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Controlcodesmostlyhandlecommunications b etweenyour computerand
thepnnter.atthelowestlevel,atcablelevel.Forexample,a coupleofcontrol
codesmakesurethe printerbufler(yourprinter'sstoragememory)doesn't
overflow. In this book we'll indicate control codes enclosed by angle
bracketsto their abbreviationsin the table: <FF> means the Form Feed
controlcode,whichadvancestheprinterto thenextpagejust as the PRINT
buttondoes.
Escape sequences
Control code 27, <ESC> or Escape, is a particularlyimportantone for
printers.
To
tell your printer all the things you might need— setting margins,
saying where to print, choosing a particular font, starting graphics and so
on— requires many more than just two or three dozen control codes. So the
<ESC> control code has a special meaning: <ESC> means "the next
character specifies a command, not something to be printed".
Thereforeif you sendjust the character4 to the printerit will printa 4 and
that'sall. 13utifyousendthe <ESC>codejust beforethe 4 thenthe printer
(in EX-800
mode) will switch over to italics text. Extending the control
codes this way gives you many more commands to control
yourprinter.in
fact,these"Escapesequences"makeup mostofthe StarLaserPnntcr'slan-
guage.
In this book we'll leave spacesbetweencharacterswhen we show escape
sequences.You'llfind
<ESC>
(S op
IOh 12vos 3T
a bit more readablethan
<ESC> (sOp10h12vOs3T
Butrememberthat you are not to sendthosespacesif you send commands
to the printer.
To sumup, printercommandsare of two types.A controlcode is a single-
charactercommandthat tellsyourprinterto do something, l ikemovedown
one line. An Escapesequencecontrolsa printeroperationtoo, but is more
thanonecharacterlong.Sincetheyarecommands, n eithercontrolcodesnor
escapesequencesam usuallyprintablecharacters.
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