to force
or bend it to get it there.
With the diskette
in position, seat it properly for use by twisting the door lever
clockwise one-quarter turn. vertically over the slot until
it stops. If it does not move
easily, stop' You may have put the diskette
in the wrong way, or incompletely. If that
happens, reposition the diskette until the door lever cluses easily.
SAFETY RULES FOR DISKETTE CARE
I
.. Keep the disk drive and its diskettes away from all moisture, dust, smoke, food, and
magnets (including the electromagnets in telephones and TV's). Also keep them away
from temperatures either too hot or too cold for you
to work in for extended periods.
2. When not in the drive, diskettes should be stored upright inside their paperjackets. Do
not allow them to become bent or folded. Since the working part
of the diskette is on
the bottom, never set
it down on a table top or other place where dust or moisture
might affect it, and
be especially careful to keep your fingers away from the openings
in the diskette cover.
3. Although some people sell kits intended to "double your diskette's capacity" by
cutting
an extra write-protect notch into a diskette, it is best not to use the other side of
the diskette on the 1551 drive, even if your diskette is labeled "double-sided." Doing
so will cause added wear
to your diskettes and drive, and may cost you an important
program some day.
4. When buying diskettes, you may use any good quality 5'/4 inch diskette.
5. Although the hub assembly will correctly center most any diskette, it would
be very
difficult to rescue data from a diskette recorded with its hub off-center.You can make
it easier for the drive to center a diskette on the spindle by buying diskettes that come
with reinforced hubs. These hard plastic rings around the hub opening make the
diskette hub more rigid, and easier to center properly.
6. Always remove diskettes before turning a drive off or on.
If a diskette is in place and
the door closed at power on
or off, you could lose part or all of the data on that
diskette.
7. Similarly, do not remove a diskette from its drive when the red drive activity light
is
on. That light only glows when the drive is actually in use. Removing the diskette with
it on may result
in your losing information currently being written to the diskette.
USING PACKAGED PROGRAMS
To use prepackaged BASIC programs available on diskette, here
is the procedure:
After turning on your computer system, carefully insert the preprogrammed diskette
as described previously. For purpose of demonstration, use the Test/Demo diskette
included with the disk drive. The following command will load a program from the
diskette into the computer:
10

DLOAD "program name"
Example: DLOAD
"HOW TO USE"
After each command press the RETURN key
The exact name
of the program you want to load is placed between quotation marks.
After you type
in the command and press the RETURN key, the following will
appear on the screen:
SEARCHING FOR
"HOW TO USE"
LOADING
READY.
•
When the word READY and the flashing cursor reappear on the screen and the red
light goes off on the drive, the program named
"HOW TO USE" on the Test/Demo
diskette
has been loaded into the computer's memory. To use it, just type the word RUN
and press the RETURN key.
If a program isn't written
in BASIC, it may require a different loading method,
which may be indicated
in the instructions that accompany the program package. The
format for that command is:
LOAD "Program name", 8, 1 (press RETURN)
This command
is used for machine language programs, which are covered in more
detail later.
At this point, however, try this command if a program doesn't load properly
using the other command.
IMPORTANT NOTE:
Throughout the rest of this manual, when the format for a command is given,
anything that
is capitalized must be included as is when you type in the command.
Anything
in lower case is more or less a definition of what belongs there. For
instance,
in the format for the HEADER command given below, the word
HEADER, the capital I
in lid, the capital D in Ddrive #, and the capital U in
Udevice # must all be typed-in as is.
On the other hand, diskette name tells you that you must enter a name for the
diskette, but it
is up to you to decide what that name will be. Also, the id in lid is
left to your discretion, as are the drive # in Ddrive #, and the device # in Udevice
#. Be aware, however, that there are certain limits placed on what you can use. In
each case, those limits are explained immediately following the format.
Also be sure to type in all punctuation exactly where and how
it is shown in
the format.
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HOW TO PREPARE A NEW DISKETTE
A diskette needs a pattern of magnetic grooves in order for the drive's read/write
head to
find things on it. This pattern is not on your diskettes when you buy them, but you
can use the HEADER command to add it to a diskette. Here
is the procedure:
FORMAT FOR THE HEADER COMMAND
HEADER "diskette
name" ,Iid,Ddrive #,Udevice #
Where:
"diskette
name" is any desired name for the diskette, up to 16 characters long (including
spaces);
"id" can be any two characters as long as they don't form a BASIC keyword
(such
as IF or ON) either on their own or with the capital I before them; "drive #" is 0
(the
1551 assumes 0 even if you don't type it in); "device # is 8, unless you have changed
it
as per instructions in Appendix A (the 1551 assumes 8 even even if you don't type it in).
Note to Advanced Users:
The
"id" cannot be a variable. For example, "A$" can be used, but the id would
be the letter
"A" and the dollar sign, not the contents of the variable. Ifyou need a
variable id, use the following command:
OPENI5,8,15:PRINT#15, "NO:MY DISK," +A$:CLOSEIS
where A$
is a two character string variable.
The chattering or thumping noise you hear just after the HEADER command begins
is entirely normal. The drive must be sure it is at track I, which it assures by stepping
outward
4S times (on a 35 track diskette). The noise you hear is the head assembly hitting
the track 1 bumper after its inevitable arrival.
After you have once formatted a particular diskette, you can re-format
it at any time,
using the above procedures. However, you can also change its name and erase its
programs more quickly and easily
by omitting the ID number in your format command.
By leaving off the lD number, the format command will finish
in a few seconds instead of
the usual 90 seconds.
ORGANIZING A DISKETTE LIBRARY
Though you may not believe it now, you will eventually have dozens, if not hundreds
of diskettes. You can ease life then by planning now. Assign each diskette a unique lD
number when you format it. There are diskette cataloging programs you can buy, that
store and alphabetize a list
of all your file names, but are of limited value unless your
diskette ID numbers are unique.
At least two valid approaches are used in assigning ID numbers. One starts at 00 with
the first diskette, and continues upward with each new diskette, through 99, and then
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