4 ms·

Kinda like DOS apps?

• nostrademons 12y ago
  The bare-metal OS was common in a lot of early microcomputers...even the Macintosh (before System 7) had something that was more akin to an application support library than a real OS. DOS I think was a real OS; you communicated with it by invoking INT21 and putting a subfunction (syscall) number in AH, rather than jumping directly to a library function's address as I believe the Mac did. I'd be curious if it would work even better today because so many language runtimes have many common OS services in them, eg. Erlang and Go have green threads, many have garbage collection. Making the GC aware of the page table seemed to be very useful in Lisp Machines.
  • ksherlock 12y ago
    The Classic MacOS toolbox used reserved instructions ($A000--$AFFF were reserved in the 68000 instruction set) which invoked the interrupt handler. Tool calls covered everything from string comparisons to windows and graphics but also included undeniably OS level stuff like opening files and allocating memory. You could use a toolbox call to get a function's address and call it directly, but that was mostly used for patching the toolbox.