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GAZETTE
JULY/AUGUST 1990
and Networking
explained
UNIX
1989 was the 20th anniversary of UN I X . Why is it that it is only
now gaining acceptability and becoming such a buzz word? The
main reason is that when US legislation released Bell Laboratories,
the research wi ng of AT&T, from restrictions imposed because of
their monopoly position with telephones and allowed them to
license it commercially to other companies they went about
marketing it widely, spending huge amounts of money. There was
no great secret about what Unix did and how it operated as it was
in free use in most of the Amer i can Universities for years. It was
a very shrewd move by Bell Labs to license it for a nominal fee to
the Amer i can Universities as when it was eventually launched on
the market there were thousands of graduates who had used it.
In the period leading up to the
release of UNIX, most computer
manufacturers were developing
their own versions under licence for
their own equipment. At the same
time Intel were lauching their
8 0 2 86 and 8 0 3 86 micropro-
cessors on the market and they
wanted an operating system to
work on these. Software houses
were quick to see the opportunity
to develop an operating system for
the new cheaper hardware. Micro-
soft was one of the first to do this
with its version called Xenix. SCO
(Santa Cruz Operation) was
another company which brought
Microsoft's Xenix a stage further
and called it SCO Xenix (Microsoft
have a large share in SCO). At this
stage most computer manufact-
urers have their own version of
UNIX. This means the " n ew
standard operating system" has
many different flavours so it is not
really a standard at all. IBM has Aix,
"At this stage most computer
manufacturers have their own
version of UN I X . "
Digital has Ultrix, SCO has Xenix,
Wang has Inix. My own product
TOPS legal will run on both MS-
DOS and Xenix, but will not run on
some of the other versions of Unix.
The problem with Unix is that the
standard is at a lower level and
really interesting features have
been added to the standard
operating system by the manu-
f ac t u r e r s. This is how t he
manufacturers gain their competi-
tive edge. So when a software
company makes use of one of
these features, for example win-
dows, in say an accounts program,
then the accounts program will
only run on that manufacturer's
By
Do n a l O ' L o c h l a i n n*
computer. So much for standards.
However, life would be very boring
if all computers were the same.
Prior to the release of Unix, other
software houses were developing
other operating systems to take
advantage of the 8086 and then for
the later 8 0 2 86 and 8 0 3 86
microprocessors. The main con-
tender here was of course IBM in
association with Microsoft with
MS-DOS (Microsoft - Disk Op-
erating System). This operating
system was very quick to establish
itself as the standard. Any com-
puter manufacturers who develop-
ed computers or operating systems
which did not conform to the
" I B M " s t anda rd perished or
changed course. Wang is a notable
case here. Even though, in my view,
Wang made a far superior com-
puter, it was forced in the end to
adopt the " I BM Compatibility" tag.
The main reason t hat this
happened was because of the
incredibly huge amount of software
being developed for the IBM
standard. These packages included
word processing, spreadsheet,
project management, ideas pro-
cessors, databases, communica-
tions, desktop publishing, . . . the
list is endless. Wang users were
deprived of all these packages
except in a relatively small number
of cases. On the hardware side
also, manufacturers were making
pieces of equipment that did weird
and wonderful things like read
books directly into the computer,
talk, make telephone calls, control
machines . . . etc. Here also these
were not available to unfortunates,
myself included, who did not buy
the standard.
So today where do we stand at
the microprocessor end of the
computer market? Should we go
for UNIX or should we go for MS-
DOS? Before I answer that question
let us look at how the t wo
operating systems differ.
UNIX is a multi-tasking system.
Most people will tell you that this
means t hat several tasks or
programs run at the same time.
However, this is not the complete
truth. What happens is that UNIX
allows several programs to be in
memory at the same time, but they
do not all run at the same time.
What UNIX does is " v i s i t" on each
program in memory and perform a
few instructions before visiting on
the next program and perform its
next f ew instructions. If the
number of programs is small and if
the computer is fast enough, the
user will not notice any delay as his
turn comes around so often he
thinks he has the whole computer
to himself. So on a UNIX computer
you could have a person using word
processing, another person using
accounts and someone else using
database all at the same time. All
programs are in memory at the
same time and the computer cycles
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