1991 Review of Coherent
Before Linux (just before Linux), there were other attempts to bring a Unix-like OS to the masses. I came across this review that I wrote in 1991.
I am writing this article using MicroEMACS under Coherent. Using EMACS may not be an intelligent choice; I am totally unfamiliar with it (I'm a vi user from way back), and am undoubtedly mere keystrokes away from losing everything. However, this knowledge does add excitement to the undertaking. Some people sky-dive; I write with unfamiliar tools. Same thing, I think.
If you have somehow missed the full page ads in Byte, and have ignored the spirited discussions on Bix and Prodigy and everywhere else, you may not be aware that Coherent is a $99.95 Unix clone. The general heightening of interest in Unix has put this product in the right place at the right time. There is a lot of Unix curiosity out there, and Coherent is a cheap way to take a test drive.
Coherent is sparing of your hard drive. You can install it in as little as 7 megabytes (more is better, of course). If I install SCO Xenix, it of course is much more expensive but also requires 40 megabytes of precious drive space.
Coherent isn't really comparable to SCO. The SCO Xenix manual set occupies more cubic inches than my computer itself; Coherent has one manual (1,000+ pages). Coherent has 4 install disks; SCO's set won't even fit in two thick plastic disk cases. Coherent costs just under $100.00; SCO Xenix (with the development system) is ten times that. SCO really does take half a day to install (I do this for a living) while Coherent really does only take a half hour to a running system. Finally, I definitely have not been recommending Coherent for business use!
I have been enthusiastically recommending Coherent to people who want a taste of what Unix is all about, as a learning tool - "Learn Unix at Home" or something like that.
Coherent is not without its detractors. I have seen some bitter diatribes detailing its limitations, its bugs, and its deviation from The True Path. I can only wonder what these sour-pusses expected for their hundred dollars. This is a complete and working operating system with a C compiler, an assembler, a debugger, support for DOS disks, support for uucp, three editors (ed, vi and emacs), complete manual pages on-line, support for multi-port serial cards and scsi drives, games, mail, ram disks and some 200 typical Unix commands. In other words, it may be a toy, but it is a finely engineered, highly crafted and lovingly detailed plaything. Foo on the nay-sayers!
One complaint I have heard stems from the fact that the C compiler only supports "small model" programs - that is, 64K of code and 64K of data. One person I talked to insisted that you can't write "real" programs with such limitations. No, I suppose you can't write the next Lotus-killer on Coherent. You could write something better than Visicalc though - the original of that ran on Z80's with less than 48K of total memory! "Real" programs, indeed!
Another constant carping concerns uucp. Coherent's version is certainly not the latest, and has a few traps for the unwary. However, that's not unusual with uucp. I don't think anyone has ever set up uucp correctly the very first time on a new system. Even I managed to get it wrong more than once, but it was just carelessness, haste and not bothering to read the manual that caused all my problems.
Coherent's /bin/sh lacks some niceties and has some bugs. You can't define a shell function. You can't include a new-line inside double quotes (though you can with single quotes). There are a few other little omissions and sins which the nit-pickers can tell you all about.
The manual has taken its share of criticism. Rather than dividing the commands into the traditional sections, Coherent has produced a "Lexicon", which just lists everything alphabetically - commands, library functions and all. Apparently the division of commands into sections was ordained by some omnipotent being; the Coherent haters certainly see this organization as blasphemous! I actually like the manual. It includes definitions of terms for people new to Unix or new to computing. For example, all of the following are explained:
address, alignment, arena, array, bit, bit map, buffer, byte, cast, daemon, executable file, field, file, FILE, file descriptor, filter, function, GMT, i-node, interrupt, lvalue, macro, manifest constant, modulus, NULL, nyblle, object format, operator, pattern, pipe, port, precedence, process, random access, ranlib, read-only memory, register variable, root, rvalue, stack, standard error, standard input, standard output, sticky bit, stream, structure, superuser.. and more.
These aren't chintzy little definitions, either. Most are at least half a page and some run two or three pages of unusually lucid explanation. I can't think of any other place where as much Unix related material is packed between two covers.
All in all, this has to be worth much more than the price charged. If you need to learn because your boss has decided to "Unix" the place, or if you are the boss and want to get a feel for the territory, this is for you. You'll get at least a hundred hours of fun (it will take you that long to try everything out) so it's pretty cheap entertainment if nothing else.
I think I still have that Coherent manual here somewhere, but I can't find it right now. It may have gotten tossed out with the old BSD 386 manuals and the early Linux CD's. I wish I could keep all this old stuff, but there's just too much of it.
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