The Altair 8800 Computer

AlTAIR 8800 COMPUTER IXDS5503 - Media History and Theory Professor: Jason Occhipinti Anthony Moore May 1, 2015

FROM WAREHOUSE TO DESKTOP The Harvard Mark I was big. More than 50 feet long and weighing in at nearly five tons, it was the brainchild of Howard Aiken, a Harvard graduate student who in 1937 proposed what would become the largest electromechanical calculator ever built.

Officially known as the Automatic Sequence Controlled Calculator, the Mark I consisted of 78 adding machines and calculators linked together with mechanical counters, paper-tape-fed sequencers and card readers. And when IBM completed construction of the machine in 1944, it was the model of what computing hardware should be: a huge calculator for solving huge problems. [1] Two years later, the Mark I was dwarfed by the ENIAC, an electronic computer weighing 30 tons and requiring 1,000 square feet of floor space. In 1948, a different Mark I computer at the University of Manchester in England, the first computer to run stored programs, required a medium-size room. And in 1951, MIT's Whirlwind, the first real-time computer, took up more than 2,500 square feet. [2] Physics and business requirements demanded that smaller, not bigger, computers be developed.

By the time IBM announced its System/360 mainframe line in 1964, computers had stopped growing.

In 1965, Digital Equipment Corp. had trimmed a system down to a single-cabinet minicomputer, the PDP-8. And in 1968 Data General Ed Roberts and the Altair 8800 (Image 1) Nova’s minicomputer could sit on a tabletop. With the exception for the Cray-1 supercomputer, which was introduced in 1976, large computers would spend the next few decades shrinking into smaller rectangular cabinets. The shape of things to come; however, would belong to desktop computers, which arrived in 1975 with the Altair 8800. [3]

AlTAIR 8800

IXDS5503 - Media History and Theory · Moore

1

The Altair 8800 was developed by Ed Roberts, the founder of Albuquerque based Micro Instrumentation and Telemetry Systems (MITS), a company originally set up to sell electronics kits to model rocket hobbyists. The company went on to sell electronic calculator kits, but was soon overshadowed by bigger firms.

In the mid-1970's, with the firm struggling with debt, Roberts began to develop the Altair 8800 kit for hobbyists which was operated by switches with no display monitor. [4] Roberts wanted to make sure the machine he was building was a full computer. Later, he explained: "The basic ground rules for a personal computer from a technical standpoint is that it had to be a real, fully operational computer that was fully expandable and at least in principal could do anything that a general purpose minicomputer of the time could do. 'Minicomputer' was the term then and referred to any 16-bit or 8-bit machine. And, those were the ground rules. We wanted to make a machine that January 1975 Edition of Popular Mechanics. The article that was, from a user's stand-point, not degenerative at all. The main began the PC revolution (Image 2) difference between our machine and where others were is that we used microprocessors, and everything was the latest state of the art. We never used core memory even though we did look at core. At the time we began work on the Altair, core memory was still significantly cheaper than IC based memory." [5] MITS sold the microcomputer by mail order through advertisements in Popular Electronics, Radio-Electronics and other hobbyist magazines. Both kits and fully

2

AlTAIR 8800

IXDS5503 - Media History and Theory 路 Moore

assembled machines (for an extra $100) were available. [6] The Altair kit included only the parts to build a case, power supply, an 18-slot card cage (with four slots available), an Intel i8080-based CPU card, and a memory card with 256 bytes of memory, the best you could do was make the lights blink in certain patterns. The case was painted robin's egg blue, inspired from the color used by IBM in the early 1970's on its mainframe computers, so as to convey that, yes; the Altair was a "real" computer. [7]

THE REVOLUTION No one had realized just how primed the market was for a personal computer. The 1975 January issue of Popular Mechanics signaled to thousands of electronics hobbyists, programmers, and other technology enthusiasts that the era of the personal computer had finally arrived. Within a week of the story appearing, MITS had 200 orders, and by the end of February, it had 2,000 order.

Even those who didn’t purchase the Altair saw the Altair article as a sign that they could now have their own computers. The Altair was the fruit of a technological revolution that dropped straight into the hands of a hungry population. [8] Bill Gates Demonstrates his BASIC interpreter on the Altair 8800 (Image 3)

Among the enthusiasts whose imagination was taken by this edition of Popular Mechanics was a Harvard University undergraduate named Bill Gates, and his good friend Paul Allen. The two contacted Roberts to write a BASIC language interpreter for the machine. Roberts showed interest in their proposal, but unwittingly did not know that Gates and Allen had no BASIC software, as of yet, to offer. The two started work on their BASIC interpreter, using a self-made simulator for the 8080 processor on a PDP-10 minicomputer. They figured they had only several weeks before someone else beat them to the punch.

AlTAIR 8800

IXDS5503 - Media History and Theory · Moore

3

Once they had a version working on the simulator Allen flew to MITS in Albuquerque to deliver the program on paper tape. The first time the program was run, it displayed “Altair Basic” and then crashed. The next day, Allen returned with a new paper tape but this time Altair BASIC ran successfully. The first program ever typed in was “10 print 2+2” and after typing “run” it displayed the correct answer: “4”. Allan was offered a position by Roberts as the Director of Software and the only member of the software department. Gates, who was then still a student, started working for MITS part-time after he left school. [9] The Altair was not only considered the first personal computer but was a launching pad for the software company Microsoft.

MITS started work on its own peripheral cards, including interfaces to peripherals and more memory, which the machine desperately needed.

