From: smirzo@example.com   
      
   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.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)