release dates of early microcomputer operating systems, incl. Intel ISIS

Eric Smith spacewar at
Fri Sep 18 00:03:00 CDT 2015

I wrote:
> On Twitter, @hotelzululima suggested Motorola MIKBUG, introduced in
> 1974, but IMO it's a monitor, not an operating system.

On Thu, Sep 17, 2015 at 5:17 PM, Rich Alderson
<RichA at> wrote:
> So the PDP-6 monitor, which booted from DECtape but had no other dependency
> on that medium, was not an operating system?  It provided multiple timeshared
> jobs, so was not a single-program system.

I never said such a thing.  MIKBUG is only a monitor in the sense that
all it provides it the ability to examine and deposit memory, load and
dump memory in an object format (S-records), and character I/O only to
a console device. It doesn't even have any program debugging features
to speak of. It doesn't have any form of job control. It doesn't have
any device abstraction or framework for device-independent I/O. If
that's an operating system, it's one of the crudest ones ever, being
less functional even than IBSYS/IBJOB. However, it was a perfectly
fine monitor.

Despite the PDP-6 Monitor being called "Monitor", it was obviously a
complete, full-featured operating system.

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