The home computer is 40 years old. The one that appeared in January 1975 issue of Popular Electronics. Used copies of this issue typically fetch about a hundred dollars on eBay, but fortunately, a full scan of the issue is available at AmericanRadioHistory.com.  The January issue carried a summary of the computer and some of the construction details. The February issue included an introduction to programming it.

The January issue carried an editorial announcing that the home computer was here. It correctly noted, “for many years, we’ve been reading and hearing about how computers will one day be a household item. Therefore, we’re especially proud to present in this issue the first commercial type of minicomputer project ever published that’s priced within reach of many households–the Altair 8800, with an under-$400 complete kit cost, including cabinet.”

The construction article billed the computer as the “Popular Electronics/MITS Altair 8800.” It was built around an Intel 8080 CPU chip, which could handle up to 78 instructions. The construction article did contain a parts list, but not full PC board templates. Those were available by mail, but it’s likely that most builders took advantage of the computer’s being available in kit form for $397, or fully assembled for $398 from MITS, Inc.

The basic computer came with 256 words of memory, with up to 65,000 being available through add-ons. The parts list called for a 2 MHz crystal, indicating the processor’s speed.

The January article suggested some possible applications for the computer, such as use as a programmable scientific calculator, machine controller, or automatic drafting machine. The February issue included the basics of programming the computer, along with a sample program to add the contents of two of the registers and store them in a third.

Programming was accomplished from the spring-loaded switches on the front panel. Another possibility for programming the computer was to use a computer terminal, and the article suggests the design that had appeared in the December 1974 issue, shown here. It’s probably not the mental image that would come to mind upon hearing the phrase “computer terminal.” It’s simply a method of sending an octal code to the computer, and receiving one back.

It was a year or two after the computer first appeared that I first saw one. When I saw it, the builder hadn’t really come up with anything for it to do. He was working on interfacing it with a teletype machine, and at that point, all he could make it do was have it output the character associated with a particular ASCII code. In other words, he entered a number using the front panel switches, and it printed out the corresponding letter. I remember not being too impressed, but I guess I did realize that at some point, I might have a computer in my house.

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