Post by Soviet_MarioPost by William UnruhThere was once an operating sysem called DOS. It all fit onto a
little floppy disk. Dropped you into a terminal window. If you
needed anything you ran a program to do it. In fact there was no
init system.
I'm not so sure how to classify CONFIG.SYS and AUTOEXEC.BAT
In order to get most peripherals drivers work you had to
manually load these with config (prequel) or autoexec
(sequel), so imho they were sort of halfway between
configuration files and init system, as they affected the
way the DOS would start
It's a good analogy, yes. CONFIG.SYS would load device drivers and a
few TSRs, and AUTOEXEC.BAT would set up the runtime environment, which
could also include the loading of TSRs.
Post by Soviet_MarioPost by William UnruhIt was just the kernel that did it all
in DOS????? dos kernel did very very little basic work, not
even able to see the whole memory without some further
drivers such as "highmem or himem.SYS" (i cant recall the
exact spell).
HIMEM.SYS (later HIMEM.EXE) for XMS support, and EMM386.SYS (later
EMM386.EXE) for either EMS or UMB support — it could not do both at the
same time.
In addition to that, all Windows versions up until and including
Windows ME — but excluding the NT-based Windows versions — still ran all
code and data in the processor's ring 0, using DPMS (DOS Protected Mode
Specification).
Post by Soviet_MarioIt just managed to support FAT and low / middle level disk
operations. Also the CD was not supported natively by many
DOS, and had to be "inited" by another external driver
loaded in config.sys
I think what Bill means is that in DOS, *everything* ran in kernel
mode — even user applications — because the 8086/8088 processor (and
any later x86 processor when running in real mode) doesn't have
privilege separation, nor does it have access to the processor's memory
management unit.
So there were plenty of occasions where DOS didn't have a device driver
for a specific device to be used in a certain application, but whereby
the application itself came with its own device driver.
For instance, WordPerfect 5.x came with its own mouse driver, its own
printer drivers and its own graphics driver. So did Lotus 123, dBASE
III/IV, TurboPascal, Freehand, and several other applications.
DOS was therefore not a real operating system. It was essentially an
executable loader on top of the BIOS firmware, and it had some
rudimentary file management and memory management utilities.
As soon as an application was loaded into memory, DOS would take a step
back, and the application had full control over the machine until it
exited again. Then DOS had to reload its command interpreter
COMMAND.COM, either from the hard-coded default — i.e. the root
directory of the boot drive — or the path to COMMAND.COM as set via the
%COMSPEC variable, which was commonly set in AUTOEXEC.BAT.
--
With respect,
= Aragorn =