a question on history of personal computer

[yogesh]

One question always comes to my mind whenever i read about the history
of PC.
why ibm had to search for another OS?
couldn't it go for the existing mainframe OS or unix which were
available at that time???
since unix is a true multiuser and multitasking OS right from the
beginning,selecting it would certainly have avoided to design for
another multitasking OS like OS/2 and the software world would be very
much different then onwards...

what was the point in hunting for a different OS then???

regds,
yogesh joshi

[Neil W Rickert]

Post by yogesh
One question always comes to my mind whenever i read about the history
of PC.
why ibm had to search for another OS?
couldn't it go for the existing mainframe OS or unix which were
available at that time???

The 8086 processor (really, 8088) did not have the capability of
running a real operating system. In particular, it did not have a
way of restricting some instructions to the system (a supervisor
state, or protected mode).

Also memory sizes at the time were too small. The first PCs came
with 64K.

[Jonathan G Campbell]

Post by yogesh
One question always comes to my mind whenever i read about the history
of PC.
why ibm had to search for another OS?
couldn't it go for the existing mainframe OS or unix which were
available at that time???
since unix is a true multiuser and multitasking OS right from the
beginning,selecting it would certainly have avoided to design for
another multitasking OS like OS/2 and the software world would be very
much different then onwards...

I understand that UNIX, as existed then, would have needed a hard disk
and ~100KB memory. The first PC had just a (single small) floppy disk,
and AFAIK, 64KB memory.

As for mainframe OSs, I have no idea of the impact of the limitations
of the 8086 hardware with respect to mainframes of that time.

The PC was developed on a fairly tight schedule and it wouldn't have
been the first time that software was considered as an afterthought.
Also, I think there was an impression that the eventual OS should be
CP/M compatible; Digital Research were developing a 16-bit CP/M, but
it was late.

Google should be able to fill in the details.

Best regards,

Jon C.