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1541 tutorial 2
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2022-08-26
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History of the 1541 continued.
------- -- --- ---- ---------
Then came the VIC-20. Commodore
made many advances on this one! Low
price! Graphics! Low price! Color!
Low Price! 3-channel sound! Low
Price! RS-232! Low Price! 8 user-
programmable function keys! Low Price!
A cartridge slot for games! Not to
mention a low price! Even though they
were producing a computer to compete
with home video games, they learned
their lesson on the PET 2001 and gave
the VIC a REAL KEYBOARD!
But for the sake of low price, Com-
modore took several MAJOR steps back-
wards. Only 5K of RAM. 22-column
screen. Back to BASIC V2. And worst
of all, they scrapped the wonderful
IEEE-488 bus that could shove all 8
bits of a byte down the wires at once,
and replaced it with a "serial bus"
that had to spool those bits out one
at a time.
Commodore then produced the 1540
Single Floppy Disk Drive. It was bas-
ically a one-drive, serial bus version
of the 4040. It had less RAM, so that
fewer files could be open at any one
time. It used the new half-high disk
drive units. Instead of two micro-
processors (one for the drives and one
for the interface), it had one proces-
sor controlling the single drive and
the interface.
About two years later Commodore in-
vented the Commodore 64! (Ever heard
of one of those?) I won't go into
all of its nice features, but it still
had the serial bus and it still had
BASIC V2.
Well, the 1540 was supposed to work
with the 64, but it couldn't SAVE or
LOAD programs due to timing problems.
(Sound familiar?) This time, Commo-
dore upgraded the disk drive instead
of the BASIC in the computer, and so
was born the 1541. The 1541 is almost
identical to the 1540 except for the
DOS in ROM.
Anyway, with BASIC V2, it is not
easy to send commands to the disk.
You have to OPEN the command channel.
It's not easy to view the disk direc-
tory. You have to LOAD that as a pro-
gram and LIST it. (Good-bye whatever
program you were working on, unless
you saved it). If the drive gets an
error, it flashes its little red light
as a sign. If you want to know what
KIND of error, you can't just PRINT
DS$ (Disk Status) like you can with
BASIC V4.
These problems existed in the old
PETs with BASIC V2 as well, so an en-
terprising programmer by the name of
Bob Fairbairn wrote the DOS Manager,
or DOS Wedge as it has come to be
known. (Also referred to as the DOS
Support Program.) Commodore put this
goodie on the TEST/DEMO disk they in-
cluded with every drive.
So with the 1540/1541, two new ver-
sions of The Wedge were written -- one
for the VIC-20 and one for the C-64.
This program is included on your TEST/
DEMO disk, and can really make life
easier!
The manual included with the 1541
is actually a hurried revision of one
of the earlier drive's manual. (For
proof, just read the description of
Error #74 "DRIVE NOT READY" on page 46
thereof! Not to mention the "red-
light/green-light" mixup on page 8!)
As a reference manual for techni-
chal-types, the 1541 manual isn't half
bad. As a tutorial manual for the
first-time computer user, it's a joke!
So all this history has been lead-
ing up to this announcement: Start-
ing next month, LOADSTAR will publish
an on-going 1541 Tutorial! We will
cover basic operations and the DOS
Wedge first, then move on into sequen-
tial and relative file handling, and
later into more esoteric functions.
For now, a few do's and don'ts. I
won't tell you why (yet!), but just
observe the following.
1. DO NOT use the "Save and Re-
place" command described on
page 13. Believe me, it can
be as unlucky for you as the
page number implies!
2. DON'T use the "Open and Re-
place" construct described on
page 20. Just don't!
3. DO NOT turn on or off either
the computer or the drive if
there is a disk in the drive
and the door is closed. Pop
the door open first!
4. DO make sure that all your
disks have different ID's.
5. DO plug all components of
your computer system into
the same GROUNDED 3-wire
power circuit. In fact, in-
vest in a power strip!
Next month, I'll cover LOADing and
SAVEing, and Formatting a new blank
disk. See you then!