TZ

[Bill Wood]

In the 'flight data' world we stick with UT2 for many good
reasons, zb, the 'flight' may orbit the earth. This has been
the case forever.

For DOS, DOS-based OSs, and OS2, all my experience is that the
TOD (Time of Day) clock is set to local time if you expect any
SW (that cares) to operate properly. For example, the OS2 time
sychronization program that I've used for over 5 years sets my
TOD clock in accordance with the TZ variable.

Most computer folks don't really have a feel for true
'real-time' computer systems. I mention this because the term
'Real-Time Clock' has a different, more general meaning in that
world. It is the heart beat of the external process which the
computer must, without fail, service on time. It may be a TOD
clock, but usually its a regular or irregular series of
pulses/pulse patterns. One thing that is often required is that
the 'times' of these external events be logged. The computer's
clock is never used for this (in my experience) as it has
neither the accuracy nor the time resolution required for
serious purposes. Thus in the real real-time world, the
characteristics of the computer's clock are largely irrelevant.
In fact, until the advent of the POSIX real-time extensions,
standard UNIX (God bless it) was not suited at all to real-time
computing. Neither, of course, was DOS, etc.


w3

Bill Wood
Las Vegas, NV
wwwood@lv.rmci.net

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