What's a Computer Operating System?

[Cheerful Charlie]

https://en.wikipedia.org/wiki/History_of_Unix

I'd forgotten some of it , the OS wars. Thenbst aspect of freemarket comprtition.

I alawys assiciare Unuix with the DEC Vax system, it is was a common system used befor e the PC. In the 80s at Lockheed there were several VAX cluster on the campus. User had terminals in offices. To support the system departments were charged by the CPU second of run time. If you wanted fast numerical processing you had to pay extra to use a hardware math processor. Today the math coprocessor is built into the processor. On the first PCs you had to buy a hardware math accelerator chip that plugged into the motherboard.

The VAX system was not unlike the first IBM pc. It had on open archtecture and companies made plug in boards. Floating Point Systems made a math coprocessor fpr the VAX.

How many here remember Microsoft's Unix for PCs, Xenix? A variety licensed from ATT.

https://en.wikipedia.org/wiki/Xenix

"Microsoft hopes that XENIX will become the preferred choice for software production and exchange", the company stated in 1981.^[8] Microsoft referred to its own MS-DOS as its "single-user, single-tasking operating system",^[31] and advised customers that wanted multiuser or multitasking support to buy Xenix.^[31][32] It planned to over time improve MS-DOS so it would be almost indistinguishable from single-user Xenix, or XEDOS, which would also run on the 68000, Z8000, and LSI-11; they would be upwardly compatible with Xenix, which BYTE in 1983 described as "the multi-user MS-DOS of the future".

Instead, we got Windows.

 

[steve_bank]

https://en.wikipedia.org/wiki/History_of_Unix

I'd forgotten some of it , the OS wars. Thenbst aspect of freemarket comprtition.

I alawys assiciare Unuix with the DEC Vax system, it is was a common system used befor e the PC. In the 80s at Lockheed there were several VAX cluster on the campus. User had terminals in offices. To support the system departments were charged by the CPU second of run time. If you wanted fast numerical processing you had to pay extra to use a hardware math processor. Today the math coprocessor is built into the processor. On the first PCs you had to buy a hardware math accelerator chip that plugged into the motherboard.

The VAX system was not unlike the first IBM pc. It had on open archtecture and companies made plug in boards. Floating Point Systems made a math coprocessor fpr the VAX.

How many here remember Microsoft's Unix for PCs, Xenix? A variety licensed from ATT.

https://en.wikipedia.org/wiki/Xenix

"Microsoft hopes that XENIX will become the preferred choice for software production and exchange", the company stated in 1981.^[8] Microsoft referred to its own MS-DOS as its "single-user, single-tasking operating system",^[31] and advised customers that wanted multiuser or multitasking support to buy Xenix.^[31][32] It planned to over time improve MS-DOS so it would be almost indistinguishable from single-user Xenix, or XEDOS, which would also run on the 68000, Z8000, and LSI-11; they would be upwardly compatible with Xenix, which BYTE in 1983 described as "the multi-user MS-DOS of the future".

Instead, we got Windows.

In 1979 when I was service engineer for ADP in Portland I took home a PDP 11 to play with. I worked on what was called a mini computer made by a company called Microdata. The CPU was comprised of bit slice TTL logic.

There was Sun, Apollo, and Daisy who made computers for science and engineering. The class of machines was called workstations.

I worked at Intel in the 80s in Oregon. Our office computers were Intel Multibus II based running Xenix. Intel used to sell computers.

VAX stood for virtual archtecture. Users were given CPU time alotments. With limited RAM the OS swiched user code in and out of RAM.

Multi user was limited by free RAM.

Then the I286-386 came along with protected mode allowing software isolation of users. One of the big problems ubder DOS was that user code could index anywhere in memory sometimes crashing the system. Intel processors went with segmented memory to support multi user. The processor has what was called a rask and context swith. When switching user segents the current state was quickly placed on a stack.

It is starting to come back. Haven't thought of this stuff in a long time.