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^1          U S I N G   P R I N T E R S   W I T H   A M O S .

^2                           by Jeff Tullin.

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^4 The great thing about standards, as someone once said, is that there
^4are  so  many  of them.  Nowhere is that more true, it seems, than in
^4the  world of printers, and their control codes.  Printers and Amigas
^4have  always  been  uneasy  bedpartners, and due to one or two little
^4quirks,  even  more  so  when  using  AMOS.  I've been doing a bit of
^4investigating  into  the  use of the printer from AMOS, and I came up
^4with one or two surprises!  

^6But first, a little history..

^1 Way back  in the early days of home computing, wordprocessors tended
^1to  concentrate upon the bare job of getting letters out on the page.
^1The  fancy  effects  like  underlining,  bold, italics and so on were
^1either  ignored,  assumed  to be EPSON compatible (and hard cheese if
^1your  printer  was  not), or handled by some obscure system of escape
^1code  sequence  inserting  functions.   (An escape code sequence is a
^1sequence of numbers which, when sent to the printer, tell the printer
^1to  do  something.)  The  advantage  of  this  last  system was that,
^1provided  you had a good manual for the printer, and could follow the
^1instructions,  every  feature  of  your printer was open for use from
^1within  your WP.  The problem was that it tended to get in the way of
^1your  work,  and  you  really  did  have  to know your way around the
^1printer  manual. 

^4 People  are  inherently  lazy,  however,  and  started to expect the
^4wordprocessor  to  include  built in commands to handle these special
^4printer   effects.    To  do  this,  and  be  worth  it's  salt,  the
^4wordprocessor  had  to be able to send the correct codes to a variety
^4of  printers.   For  example,  the  escape  code  sequence  to  begin
^4underlining  is quite different on IBM compatible printers to that on
^4Epson  compatible.  (which are by far the most common in use with the
^4Amiga).

^6 Thus,  the  printer  driver  was  born.   The  wordprocessor  sent a
^6'standard'  escape  code  sequence to its printer driver, the printer
^6driver  thought  to itself - 'Ah ha!  Escape A!  That means they want
^6to use double height letters.  Now, I'm an IBM driver, so when I hear
^6(Escape  A),  what  I send to the printer is actually 27, followed by
^632,  then...'  and  so  on.   Each  wordprocessor had its own printer
^6drivers,  and  they  were  legion.   Every other program with printer
^6output  would  also  use its own, and there was little common ground.
^6Most Atari ST wordprocessors still work in this fashion.

^1 The  designers  of  many  multitasking  operating systems, the Amiga
^1among them, decided that it would be a good idea if all your programs
^1could have access to a common pool of resources, like printer drivers
^1and  fonts,  and  so  establish  some  standard method of output, and
^1reduce  the memory overheads inplied by having a different driver for
^1every  application.   So,  the  Amiga  printer  driver  standard  was
^1created,  adapted  from  the  ANSI  standard  from  America, and most
^1programs will use this medium to communicate with your printer.

^4 You  use Preferences to choose the printer driver which most closely
^4resembles  your  own  printer,  and for most purposes, this will work
^4with little trouble for 'normal' text.  (Graphics, on the other hand,
^4are  a  whole  new  can  of  worms,  and are beyond the scope of this
^4article.)  The  printer  and  device  drivers are an integral part of
^4using  Amigados, and most books on the subject will cover them in far
^4too much detail for the average Amiga user.

^6 AMOS isolates  you  from  the nitty gritty of the Amigados operating
^6system,  (Look!   -  I  got  round  to  AMOS eventually!  ), but as a
^6consequence, you do not often come across the information you need to
^6access  this  sort  of  feature.  Without at least a list of the ANSI
^6codes,  you  may  will  find it tricky to get the results you want on
^6paper from within an AMOS program.

^1 Here is  where  I  hit upon the fist surprise.  AMOS does NOT Lprint
^1through  the  printer  drivers!   Instead, provided I understand this
^1correctly,  it  opens  a  port  to the Parallel device, sends data to
^1that,  AND  NEVER  CLOSES  THE  PORT!   Now  this causes all sorts of
^1problems  if you want to do anything fancy with the printer, and I'll
^1try to explain why.

