100. Printer routine snag
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If you wish to send text to the printer only, (ie with nothing appearing on
the screen), there are two simple ways of doing it. You can precede the text
with VDU2,21 , and follow it with VDU6,3 . Alternatively, you can precede it
with *FX3,10 , (or *FX3,9 in the case of RS423 printers), and follow it with
*FX3,0 , (or simply *FX3). In the latter case no VDU2 or VDU3 is necessary,
and in both cases the character set by *FX6,- is not sent to the printer.
This character is ASCII code 10, (linefeed), by default, and is usually set
to 0 with *FX6,0 if your printer doesn't do auto-linefeeds.

This is fine until you try sending a string of VDU codes, such as for the
Greek characters shown earlier. Depending on the setting of *FX6,- , either
10's or 0's will not be sent to the printer, with all sorts of unpredictable
and horrible results. Eg VDU27,10,3,4,0,0,3 would effectively be sent as
VDU27,3,4,0,0,3 or VDU27,10,3,4,3 ! Now since 0's tend to appear much more
often than 10's in VDU statements, those of you with printers doing
auto-linefeeds are less likely to have trouble, but even so, this can be a
considerable nuisance.

There is a further snag with using VDU2,21 , and that is that if a 6 should
appear in the VDU codes, then the VDU drivers are turned back on again too
early, nasty things will happen on the screen, and the whole thing will
probably seize up. The safe solution is to use VDU2 and VDU3 as normal, and
precede each byte by 1; eg VDU1,27,1,45,1,1 , even though it is rather
tedious. What would be nice would be to tell the Beeb to send all characters
to the printer, but unfortunately, *FX6,- does not allow this to be done.