Software Notes; More Software Notes - Epson FX-80 User Manual

Software Notes
Astute observers will notice the trailing semicolon after the B$ in
line 40. If this line were text rather than graphics data, the Master
Reset Code in line 80 would be placed in the same text buffer and
consequently would wipe the text out. This doesn't happen with the
graphics command and data because they are gone by the time the
Master Reset Code makes its appearance. The (ESC)" K" command
has cleared the buffer.
To see this in action, add a line to your program:
5fi' INPUT A
The INPUT causes the program run to pause so that you can see that
the graphics design is printed before the program reaches the Master
Reset Code in line 80. To let the program finish, press (ENTER).
There's an important correlation to note. Anything that was in the
buffer prior to the graphics string remains unscathed, and anything
left behind is erased. To verify this, make these changes in your pro-
gram:
35 LPRINT "PROTECTED TEXT";
5fi' LPRINT "THIS WILL NOT PRINT";
and RUN it once.
In general, you need to remember that the Master Reset Code poses
no threat to graphics data. But also remember to be careful about
using trailing semicolons after text when the Master Reset Code is
lurking in the shadows.
Before continuing, delete lines 35 and 50.
More Software Notes
Sending codes from BASIC can be a problem in printing graphics
just as it is with printing text. The problem again is that the computer
handles some of the control codes-the codes between 0 and 31-in a
special way instead of delivering them to the printer as requested.
For example, one computer tries to handle form feeds by itself. It
counts lines to keep track of the Top Of Form. If a CHR$(12) is sent,
the computer intercepts it and sends instead a series of line feeds
(CHR$(10)). You can see how this would upset the printing of graph-
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