A (Very Squashed!) History of Personal Computer

Ancient History

In order to really understand where the personal computers of today came from, it is important to an overview of the history of computing in general.

Here is the very first "personal computer": the abacus! This is one of those inventions that seem to be so old and so common that it is hard to tell where it was first invented. The first one might have appeared 5000 years ago in Babylonia (now Iraq). Major improvements occurred in Egypt. Later, the Chinese developed the most common current form around 1200AD.

While many of us are probably used to thinking of this as a child's toy, it turns out that the device is quite versatile--you can add, subtract, multiply, and divide. A clever person can even do square and cube roots! They are still commonly used today in the Far East.

(For more on the abacus and abacus math, see http://www.ee.ryerson.ca:8080/~elf/abacus/intro.html)

Another major development occurred in the west around 8th and 9th centuries AD (AD 700's and 800's). This was the introduction of Arabic numerals, which included the concept of "base 10" counting and the zero. Prior to this everybody in Europe used Roman numerals (I, II, III, IV, V, VI, etc.). Arabic numbers made math easier to do; the Roman system did not work very well even for simple addition and subtraction. (And just try doing long division with Roman numbers sometime! It is possible, but very cumbersome.)

(For more on the differences between doing arithmetic with Arabic and Roman numbers, see http://www.jimloy.com/arith/division.htm )

By the 1600's we see early mechanical calculators appearing in Europe. Perhaps the best known was developed by mathematician and philosopher Blaise Pascal, who as a young man spent three years inventing one to help his father do his taxes. Unfortunately, it did not catch on because it tended to jam and was difficult to repair.

One of Blaise Pascal's early calculating machines.

An extremely famous attempt was executed by Charles Babbage, an Englishman, in the early 1800's. His "Difference Engine" was a huge steam-powered mechanical calculator. Though never completely finished, this device did mechanically much of what today's computers do electronically. Unfortunately his work was neglected in his own day, making him one of those interesting "what might have been's."

Enter Electronics

The first electrical/electronic calculator was invented around 1941 by Konrad Zuse, a German engineer. He built several different models, including the Z1, Z2, and Z3. However, he was unable to convince the German government (the Nazi's) to support his work.

Picture of the Z-1, the first electronic computer. It was destroyed by the Allies in a bombing raid early in WWII.

As a result, computing advanced more rapidly in England and the United States . The British built Colossus, used in 1943 for code breaking, while ENIAC was built in Maryland in 1945, for use with ballistics computations.

ENIAC. The machine contained 18,000 vacuum tubes, making it rather unreliable!

These computers were pretty much one-of-a-kind units. However, by 1951 we see UNIVAC introduced, a machine sold commercially by Sperry-Rand (now a part of Unisys). 48 of these units were manufactured.

UNIVAC

In 1964 IBM started marking the IBM 360 line of computers, a fabulously successful series which pretty much set the standard for computing for the next twenty years. The main control unit was roughly the size of a small car, with most communication taking place through teletype machines. Large scale memory storage used hard drives in machines the size of washing machines or refrigerator-sized magnetic tape readers--much like the ones you see in old science fiction movies! IBM was actually known for having large, relatively inexpensive hard drives; in 1973 you could buy a 400 MB unit for about $111,600. A machine like this could cost $100,000 to a $1,000,000, depending on features, and fill up a large room.

Interestingly, as time and technology progressed the machines shrank only moderately. Most of the advances came in the form of increased speed and memory--the core computer architecture stayed the same. But from IBM's perspective, why change it? They were getting about 100 orders for these expensive machines a month, and were pulling in billions of dollars in revenue. (In fact, the four main computers on the space shuttle are basically miniaturized versions of these computers! The main difference is in size and weight; they weigh in at only 65 pounds each.) 

So now you have more powerful machines that do the same job faster than before. Instead of shrinking the machine, people instead began using timesharing. People would contact the computer from a remote station using some sort of computer terminal. This way many people could share the same expensive computer at once. Even better, it meant that you did not have to be right in the same room as the computer. This allowed a business to purchase one computer and have branch offices dial in. Or, small businesses or colleges could purchase computer time on a machine far too expensive to afford individually.

Minicomputers

The large computers that we have just described are called "Mainframes," and were large and expensive. However, not everybody wanted to, or could, use them. Hospitals, travel agencies, and mid-size businesses and universities needed computers; however, a mainframe was too large and expensive to purchase, and they might not want to transmit their data offsite for security or technical reasons. As a result, the "minicomputer" was devised. The first successful model was the DEC ("Digital Equipment Corporation") PDP-8, which sold for about $16,000. Other companies, such as Data General, Hewlett-Packard, and IBM, soon entered the market as well. These machines were smaller (about the size of a large refrigerator) and were also designed to be used with timesharing. These machines were extremely popular during the later 1970's and early to mid-1980's.

