An operating system (OS) is basically a
program (usually: a set of programs) that mediates between human users
and the computer, and that can do most of the things most programs
that may run on the computer need: storing and retrieving from disks
or other media; handling user input; drawing to the screen; and more.
I have some experience with six kinds of
OS, namely in historical order CP/M, DOS, Apple, Windows, Mac, Linux.
All of these OSs had versions, often many, of which generally the
later ones were more capable than the earlier ones, and for most there
was a rather intimate relationship with a certain kind of computer
There are more OSs, and there have been
considerably more, but currently most computer users work with
Windows, Mac or Linux.
CP/M I knew from an Osborne
computer produced in 1982 or 1983. It was an early OS for what at the
time was called "home computing", and is supposed to have been rather
well-designed. I can't say much about it, except that it did its job
on the Osborne quite well.
DOS - acronymic speech for "Disk
Operating System" - was (rapidly) designed for the IBM PC and similar
computers and was marketed very successfully by a small software
company called Microsoft, that had bought it from its developer.
Both CP/M and DOS were 'character based'
in the sense that they primarily dealt with the screen as if it was
made of series of rows of places on which one could place one
character. The reason was that personal computers around, say, 1985
did not have enough processing speed and memory to do much fancy
processing with a screen made up of pixels.
Apple - I use this name, somewhat
imprecisely, for rectangular boxes with small graphical black and
white screens - I learned to use in the university in the late
eighties. They were in many ways, being graphical, more pleasant to
look at and work with than what DOS could do on a PC, but they were
also more expensive.
Windows I knew first working
under DOS, where it did produce a graphical environment like that of
Apple, except that it was much less powerful, quite slow, and prone to
crashes, for which reason I never did much with it on PCs running DOS.
Mac is the name I use for the
follow-ups of the Apple I described above. I have some experience with
this, but not much.
Linux I have tried quite a few
times over the last 8 years. For various reasons - open source, no
Microsoft - it is better than Windows, but I have had little luck with
it and for the moment and the last years it is less fit for my
purposes (and health: I
don't have the health even if I had the inclinations to puzzle out the
arcana of Linux).
I am in principle much in favour of
Linux, but from what I've seen so far from it the developers seem not
to have been able as yet to lift it beyond an OS for techies.