CP/M/CPM_CDROM.iso/simtel/sigm/vols000/vol080/console.doc

Text File | 1984-04-29 | 4KB | 70 lines

      CONSOLE-CONTROL PROCEDURES FOR PASCAL/Z

    The console-control procedures "Conact", GotoXY",
and "ReadXY" are provided as built-in extensions to the
language in Pascal/M and UCSD Pascal, but not in Pascal/Z.
The accompanying files "CONACT.PSP" and "GOTOXY.PSP"
(filetype "PSP" is for "PaScal Procedure", to distinguish
such a file from an executable Pascal program) provide two
of these procedures. The third, "ReadXY", has not yet been
successfully implemented, for reasons described later.
    Since the Pascal/M and UCSD console procedures are
called frequently from programs written in either of these
two implementations of Pascal, conversion of such programs
to Pascal/Z can be done much more easily if the necessary
procedures can simply be included in the program and called
in the same way. Since most CRT terminals use different
control codes for the actions needed, however, it will be
necessary to change the codes shown here to whatever your
own terminal requires. In most cases, this will require no
changes in the procedure headings or the formal parameter
types, though, so the interface to the programs can be the
same, no matter which terminal you have. To repeat a theme
I've used elsewhere, maximum compatibility between
different programmers, and different dialects of Pascal,
should benefit all of us -- and if you take the trouble to
get these procedures working right for your hardware setup,
and then use them in your own programs, it should be one
more step toward this goal.
    Since it may not always be obvious, from the
information given in the various manuals (it certainly
wasn't in mine), exactly how to get hardware-dependent
procedures like these working right, some trial and error
may be required. To facilitate this process, I also wrote
a program called "CONSOLE.PAS", to test the procedures.
Unfortunately, neither this nor "READXY" could be included
on this disk, due to two problems with Pascal/Z that I
haven't yet figured out solutions for. One is that the
"Read" function is improperly implemented from the "Input"
(console) file, and it acts like "Readln" instead (waits
for a "Return" before accepting the input). The other is
the failure to provide a non-echoing mode for inputs from
the console, like the "Keyboard" file in Pascal/M and UCSD.
Together these flaws make it impossible to move the cursor
around under user control, or accept the X,Y return values
from "ReadXY", since everything keeps getting echoed to the
screen. I've tried a number of ways of working around these
problems, including the "Input" procedure on p. 77 of the
Pascal/Z Manual, but so far without success. If I were a
better assembly-language programmer, I might have been able
to make it work, but (now, here comes the soapbox) the
whole point of using a high-level (and in the case of
Pascal/Z, high-priced!) language is to avoid having to do
this sort of low-level hacking. After about a week of
unsuccessful attempts, I decided that there were better
ways to spend my time than trying to add features to the
language that should have been there in the first place.
Good console-control procedures are a must for a language
that's going to be used to develop serious applications
software, and I can only hope that they are provided for
Pascal/Z before much longer (sorry about the tirade, but it
was a long, frustrating experience). Anyway, try out the
two procedures that I was able to use (they seem to work in
my programs, at least -- see "ARTIL/Z.PAS" for some
examples), and good luck with them.

            Jim Bearden
            Cancer Center, University of Hawaii
            1236 Lauhala Street
            Honolulu, Hawaii 96813