From: cross@spitfire.i.gajendra.net   
      
   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)   
      
   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.   
      
   	- Dan C.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)