As is true of so many facets in computing, the term “Personal Computer” can be something of a slippery customer. Why not take a moment to ponder what this term means to you before you leap headfirst into the following discussions …

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Before the Real Personal Computers
There were a number of contenders for the title of “Personal Computer” before the machines that we now think of in this context appeared on the scene. For example, the IBM 610 Auto-Point Computer (1957) was described as being “IBM’s first personal computer” on the premise that it was intended for use by a single operator, but this machine was not based on the stored program concept and it cost $55,000!

Other contenders include MIT’s LINC (1963), CTC’s Datapoint 2200 (1971), the Kenbak-1 (1971), and the Xerox Alto (1973), but all of these machines were either cripplingly expensive, relatively unusable, or only intended as experimental projects. Thus, for the purposes of these discussions, we shall take the position that the term “Personal Computer” refers to a reasonably affordable, general-purpose, microprocessor-based computer intended for the consumer market.

The Micral
Given that the 8008 was not introduced until November 1972, the resulting flurry of activity was more than impressive. Only six months later, in May 1973, the first computer based on a microprocessor was designed and built in France. Unfortunately the 8008-based Micral – as this device was known – did not prove tremendously successful in America. However, in June of that year, the term “microcomputer” first appeared in print in reference to the Micral.

The Scelbi-8H
In the same mid-1973 time-frame as the Micral made its debut, the Scelbi Computer Consulting Company presented the 8008-based Scelbi-8H microcomputer, which is now recognized as being the first microprocessor-based computer kit to hit the market (the Micral wasn’t a kit – it was only available in fully assembled form). The Scelbi-8H was advertised at $565 and came equipped with 1 K-byte of RAM.

The Mark-8
In June 1974, Radio Electronics magazine published an article by Jonathan Titus on building a microcomputer called the Mark-8, which, like the Micral and the Scelbi-8H, was based on the 8008 microprocessor. The Mark-8 received a lot of attention from hobbyists, and a number of user groups sprang up around the US to share hints and tips and disseminate information.

The Altair 8800
Around the same time that Jonathan Titus was penning his article on the Mark-8, a man called Ed Roberts was pondering the future of his failing calculator company known as MITS (which started in a garage and ended up being located next to a laundromat in Albuquerque, New Mexico). Roberts decided to take a gamble with what little funds remained available to him, and he started to design a computer called the Altair 8800. Roberts based this system on the newly released 8080 microprocessor, and the resulting do-it-yourself kit was advertised in Popular Electronics magazine in January 1975 for the then unheard-of price of $439. (The authors don't have the faintest clue why the Altair 8800 wasn't named the Altair 8080, but they would be delighted to learn the answer to this conundrum if anyone out there knows.)

In fact, when the first unit shipped in April of that year, the price had fallen to an amazingly low $375. Even though it contained only a miserly 256 bytes of RAM and the only way to program it was by means of a switch panel, the Altair 8800 proved to be a tremendous success. (These kits were supplied with a steel cabinet sufficient to withstand most natural disasters, which is why a remarkable number of them continue to lurk in their owner’s garages to this day.)

As a point of interest, when Roberts first contacted the folks at Popular Electronics magazine and persuaded them to do a cover story on his machine, they not surprisingly asked him for the name of the little scamp. This somewhat stumped him, so he asked his daughter for her advice as to a moniker that sounded sufficiently “high-tech.” She suggested Altair, which was the name of a star system in one of the Star Trek episodes, and thus was a legend born.

For the more pedantic amongst us, this was Star Trek Episode #34 entitled Amok Time, which first aired on the 15th September, 1967. The writer of this episode was Theodore Sturgeon; the director was Joseph Pevney; and the guest stars were Arlene Martel as T’Pring, Celia Lovsky as T’Pau, Lawrence Montaigne as Stonn, and Byron Morrow as Komack.

Yes we know, we know … Altair was also the scene of the action in the classic Sci-Fi film Forbidden Planet (1956), which has been described as “Shakespeare and Freud collide under the green skies of Altair IV.”

As one final point of interest, Roberts sold MITS in 1977, completed medical school, and set up practice as a small town doctor.

The Birth of Microsoft
Also in April 1975, Bill Gates and Paul Allen founded a little company called Microsoft (which was to achieve a certain notoriety over the coming years), and in July of that year, MITS announced the availability of BASIC 2.0 on the Altair 8800.

