Path: csiph.com!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: Salvador Mirzo Newsgroups: alt.os.development Subject: Re: z/PDOS-generic Date: Mon, 10 Mar 2025 09:21:38 -0300 Organization: A noiseless patient Spider Lines: 50 Message-ID: <87ikoh13fx.fsf@example.com> References: <9lwmO.48820$ySE.16060@fx11.iad> <87o6ybbeqw.fsf@example.com> MIME-Version: 1.0 Content-Type: text/plain Injection-Date: Mon, 10 Mar 2025 13:21:39 +0100 (CET) Injection-Info: dont-email.me; posting-host="284b53354082a8681c403d325df2439b"; logging-data="1405261"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18IuicqnhsvtXq3M5mnqLmz89O4+OgkFZg=" Cancel-Lock: sha1:1N3DVnuMDkxQ8u9C8tCGpB2bd3g= sha1:xdF9vHjbom4J10ot1D/mUiQ1TVY= Xref: csiph.com alt.os.development:18758 cross@spitfire.i.gajendra.net (Dan Cross) writes: > In article <87o6ybbeqw.fsf@example.com>, > Salvador Mirzo wrote: >>scott@slp53.sl.home (Scott Lurndal) writes: >> >>> "Paul Edwards" writes: >>>>Sure - but why not make it available anyway? >>> >>> MS-DOS is, was, and always will be a toy. It's not even >>> a real operating system. >> >>And why is that? Is it mainly because it doesn't time-share the CPU? > > It depends on your definition of an operating system, I suppose. > I like the definition Mothy Roscoe (ETH) used in his OSDI'21 > keynote: > > The operating system is that body of software that: > 1. Multiplexes the machine's hardware resources > 2. Abstracts the hardware platform > 3. Protects software princples from each other > (using the hardare) Thanks for the definition and the reference. > It's hard to see how MS-DOS fits that definition in a meaningful > way. Does it multiplex the machine's hardware resources? Well, > no; not really. While it does provide a primitive filesystem, > and exposes some interface for memory management, it only lets > one program run at a time, and that program doesn't have to use > or honor DOS's filesystem or memory management stuff. Further, > the system interface is inexorably tied to the hardware; it's > defined in terms of synchronous software traps and specific > register values. System calls are numbered, not named. > Finally, the last one is really the nail in the coffin: MS-DOS > makes absolutely no effort to protect the software principles > from each other, or even themselves; a user program can take > over and just never cede control back to DOS. > > So it's hard to see how DOS really qualifies as an OS, despite > the OS-like abstractions it provides. Thanks for the explanation. I now think that DOS is useful today in illustrating the definition (in a negative way) as you just did. I actually plan to understand more about DOS just to be able to personally give an answer like that. It also seems very useful precisely to expose a programmer to the entire machine.