Recreating the lost SDK for a 42-year-old operating system: VisiCorp Visi On

My partner Elaine Gord was on VisiOn's C compiler team in 1982-1984 with two others. They experimented with having two instruction sets: the native 8088 code for best performance, and a C virtual machine bytecode for code density. The two modes were mixed at the function level, and shared the same call/return stack mechanism. This was terrible for speed, but was thought necessary because the target machines did not have enough ram for the total VisiOn functionality. I don't know if the bytecode scheme got into "production".

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pdw 8 hours ago | parent [-]

All of Microsoft's applications used to do that! The 16-bit versions of Word, Excel, PowerPoint, etc all were implemented using bytecode. That technology was only integrated in Microsoft C and made public in 1992 [1], before that the Microsoft applications group used their own private C toolchain. A copy of it can be found in the Word 1.1 source release [2] ("csl").

[1] https://sandsprite.com/vb-reversing/files/Microsoft%20P-Code... [2] https://github.com/danielcosta/MSWORD

	▲	classichasclass 3 hours ago \| parent \| next [-]
		I think Multiplan for 8-bit systems was implemented in a similar fashion, which enabled it to be widely ported.
	▲	reactordev 6 hours ago \| parent \| prev [-]
		C was very much the Javascript of its day. Hand rolling toolchains and compilers to the bytecode they knew and loved (or despised). This is awesome history. Formal history only remembers the what’s, the when’s, rarely does it catalog the why’s, or how’s. The decision making process of those early programmers helped shape a whole industry.

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jdougan 3 days ago | parent | prev | next [-]

Wow, just what I wanted for Christmas. Back in the day I found VisiOn's approach fascinating since almost everything at the time was either more tightly integrated or completely unintegrated.

Maybe someone could do the the old Reason software bus based system next? As detailed in Jan 1984 Byte magazine. Lord only knows if there are surviving copies anywhere in the world.

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cramcgrab 4 hours ago | parent | prev | next [-]

Yep Mitch Kapor and the eff.

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msla 14 hours ago | parent | prev [-]

It's interesting how this article deconstructs the buzzwords used in the marketing material to get from "VisiOn is a multitasking object-oriented OS using a VM to be portable" to "VisiOn is a DOS shell that uses C structs in a documented API and was never meaningfully portable"

Seriously, the "VM" thing is stupid:

> The term "virtual machine" used by VisiOn developers means something different from what we mean by the words "virtual machine" today. The closest word we use today would be "API". That's right, Visi On applications use a cross-platform API. Just like almost any other operating system today. I bet it was a really cool idea back in 1983, though.

As if VM isn't overloaded enough already (quick: does it mean "Virtual Memory", "Virtual Machine" as in the JVM, or "Virtual Machine" as in Xen?) using it to mean "API" is just dishonest.

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retrac 12 hours ago | parent | next [-]

Processes on modern operating systems are a type of virtual machine. On Linux or Windows, processes are provided with the illusion of infinite memory. And there is the illusion of infinite parallel threads of execution, bounded only by storage. That is a kind of virtualization, just not full machine virtualization.

At the machine level the boundary between machine instructions and system calls and API becomes blurry. If you don't have a floating point unit, the instructions trap and a routine in the kernel can perform the same thing. Instruction sets are APIs. Many operating systems present their system calls as if they were special machine instructions.

This kind of phrasing is less common today, where "virtual machine" is usually equivalent to "full machine virtualization", but you'll encounter this broader sense in earlier literature.

	▲	bananaflag 11 hours ago \| parent [-]
		Also in this OS textbook https://pages.cs.wisc.edu/~remzi/OSTEP/

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jdougan 13 hours ago | parent | prev [-]

The latter 2 usages are pretty much the same. They just have different virtual instruction sets.