A PDP-8 series minicomputer. The device on the left side of the picture that looks sort of like a clothes drier is actually a printer and is not part of the minicomputer.

Microcomputers

Okay, so now we have looked at a few of the precursors to computers, as well as some of the "big iron." So…where did microcomputers--also called "personal computers," since they are not really designed to be used by more than one person--come from??  The answer seems to be… hobbyists and gadgeteers! But why? The answer seems to be: that all of the computer engineers knew that any computer capable of really doing anything really useful had to be big, complex, and expensive. This is not to say that they saw no market for small computing devices; HP, for example, was making programmable calculators in the mid-1970's. However, these cost about $800 and were pretty much "math only" devices aimed at professional engineers.

The HP 65 "computer," which sold for about $800 in 1973 and was more like a programmable calculator.

And in fact, the "big guys" were correct, at least at first: the first microcomputers were  pretty much in fact useless for anything except for use in a few specialized industrial devices or for use as teaching tools. A breakthrough came in New Mexico, with one Edward Roberts, Jr. Roberts was an electrical engineer who was also an electronics hobbyist who wanted to turn his hobby into a side business. He realized that the new-fangled "integrated circuits" that became common in the wake of the space program could be used to construct a simple calculator. The parts cost $100; he would box them up and sell them as a kit for $179 or, for a bit more, as assembled calculators. By 1973 his company, MITS, was churning out hundreds of them and selling calculators as fast as they could make them. However the "big guys"--especially Texas Instruments--also began selling similar units in the millions…not only to MITS' core hobbyist market, but also to the general public. Worse, by 1974 the price of a basic calculator had dropped below the parts cost for Roberts, threatening to put his calculator factory out of business.

After a couple of false starts, Roberts hit on a new idea that drew on his engineering expertise and took has calculator venture to the next level--he would build and sell a simple computer in kit form. This would play to his strength in marketing to the electronic hobbyist market, and probably NOT attract competition from the larger companies since it really couldn't do very much. He would buy his chips from Intel, who by this point had pretty much decided that microprocessor chips would never really catch on and thus gave him a big discount. The new computer kit, called the "Altair 8800," was featured on the cover of the January 1975 cover of Popular Electronics, and thousands of orders started pouring in. The kit sold for about $399.00.

The problem was that Roberts was more of an engineer that a businessman; his company filled orders slowly, and his accessories and add-on devices didn't work very well. The machine didn't even come with an operating system--instructions were entered by flipping the switches on the front of the panel, line by tedious line in machine code.

Ironically, it seems that the problems which handicapped Roberts and MITS were a boon to the new personal computer market! Roberts had never bothered to patent his design, so soon other companies were making accessories and memory upgrade boards for the computer. Indeed one company, IMSAI, copied the entire unit exactly! Also, MITS began to pay people to write programs for its machine. One of the most important of these was the computer language BASIC ("Beginner's All Purpose Symbolic Instruction Code"). While this language had been around since 1963, two young hobbyists, Bill Gates and Paul Allen, created a version that ran on the Altair 8800. They called their company "Micro-Soft."

All in all, is appears that the Altair did exactly what Roberts wanted it to do: it fascinated hobbyists, but was not useful enough to be of interest to the large computer companies. The Altair did inspire other designs for hobby computers and kits. Many were even more impractical and difficult to use than the Altair (see, for example, the KIM-1).

The KIM-1. Hobbyists could enter their code directly through the keypad on the motherboard! A monitor and keyboard could also be attached. The company that produced the KIM was later bought out by Commodore.

However a few designers dared to dream of producing a computer that could actually be used to do something useful, and perhaps even be available to the general public. Foremost among these were Steve Jobs and Steve Wozniak (aka "The Woz"). Their first computer, the Apple I, was introduced in kit form in the summer of 1976; several hundred units were sold at a price of $666.66.

	The Apple I. What you see on the left is what you got for your $666.66! However, creative people could make their own interesting enclosures...

Their follow-up unit, the Apple II series (initially released in 1977) would sell over a million units over the next ten years, and would change the face of  personal computing. (For more details about some of these old computers, see the outstanding site at http://oldcomputers.net/index.html That site was also the source of many of the pictures that I used here.)

This is an early Apple II, which probably would have sold for about $1200 in 1978 with the accessories (monitor and floppy drive) shown. While these early models could only show six colors and WRITE ALL IN CAPITAL LETTERS, the Apple IIe (introduced in early 1983) was quite useful and soon dominated the educational market.