Many people have seen only the personal computer and are unaware of some of the developments that were made over the years. It's both interesting and instructive to see what early computers looked like. Here's a small collection of images from the past. If you'd like more try to find a copy of "Bit by Bit: An Illustrated History of Computers" by Stan Augarten. This was published in 1984 by Ticknor and Fields. It is out of print but you can probably find a copy by checking with a used book service on the 'net. Click on any of the images below to see a larger version of the picture.
Stonehenge on Salisbury plane in England is probably the first computer. It dates from about 1800-1400 BC. It was used to predict astronomical events and perhaps also served some religious purpose. The alignment of the stones relative to the sun constituted it's program and the sun's position relative to the stones provided the output.
The International Standards Organization (ISO) began it's work on the Open Systems Interconnect (OSI) model around the time of Stonehenge. Here's a view of their first headquarters and an early draft of the OSI model specification:
Blaise Pascal developed a mechanical calculator in the 1650's that automated addition and subtraction. This is a simple mechanism with gears. It is operated by rotating the small wheels and the answers appear in windows above them. The first image is of a historic model while the second image is from a modern model. The latter isn't terribly practical but it does illustrate how this early mechanical calculator worked.
Other mechanical calculators followed and this is an image of "The Millionaire" calculator. This photo is from the Lowell Observatory in Flagstaff, AZ. You can see from the wear that it had heavy use and presumably it was used for astronomical calculations.
Hermann Hollerith developed a device that aided the processing of the 1890 census data. It was so successful that the initial data were available in a matter of weeks. This is in contrast to the previous census in which the results weren't available for several years. He founded a company that specialized in tabulating and organizing data and his devices helped to automate the mass of paperwork that was choking businesses in the early years of the 20th century. Hollerith's company was merged with the Computing-Tabulating-Recording Company (CTRC) in 1911 and this company eventually became IBM. Here's a view of an early Hollerith machine and more modern (c. 1960) Model 029 keypunch machine.
The first computer bug really was a bug! A moth wedged itself in between two relay contacts in the Harvard II calculator and today it is preserved in the log book at the Naval Surface Warfare Center Computer Museum at Dahlgren, Virginia. Here's an image of the bug from their web site.
The Enigma machine was a German W.W.II encryption device that was very sophisticated for this era. It was nearly impossible to break the system but the allies succeeded with luck, skill, and the very first digital computer. Sadly, this computer was destroyed at the end of the war along with most of the notes and working papers of the code breaking group. Today computers play a significant role in making and breaking military and commercial cyphers. Here's an Enigma machine on exhibit in the Smithsonian.
First generation electronic computers appeared in the 1950's and they used vacuum computers for the switching elements. They were one-of-a-kind computers and very expensive to build and operate. The air conditioning requirements were formidable because of the heat given off by the vacuum tubes. There are two views of the Univac console. This system first appeared in 1950 and it correctly predicted Eisenhower's victory in the 1952 election. CBS chose not to report the prediction until it had been verified by hand. The image on the far right is a SAGE Air Defense computer console. This system was designed to warn of air attacks on North America.
Second generation computers used transistors in place of the vacuum tubes. They were faster, smaller, more reliable, and gave off less heat. They started to appear in the 1960's. Note that the personal computer (PC) wasn't an option in this era. Computers were big, bulky, and expensive and they lived behind glass walls away from the users. Punch cards were the most common form of input.
Third generation computers used integrated circuits. While still pretty big they were still smaller, more reliable and more powerful than the previous generation. Note the disk drives on the DEC 2060. These were the size of a small washing machine and held about 450 megabytes of data. The image on the far right is a personal computer motherboard with several integrated circuits. This is the basic technology that's seen in most PCs today.
The Digital Equipment Corporation (DEC) introduced the first true personal computers in the late 1960's. These machines were personal only in that they fit on top of your desk. A major application of their first computer, the PDP-1, was a "space war" video game controlled by a light pen. Also here is the very famous DEC PDP-8 computer as it appears in a Smithsonian exhibit. The PDP-8 can be considered the first widely available personal computer even though it cost $10k-$50k. The machine at the far right is a DEC PDP-15 that was used by the FBI as an automated fingerprint identification system.
It's hard to define the precise birth date of the personal computer. Old issues of Byte Magazine from the 1970's chronicle this wild and woolly time of experimentation. It was the rule rather than the exception to build your own hardware, program it, and share the experiences with fellow hobbyists.
One of the earliest hobby kits was the Altair 8800. It was available from MITS and the kit cost $397. This machine had a 64 kB memory (max), 2 microsecond add time, an Intel 8080 processor and 8 bit bus. Front panel switches and lights were the major input/output devices. (It was possible to add a teletype interface but that was only for the folks with lots of money!) Here's an image of the January 1975 issue of Popular Electronics where the Altair was described.
In November 1975 Popular Electronics described the Altair 680, a computer that was billed as being "half the price of the Altair 8800". This price reduction foretold the current trend in personal computers!
I have no idea why I kept these issues all these years but I've been told that they command about $90 on eBay.