Other companies became involved too, starting with Process Technology which began creating plug-in boards, such as more memory, a way to connect it to a teletype, and later, ways The Altair 8800 connected to a teletype machine (Image 4) of hooking it to a television set and a keyboard. The machine continued to attract a lot of attention in the hobbyist community. On April 16, Steve Dompier reported on MITS at the Homebrew Computing Club in Menlo Park, CA, saying that MITS had 4,000 orders. Homebrew Computer Club members started to create machines of their own, including Homebrew member Steve Wozniak, who would soon build his Apple I. [10] Aside from Microsoft and Apple, the release of the Altair computer generated dozens of other companies. [11]

4

AlTAIR 8800

IXDS5503 - Media History and Theory · Moore

PROGRAMMING THE ALTAIR According to the Popular Mechanics article, the Altair could be programmed by varying the hardware. This was accomplished through a series of switches on the front panel that could be positioned either on or off (1 or 0.) For example, when the pattern 10000010 set by the switches and received by the Altair it instructed the computer to add. By setting address and data switches, a complete program of up to 78 steps could be inserted into the processor. If extensive programming was to be performed,

Front panel switches of the Altair 8800 (Image 5)

an assembler or higher language was needed. The article boasted thousands of applications for the Altair which included a programmable scientific calculator, sophisticated intrusion alarm system, auto-pilot for planes and boats, navigation, timeshare computer system and a brain for a robot. [12] To promote interests, the article came with step-by-step instructions on how to add two numbers together.

AlTAIR 8800

IXDS5503 - Media History and Theory 路 Moore

5

Adding two numbers together was accomplished in the following manner. First, the Altair RESET switch was positioned to 0, clearing the memory. Next, the first number was entered in an eight-bit pattern and the DEPOSIT switch was pressed to load the number into memory. Next one would enter the next eight-bit command and press the DEPOSIT NEXT switch which would load that number/instruction into the next available memory address. Each of the settings could be reviewed by using the EXAMINE switch and finally RUN to execute the code. [13]

THE “BEGINNINg” By the end of 1975, one could build a CPU with add-in boards for a little over $1,000, and one could attach a terminal and printer, run Basic, Assembler, and a Debugger.

Also by that time, there were direct competitors, including Imsai Manufacturing Corp., which had its own machine based on the 8080 processor. [14] As for MITS, it did $1 million in sales in 1975 and tripled that in 1976 “Our market was bigger than our capacity to expand” Roberts said. When he sold the company in May 1977, Roberts indicated it was doing $20 million in business annually. The future owners of MITS proved unable to market the Altair line in an increasingly competitive industry and discontinued the line a couple of years later. Roberts moved to Georgia to become a doctor, passing away in 2010. But the impact of the Altair lives on; it was the machine that convinced a large number of hobbyists that the time was right for a personal computer and that here was a machine they could actually own. Over the life of the Altair, it sold tens of thousands of units, making it the first volume commercial microcomputers; the computer revolution was on. [15]

6

AlTAIR 8800

IXDS5503 - Media History and Theory · Moore

FOOTNOTES [1] Hayes, F. (2002). The Story So Far. Computerworld, 36(47), 30.

[2] Hayes, F. (2002).

[3] Hayes, F. (2002).

[4] “Microsoft founders lead tributes to ‘father of the PC’”. BBC News. April 2, 2010.

Retrieved April 16, 2015.

[5] Miller, Michael J. The Altair 8800: The Machine that Launched the PC Revolution.

December 19, 2014. Retrieved April 18, 2015.

[6] “The Altair 8800 of Ed Roberts”. History of Computers. Retrieved April 18, 2015.

[7] Cini, Richard A. “Brief History of the Altair”. MITS Altair 8800 Computer. Retrieved April 18, 2015.

[8] Freiberger, P., Swaine, M. Fire in the valley: the making of the personal computer.

Osborne/McGraw-Hill. 1984.

[9] “The Altair 8800 of Ed Roberts”. History of Computers. Retrieved April 18, 2015.

[10] Miller.

[11] Levy, S. (2007). Power to the People. Newsweek, 150(13), 46-50.

[12] Worlds First Minicomputer Kit to Rival Commercial Models... “Altair 8800”. Popular Electronics. January 1975.

[13] “Altair 8800 Operator’s Manual”. MITS Inc. 1975. Retrieved April 18, 2015 [14] Miller.

[15] Miller.

AlTAIR 8800

IXDS5503 - Media History and Theory · Moore

7

RESOURCES DESPOSITO, J. (2012). PAUL ALLEN: SHARP PROGRAMMING AND SHREWD DEALS GUILD AN INDUSTRY TITAN. Electronic Design, 60(15), 46.

Ed Roberts. (2010). Times, The (United Kingdom), 59.

Rosenberger, J. (2010, June). PC Pioneer Ed Roberts, 1941-2010. Communications of the ACM. p. 14.

IMAGES Cover Image: http://oldcomputers.net/altair-8800.html Image 1: http://www.thocp.net/hardware/altair.htm Image 2: http://www.digibarn.com/collections/mags/pe-jan-1975/ Image 3: https://www.youtube.com/watch?v=pqAg0GJLPGk Image 4: http://sysmagazine.com/posts/166369/ Image 5: http://www.giorgiosancristoforo.net/2015/02/16/music-with-the-first-pc-everthe-ultimate-8-bit-machine/

8

AlTAIR 8800

IXDS5503 - Media History and Theory 路 Moore