Personal Computer History

Personal Computer History

In order to properly understand and appreciate the progress we have made and to anticipate the continued evolution of the industry, let’s look at the progress of the computer. What precisely is a computer? Machines that helped people do computation have been around for almost 150 years (Brigham Young invented a device to calculate the number of miles a wagon traveled by counting the number of wheel rotations). There have been all types of machines built to compute or measure various things (there’s even one that will compute a logarithm).

Most of these machines are “analog” or value-based. So they can represent any value between zero to one equally as well as zero to a million. An example of an analog device is the odometer on your car (please note that these may not be true analog, but the concept
still holds). Whether you move the car one inch vs. one thousand miles, it makes little difference—your car still retains the distance, thus further depreciating it’s value.

There was another type of machine which used a magnet-powered switch which would close the switch when the electromagnet was turned on (this kind of switch is a “relay”). Telegraph used crude relays. The advantage of using switches (either “on” or “off”—called “digital”), the results would always be predictable (the value will always be zero or one). Analog devices always have to be tuned (just try to put a different sized tire on your car). The problem with relays is the power required and delay experienced was too great to make them into a computational device. Early computers went a different route by using electron (or vacuum) tubes.

Vacuum tubes have been used for power amplifiers, but they could also be used as switches as well and would function many times faster than the relays would. The idea was pretty simple: the tube had three plates. The first plate was the source power, the second was the destination, and the third was the “switch.” The electrons would at the source would gather but would not be able to get to the destination unless power was applied to the “switch-plate.” Think of it like having scuffed your feet on the floor to generate static electricity then getting close to something (or someone) you want to zap— still they’re too far away. You need something to close the gap. That’s something like what the “switch plate” does.

Memories and calculations were held and completed by turning on and off thousands of these switches

However, vacuum tubes still required tons of equipment and megawatts of power. The proverbial add/subtract/multiply/divide calculator on your wrist used to take up an entire building floor and require many megawatts.

In the mid 1950s, a special little switch was invented that has thus reshaped our history: the transistor. The power (no pun, honestly!) in this little thing was it’s size (less than . 1”—compared to 3-4” for a vacuum tube) and its power (much less than a watt—compared to 5-10 watts)

Modern computers are composed of millions and millions of these transistors switches. Like the vacuum tubes, the transistors are arranged in arrays to accomplish what we ask of them. Your computer memory alone has millions of transistors—one megabyte has one million bytes or eight million bits. That’s more than 8,000,000 transistors!

Personal computers have been around as early as the mid-1970s. The companies involved include Apple, Commodore, Atari, Synclair, to name a few. The first chips for these computers only had 10-50 thousand transistors. At the time personal computers were not taken seriously and were infrequently found in the workplace.

The first attempt to make a business-directed personal computer was by Apple when they introduced the Lisa computer. That was a failure—mostly do due to the $7000 price tag. The next was the Macintosh which was better received. The growth of personal computers did not really take off until IBM entered the market. From their open architecture, hundreds and thousands of computer companies sprang up. All the while technology advanced at a tremendous rate. Also, due to advances in chip manufacturing, the prices plummeted.

Share this post

Post Comment