From: commodorejohn@gmail.com   
      
   On Mon, 10 Mar 2025 20:20:02 -0000 (UTC)   
   cross@spitfire.i.gajendra.net (Dan Cross) wrote:   
      
   > But I do know a lot about operating systems, and the objections   
   > to categorizing things like MS-DOS as "a *real* OS" are not mere   
   > handwaving that boils down to "Because Reasons"; there are   
   > actual definitions in use across the field one can look to, and   
   > MS-DOS et al simply do not meet them.  It's great that control   
   > software in the early PC era let people do useful work with   
   > those machines; that doesn't mean that software was good or fit   
   > reasonable definitions of what an "Operating System" is.   
      
   So let's dig into that a bit. Merriam-Webster defines an "operating   
   system" thusly:   
      
   > software that controls the operation of a computer and directs the   
   > processing of programs (as by assigning storage space in memory and   
   > controlling input and output functions)   
      
   Wikipedia, being edited by Wikipedians, is a little more weird and   
   obtuse, but more or less in accord:   
      
   > Software that is designed for controlling the allocation and the use   
   > of various hardware resources to tasks and remote terminals.   
      
   MS-DOS very definitely takes control of the computer - it does not   
   *hold onto it* very tightly, but there's no particular reason it should   
   have to. In a single-tasking, single-user environment any operation the   
   user invokes can be Considered Legitimate, and this loose approach to   
   protection makes it possible for third-party or user-written software to   
   hook into interrupts/API calls and extend the system easily (although   
   DOS users generally made less use of this than classic MacOS users did.)   
      
   It also manages memory allocation (enabling applications, drivers, and   
   TSRs to co-exist safely, provided they behave themselves) and handles   
   input and output to/from screen/keyboard, disk, and parallel and serial   
   ports. Again, it does not *prevent* programs from taking control of   
   these things themselves, but that's a trade-off - yes, you lose some   
   security,* assuming you even care about that, but you gain flexibility.   
   (Supporting new hardware is generally as simple as writing a program to   
   frob the appropriate ports, unless the OS needs to be able to treat it   
   as a standard storage/communications channel. Even then, hooking into   
   the necessary interrupts is fairly straightforward.)   
      
   * (And it's worth noting that, in the original PC architecture pre-286,   
     it's functionally impossible to do protection anyway. There's not a   
     damn thing *any* OS running on an 8086 can do to prevent an errant   
     program from scribbling over the OS/another process or frobbing an   
     I/O port something else is trying to manage.)   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)