This BASIC interpreter, which was written by Gates and Allen, was the first reasonably high-level computer language program to be made available on a home computer – MITS sold 2,000 systems that year, which certainly made Ed Roberts a happy camper, while Microsoft had taken its first tentative step on the path toward world domination.

The Kim-1
In June 1975, MOS Technology introduced their 6502 microprocessor for only $25 (an Intel 8080 would deplete your bank account by about $150 at that time). A short time later, MOS Technology announced their 6502-based KIM-1 microcomputer, which boasted 2 K-bytes of ROM (for the monitor program), 1 K-byte of RAM, an octal keypad, a flashing LED display, and a cassette recorder for storing programs. This unit, which was only available in fully-assembled form, was initially priced at $245, but this soon fell to an astoundingly $170.

The Sphere 1
The introduction of new microcomputers proceeded apace. Sometime after the KIM-1 became available, the Sphere Corporation introduced its Sphere 1 kit, which comprised a 6800 microprocessor, 4 K-bytes of RAM, a QWERTY keyboard, and a video interface (but no monitor) for $650.

The Apple I and Apple II
In March 1976, two guys called Steve Wozniak and Steve Jobs (who had been fired with enthusiasm by the Altair 8800) finished work on a home-grown 6502-based computer which they called the Apple 1 (a few weeks later they formed the Apple Computer Company on April Fools’ Day).

Although it was not tremendously sophisticated, the Apple 1 attracted sufficient interest for them to create the Apple II, which many believe to be the first personal computer that was both affordable and usable. The Apple II, which became available in April 1977 for $1,300, comprised 16 K-bytes of ROM, 4 K-bytes of RAM, a keyboard, and a color display. Apple was one of the great early success stories – in 1977 they had an income of $700,000 (which was quite a lot of money in those days), and just one year later this had soared tenfold to $7 million! (which was a great deal of money in those days).

The Commodore PET and the TRS-80
Also in April 1977, Commodore Business Machines presented their 6502-based Commodore PET, which contained 14 K-bytes of ROM, 4 K-bytes of RAM, a keyboard, a display, and a cassette tape drive for only $600.

Similarly, in August of that year, Tandy/Radio Shack announced their Z80-based TRS-80, comprising 4 K-bytes of ROM, 4 K-bytes of RAM, a keyboard, and a cassette tape drive for $600.

One point that may seem strange today is that there were practically no programs available for these early machines (apart from any programs written by the users themselves). In fact, it wasn’t until late in 1978 that commercial software began to appear for personal computers.

Possibly the most significant tool of that time was the VisiCalc spreadsheet program, which was written for the Apple II by a student at the Harvard Business School and which appeared in 1979. It is difficult to overstate the impact of this program, but it is estimated that over a quarter of the Apple machines sold in 1979 were purchased by businesses solely for the purpose of running VisiCalc. In addition to making Apple very happy, the success of VisiCalc spurred the development of other applications such as word processors.

When home computers first began to appear, existing manufacturers of large computers tended to regard them with disdain (“It’s just a fad ..... it will never catch on”). However, it wasn’t too long before the sound of money changing hands began to awaken their interest. In 1981, IBM launched their first PC for $1,365, which, if nothing else, sent a very powerful signal to the world that personal computers were here to stay.

Many people refer to IBM affectionately as “Big Blue”, but for some reason IBM never bothered to trademark this sobriquet. In 1995, another enterprising company did just that, which probably caused a certain amount of consternation in the corridors of power!

Unfortunately, we’ve only been able to touch on a few systems here, but hopefully we’ve managed to illustrate both the public’s interest in – and the incredible pace of development of – the personal computer. The advent of the general-purpose microprocessor heralded a new era in computing: microcomputer systems small enough to fit on a desk could be endowed with more processing power than monsters weighing tens of tons only a decade before.

The effects of these developments are still unfolding, but it is not excessive to say that electronics in general – and digital computing and the personal computer in particular – have changed the world more significantly than almost any other human inventions, and many observers believe that we’ve only just begun our journey into the unknown!

Note: The material presented here was abstracted and condensed from The History of Calculators, Computers, and Other Stuff document provided on the CD-ROM accompanying our book How Computers Do Math (ISBN: 0471732788).