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On Sun, 16 Nov 2003 20:38:36 +0100 (CET)
"Carlos E. R."
The Sunday 2003-11-16 at 10:43 -0500, Jerry Feldman wrote:
fact, the first PCs had about 64 Kbytes. There is no much place there for big disk buffers, nor probably for the extra coding needed :-)
While this is true, Unix likewise was developed on very small machines, but it was developed in a disk environment where MS-DOS was developed primarily in a floppy environment.
Unix was developed from Multics as a time sharing system where MS-DOS was developed as a single user environment. The real difference is in how Unix (and Linux) handle files. Even back in the 16 bit PDP11 days, Unix did have the buffering. While DOS did have buffering, as you mention, it was very limited.
If I'm not mistaken, those machines had litle RAM, but had some kind of memory swap to disk, or virtual memory systems. It was a more complete and complex design. The IBM PC was a "Personal" computer, much simpler. It could even work with no OS, with ROM basic, and an audio tape machine as storage!
Also, dos/bios was not reentrant, meaning that there was no way to request saving two files simultaneously. Head movement planning had no interest, chunks were saved to disk inmediately, with the error result code given back to the caller right away (wich makes sense for a floppy).
I think that agrees with what you say :-)
Yes. The main difference:
Unix/Linux from day 1 was multi-user/multi-tasking.
DOS (from day 1 to 6.c) was single-user/single tasking. The appearance
of DOS multi-tasking was via Terminate and Stay resident (TSR). DOS 7
was the first multi-tasking Microsoft DOS, but it was never officially
released in the US, but was part of Windows95.
- --
Jerry Feldman