A college dormitory room in Ohio on a snowy March night, on a narrow wooden desk under a gooseneck lamp a flat wide computer box forty-three centimetres wide, its lid and upper sides of light grey sheet steel with ventilation slots, its lower sides and front frame light blue, the dark grey-black front panel with two rows of small red lights, a few glowing, below them a long row of silver toggle levers, along the bottom a plain brushed aluminium strip, a hand in a navy sweatshirt sleeve flipping one silver lever, an opened brown shipping carton on the floor with crumpled packing paper, an unmade bunk bed, frost on the dark window.
What it was used for
A kit for electronics hobbyists, announced on the cover of Popular Electronics in January 1975. Built by Micro Instrumentation and Telemetry Systems (MITS) of Albuquerque under H. Edward Roberts, a firm that had previously made electronics kits for model rockets, and calculators. It was operated by toggle switches on the front panel, with results read off light-emitting diodes. No screen, keyboard or storage was included. The Computer History Museum records for its example an Intel 8080, 8-bit word length and 256 bytes of primary memory, weighing 29 lb.
What was new
What stands out is the ratio of processor to price, not invention: an 8-bit microprocessor in a kit that actually shipped, for about 400 dollars, while the Micral N had been on sale since 1973. What the Altair set off was demand. On the Smithsonian's account Roberts hoped to break even at 200 units sold and had a backlog of 4,000 orders within 3 months. The basic kit held 256 bytes of memory; anyone wanting to do something with it had to buy plug-in boards. MITS was sold to Pertec in 1977 and the line ended shortly after.
What the sources leave open: Prices differ: the Smithsonian, citing the magazine, gives 395 dollars as a kit and 498 dollars assembled; the Computer History Museum catalogue gives 397 dollars. Hence "about 400 dollars" in the text. The Smithsonian dates its object to 1974, while the magazine cover appeared in January 1975. I found no full-year 1975 unit figures in any museum source.