The Altair 8800 was developed by the American company, Micro Instrumentation and Telemetry Systems (MITS). The computer was sold as a kit (users had to assemble the machines at home) at a price of 439 US dollars, while assembled computers were also available for purchase for about one and a half times as much (621 US dollars). The company hoped to sell only a few hundred units, but the article published in Popular Electronics raised interest and boosted sales. Eventually several thousand units were sold and a new era truly commenced.
At the first glimpse, the Altair 8800 no way looks like a real computer, it much rather resembles a measurement instrument or perhaps an oversized router because of the numerous LEDs on the front panel. And you would look in vain for the usual connectors on the rear.
Removing the top cover of the box, you can have a look at the interior of the machine. Behind the front panel there is a printed circuit board where front panel switches and LEDs were fixed. At the bottom of the box, there is a motherboard with four edge connectors where expansion cards can be inserted.
There is room in the machine for a maximum of four motherboards with 16 slots altogether. The motherboard itself has no circuit components whatsoever, only slots and their interconnectors.
The computer bus designed for the Altair was named S-100, which was to become de facto standard in the world of microcomputers.
The basic configuration included expansion cards: a processor card with 2MHz Intel 8080 and a 1kB RAM card with 256-byte memory. The memory could be expanded up to 64kB (it had a 16-bit address bus).
The simplest configuration of the machine only had 256-byte RAM and lacked any kind of peripherals. Such a machine could not really be used for many things as every time it was turned on, the programme you wanted to run had to be tediously entered byte by byte in machine code using the switches, and the output of the computer was limited to the LEDs on the front panel. It was not really possible to write more serious applications than LED chaser for Knight Rider.
Nevertheless, even a game (Kill the Bit) was created for the “naked” Altair (size of the code is only 24 bytes), which you could play on the front panel of the computer.
Much more was needed to put the machine to more serious use. First of all, at least 4kB RAM (264 US dollars) was needed, but it was even better if you had 8kB RAM (that cost 528 US dollars, more than the computer itself), but this would enable you to run the more developed, 8kB version of BASIC.
In addition you would need a serial port expansion card that allowed your computer to communicate with some sort of a peripheral, which would most commonly be the teletype in the mid-1970s. The device could be best visualised as an electric typewriter with a serial port. The most popular model was the ASR-33 teletype (for 1500 US dollars) with built-in punched tape reader, which allowed the computer to load programmes. The machine printed 10 characters per second. The teletype was slow, noisy, and difficult to use, what’s more, it wasted a lot of paper, yet it was the least expensive “all in one” peripheral because it performed the functions of a keyboard, a screen, a printer, and background memory.
The Altair equipped with CRT-based terminal and floppy drive could be used for serious office work. With 16kB RAM, it could run Gary Kilddal’s legendary operating system, the CP/M, which, thanks to its easy portability, was soon to become standard for Intel 8080 or Z80 processor based computers. In the late 1970s, a number of office applications were released for the CP/M such as the dBase database manager, the WordStar word processor or the SuperCalc spreadsheet programme.
If you would like to try your hand at this computer and would like to experience what it was like to work on it or to develop it 35-40 years ago, you have three options: buy an original Altair on eBay, purchase a newly manufactured Altair replica, or use an emulator.
The “Altair BASIC” was a BASIC programming language, the very first product by Microsoft (then called Micr-Soft). Barely 4kB RAM was enough to run the first version of the programme (3.2), and after uploading, 972 byte memory was still retained for BASIC programmes. BASIC interpreters constituted Microsoft’s main products before MS-DOS was released. BASIC for the Altair was to become the basics for Commodore BASIC and GW-BASIC published for PCs.
The Altair BASIC too will turn 40 this year, which I would like to use as an opportunity to give a more detailed account how the programme was created, how it worked, and share the experiences I gained in porting it for an ENTERPRISE 128 computer.