INTRODUCTION TO THE HP 85 AND THE HP SERIES 80 COMPUTERS
by Eric Bal
THE HP 85
My First Computer
My first personal computer was an HP85, which I discovered was for sale
by virtue of an ad in the "Want Ad Press" which circulated locally.
I recall driving home after the purchase was consumated at the house of
the seller, with the HP85 resting on the front car seat next to me, and I remember
worrying that the vibrations from driving over the railroad tracks might damage it.
I was that much of a novice.
But I quickly learned to program using the built-in HP BASIC language, and was writing
accounting and database programs, and wonderful graphics programs. Although I migrated
to HP's Series 200 computers, and later to HP's Series 500 model 520, learning Rocky
Mountain Basic which was a superset of the HP-85's HP BASIC, I never lost my appreciation
of the capabilities of the HP85. So let me share an overview of my perspective on the
HP85's unique wonders.
Small Integrated Form
The HP Series 80 Computers began in the summer of 1980 when Hewlett Packard
introduced the HP85 which had built into its marvelously integrated small form
factor everything needed: a keyboard with many special keys, a high resolution
alphanumeric and graphics CRT, a fast bi-directional thermal printer, and tape
cartridge drive for mass storage. The first thing that would impress you with the HP85
was its comfortable low profile size and completely integrated design.
Quiet
But when you turned it on, the next thing that impressed
you was that it was so quiet. The were no fans, no spinning discs, no discernable motors
running. When it operated it made absolutely no discernible noise giving it a subtle magical
quality. To get some idea as to how Hewlett-Packard engineered the HP85 to be so quiet
select and read the article labelled "Series 80 CPU architecture" in the scroll selection
box of the previous webpage.
Live Keyboard and Display
The next thing that would impress you was its live keyboard and screen. If you typed
the arithmetical expression 4 + 5 anywhere on the screen (as long as nothing else was
on the line) and pressed the END LINE key, the answer, in this case 9, would appear on
the next line. This magical response occured no matter what the arithmetical
expression was.
The same live status held for assigning values to variables. If you typed A$ = "Hello"
anywhere on the screen and pressed the END LINE key, the HP85 would remember the
assignment, so that if you later typed $A anywhere on the screen and pressed END LINE
the character string "Hello" would appear on the next line. In general you could do
command line programming directly on any part of the screen.
The HP BASIC Operating System
If you were attracted to these amenities, you'd be thrilled to discover the best was yet
to come. The HP85 had its operating system built as firmware directly in ROM and when
you turned this machine on it came up intelligent. The operating system was the HP BASIC
langiage operating system, which was an intuitive and powerful language that was easy to
learn and remarkable in its capabilities.
To program you could use the full screen for editing. If you typed in the program
10 FOR I = 1 TO 999
20 DISP I
30 NEXT I
40 END
and then pressed the RUN key, you would immediately see the numbers from 1 to 999
printing and scrolling past you on the screen. And if you replaced the DISP command with
the PRINT command then the thermal printer would print the output.
The I/O capabilities of HP BASIC, both the power of the command set and the simplicity and
intuitiveness of the syntax, caused the HP85 to become a mainstay in research and manufacturing
labs thoughout the world, as an instrument controller and for data collection and analysis.
The HPIB interface module could be plugged into one of the four rear ports of the HP85 and
allowed the HP85 to be connected to many devices simultaneously, but with the
ability to address each indiviual device programmatically.
The HP85's built in 16K RAM was effectively more than 16K when compared to other
computers back then because the operating system, being resident in ROM, did not
consume any of the RAM. The RAM could also be doubled to 32K by a plugin module.
In the event you had programs needing more RAM then you had, the HP BASIC
operating system allowed you to chain sections of your program into RAM one at a time,
overwriting the previous section of code that was in RAM, while maintaining knowledge
of the values of the variables used by the overwritten code.
Arithmetic Precision
The HP85's operating system displayed arithmetic results with precision with up to 12 digits.
For certain applications this was a great benefit.
The Graphics Subsystem
The HP-85's CRT has separate RAM for storing an alphanumeric display and for storing a
graphics display, and the keyboard has a key to toggle between the alphanumeric screen
and the graphics screen.
The HP-85's HP BASIC language contained a number of graphics commands and
draw modes that enabled you to code programs to create an endless and amazing
variety of graphics images on the CRT. And when you found you created such an
interersting image you could save it to the tape cartridge or to a floppy or hard disc,
using a single command to save the image. And, of course, you could later download
the image to see it again, using just a single command. You could even write a program
to download a series of previously saved images, one at a time, by the press of a key or
by a timed sequence.
And when you discovered your program had created a graphics image that was worth
keeping, you could not only save it with a single command, but you could also, by pressing
a single key, print a hardcopy of the image using the built-in thermal printer (and print a
listing of the code, as a reference, right under the printed image.
Ability to Expand
Hewlett-Packard designed the HP85 to provide a rich set of expansion capabilities through
four ports built into the rear of the machine, allowing an HP85 user to extend the HP BASIC
language, to connect to various disc drives, printers and plotters, to write assembly language
programs, to emulate other operating systems, and to use different programming languages,
and to do much more.
--back--