May June 1980 - Commodore Computers

MAY/JUNE. I 1980. ISSUE 4. COMPUTE. 111 Ill
CHEEP PRINT Hard Copy For Soft
CHEEP PRINT SOFTWARE
Cheep Print for PET is written mostly in
BASIC; a little bit of machine code is used to
BASIC; a little bit of machine code is used to
insure accuracy in timing the output signals. I have
chosen to put the machine code in the second cassette
buffer, but the code is completely relocatable and may,
for instance, be placed in high memory if you change
the top-of-memory pointer and command CLR before
trying to run the program (neglecting CLR causes
trying to run the program (neglecting CLR causes
strings to overwrite the machine code; you can guess
how I found thiss out.)
The BASIC part of Cheep Print is designed to
live at the beginning of some other program, which
I[ will refer to as the host program, and serves both
to list the host program while it is under development
and as data output software after the program has been
completed. The host program is assumed to have
line numbers of 100 and up. I have tried to structure
Cheep Print so that it contains subroutines that can be
called by the host program. . If you look over the
listing of Cheep Print, which was produced by Cheep
Print itself-- the comments were added afterwards
for documentation -- you will see that most of the
program is taken up with formatting the output for
the printer, and with the details of listing a program.
To use Cheep Print, start by making a master
copy of the program that contains all the options that
you might ever need; this copy should be saved for
future use. Then make a sub-master that has the
various parameters and options for the printer that
you will be using most. You can simply load the
master and delete those options that aren't needed,
incidentally gaining more space for the host program.
You will probably want to use Cheep Print to list
itself a few times, just to make sure that the formatting
is satisfactory, and to gain familiarity with
the sequence of operations required. When you are
about to start developing a new program, enter the
sub-master copy of Cheep Print and then key in the
host program. As you save your host program,
Cheep Print will come along with it. Line 1 of
Cheep print is a GOTO to the entry point of your
host program, so that a simple RUN command will
execute the host program. If you want a listing of
any part of the program, m , simply command RUN 10;
you will be prompted to check that your cassette
recorder is properly set up -- — cables connected and
running in record mode -- ~ and then you will be
asked which lines you want listed. The options are
the same as for the screen listing on PET: hit
RETURNRN only, and gett everything; enter A-B B (a
hyphen must be used as a separator here) and you get
lines A through B inclusive; A- gives everything from
Cost Cos!
C A McCorlhy
McCarthy
1359 W Idaho Ave
SI St Poul. Paul. MN 55108
A onwards, B- gives everything up through B; and A
alone, with no hyphen, lists the single line A. As the
program listing proceeds, the line that is currently
being processed for the Cheep Print output is listed
at the top of the screen. When the message "BREAK
IN 80" appears, the listing is done and you can turn
off the recorder.
One of the Cheep Print listing options is to put
One of the Cheep Print listing options is to put
each statement on its own private print line, thus
leaving much welcome space for comments. I have
used this style for the listing of Cheep Print; I hope
that the comments on this listing suffice to explain
what is going on, , and how to structure the various
options for your specific needs. There is, however,
one point that must be emphasized. The LIST instruction
of line 2 needs to have precisely five characters as
argument. The first time that you enter Cheep Print
from the keyboard, key in something like 2 LIST­
LIST-
LINES or 2 LIST12345. This is important because
eventually line numbers are going to be POKED here
by the commands of line 19; we need to leave
enough room for the longest possible line numbers of
five digits.
The other principal subroutines of Cheep Print,
which the host program may find useful, are:
which the host program may find useful, are:
3-4 contains identification information such as the
name of the program, date, revision, etc.; I have
found this useful also when SAVEing or VERIFYing
a program with PET's internal cassette recorder. The
command LIST 3 puts this data on the screen, then
I type the word ""SAVE" and two spaces over the line
number and S$-; hit RETURN, and the program gets
saved with a title, without the fuss of entering
the title by hand.
7 outputs the string PS, P$, and 8 outputs the single
character which has ASCII code P.
39 effects a carriage return and linefeed, and
updates the variables PX and PY which give the
current print position at the printer.
40-41 checks whether it's time for the printer to
go to the next page, and if so, it executes 42-44.
42 linefeeds to the end of the current page,
43 is an option, useful for continuous roll paper;
if the initial "RETURN" is deleted, a line of hyphens
if the initial "RETURN" is deleted, a line of hyphens
is printed at regular intervals, so your paper can be
cut neatly into single sheets of uniform size. With
fan-fold paper, line 43 may be ignored.
44 linefeeds to the top margin of where you
want to start printing on the paper.
45-49 format the string S$ for output: space from
the left edge of the paper to the left margin, print SS S$
if it fits on the current line; if it doesn't fit, output as
much as does fit, , aand then repeat the process with
the portion of SS S$ that's left over.
70 is a general purpose start-up routine. It calls
70 is a general purpose start-up routine. It calls