What is the Altair Original OS?

General discussions related to the Altair 8800 Clone

What is the Altair Original OS?

Postby kwiebe » February 11th, 2019, 7:35 pm

Having a slight conceptual problem understanding original Altair operation/nomenclature. I know about Altair DOS and also CP/M for Altair but I don't see any mention of those until 1977. Did the 1975-77 Altair have something akin to an OS that was identifiable/named? Or were such functions part of the original BASIC?

I might not be thinking about this right but usually there is a distinction between OS and language (i.e., programming environment) software. But the only references to software pre-1977 seem to be to BASIC.

What was Altair's OS equivalent?
-Ken
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Re: What is the Altair Original OS?

Postby TomXP411 » February 13th, 2019, 12:41 pm

The original Altair 8800 did not have an operating system. It was operated entirely through the front panel switches. The switches literally deposit values directly in memory via the S-100 bus. When loading a program from paper tape, a user had to hand-enter the 20 or so machine instructions required to boot the application - every time.

The first "operating system" (and I use this term loosely) for the Altair would have been a machine monitor, which had only 3 commands: Read, Write, and Execute memory. After that, we of course have CP/M, which was the first true operating system for the Altair, IMSAI, and other 8080 based computers.

While I thought the Turnkey monitor was built earlier, it appears to be part of the third 8800 model, which does not have all the front panel switches - just a power switch (a literal key lock, hence the name), a Start/Stop, and a Run switch. The Turnkey was configured to boot directly from a floppy disk, using a bootstrap ROM.

There were also some variations of BASIC that ran from ROM, from paper tape, from cassette, and from disk. BASIC could probably be considered the first OS for the Altair, as it predates CP/M and certainly provides OS-like functions. I believe 4K BASIC hit the market on July 1 of 1975, six months after the announcement of the Altair in Popular Electronics.
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Re: What is the Altair Original OS?

Postby kwiebe » February 13th, 2019, 7:48 pm

Thanks TomXP411, that was a great explanation!
-Ken
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Re: What is the Altair Original OS?

Postby toml_12953 » February 14th, 2019, 10:56 am

TomXP411 wrote:The original Altair 8800 did not have an operating system. It was operated entirely through the front panel switches. The switches literally deposit values directly in memory via the S-100 bus. When loading a program from paper tape, a user had to hand-enter the 20 or so machine instructions required to boot the application - every time.

The first "operating system" (and I use this term loosely) for the Altair would have been a machine monitor, which had only 3 commands: Read, Write, and Execute memory. After that, we of course have CP/M, which was the first true operating system for the Altair, IMSAI, and other 8080 based computers.

While I thought the Turnkey monitor was built earlier, it appears to be part of the third 8800 model, which does not have all the front panel switches - just a power switch (a literal key lock, hence the name), a Start/Stop, and a Run switch. The Turnkey was configured to boot directly from a floppy disk, using a bootstrap ROM.

There were also some variations of BASIC that ran from ROM, from paper tape, from cassette, and from disk. BASIC could probably be considered the first OS for the Altair, as it predates CP/M and certainly provides OS-like functions. I believe 4K BASIC hit the market on July 1 of 1975, six months after the announcement of the Altair in Popular Electronics.


The first official OS (Directly from MITS) was Altair DOS which was supposed to be an answer to the growing popularity of CP/M. It wasn't any threat to CP/M at all.
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