^4  There are  three  main  ways  to  send data from your program to the
^4printer  port.   The  first  (the normal) way is to use AMOS's LPRINT
^4command, Eg.  LPRINT "Hello"

^6 You can  achieve  the  same  effect by opening a channel to the PAR:
^6device,  directly accessing the parallel port, Eg.

^1  OPEN OUT 1,"PAR:" : PRINT #1, data

^4The third is similar, but opens a port to the PRINTER DRIVER, by:

^1  OPEN OUT 1,"PRT:" :  PRINT #1, data

^4 (Note:   I ignore the serial port for this article - once the serial
^4port  is  configured  correctly  for  speed and parity etc., then all
^4references to PAR:  could equally apply to SER:)

^6 We'll  look at LPRINT first, the 'legal' way to talk to the printer.
^6The  only way to set printer effects via LPRINT is to look them up in
^6your  printer  manual,  lets use DOUBLESTRIKE as an example.  For the
^6LC10  printer,  and many others, the correct sequence of codes is ESC
^6G.  You can send this by LPRINT CHR$(27),"G"; This works fine, but it
^6ties  you  to writing your program for only one type of printer.  One
^6further  restriction, due to a bug in AMOS, is that you can not (yet)
^6send  CHR$(0)  to the printer through LPRINT.  This effectively rules
^6out several types of printer command.

^1Far  better  to  make  use  of the PRINTER DRIVER to achieve the most
^1common effects like italics and underline.

^4 You  are restricted in the number of things which you can ask of the
^4printer,  by  the  number  of  commands  which  the  printer  drivers
^4understand.   (About  80,  but  many of these are obscure things that
^4most  people  would never dream existed.) As printers become more and
^4more  advanced, and their features increase, so the complexity of the
^4escape  code sequences they understand increases, and the differences
^4between different manufacturers becomes more pronounced. 

^6 The  printer  drivers  'cherry pick' the most common printer effects
^6and  cater  for  them alone.  If your printer supports variable width
^6triple  height  lettering  and you want to send something to set that
^6effect  -  forget  it.   You  just  can't  do it, because there is no
^6standard  printer driver call for that effect.  So, just what can you
^6ask  the printer to do?  The Amiga Introduction Manual that came with
^6your  machine  sets  out a list of the available ANSI style commands.
^6It is on page D-2 of my manual (1.2), and to save you looking for the
^6moment,  here are some examples.  (Note:  ESC is the same as CHR$(27)
^6in AMOS Basic)

^2 So  as  not  to  confuse the magazine's driver program, all the left
^2square  brackets used in the control codes have been replaced with *.
^2Please take this into account when reading the rest of this article!


^7  SEQUENCE            FEATURE

^5  ESC c               Reset printer

^5  ESC E               Line feed & carriage return.

^5  ESC *3m             Turn on italics.

^5  ESC *23m            Turn off italics.

^5  ESC *4m             Underline on.

^5  ESC *24m            Underline off.

^5  ESC *1m             Boldface on.

^5  ESC *22m            Boldface off

^7  .... and several more.

^1 To use  these  and  the others from within AMOS, you could issue the
^1commands:

^4     OPEN OUT 1,"PRT:"
^4     PRINT #1,CHR$(27)+"*1m"      ;(which sets BOLD print.),
^4     CLOSE 1

^1replacing  the "*1m" with the correct string for the effect you want.

^2See PS at end of article!

^6 The printer  driver  will change this string into the right ones for
^6your  printer, and all is well.  (You can open and close this port as
^6many  times  as  you wish during the program, but if you have already
^6used LPRINT anywhere in your program, this will produce an I/O error,
^6as the PAR:  port is left open by the LPRINT command.)

^1 So thats how to use the ANSI codes, but what do you do if you REALLY
^1want  to  use that quadruple size text mode, or redefine a character?
^1(And  here  I speak from experience, having written the LC10 , LC200,
^1and LC24-200 character defining programs, plug plug!) You have to dig
^1through  the manual, find the escape code sequence you need, and send
^1it  to the printer.  But NOT by using LPRINT, or PRINT #1 to PRT:  If
^1you do, what happens is that the printer driver sits there and goes -
^1"You  what?  Sorry guv, I don't follow that at all!  Lets pretend you
^1didn't  say  that,  and get on with the next bit".  The best that can
^1happen is that it just ignores your carefully written sequence.  More
^1likely,  the poor printer will get a belly full of data that IT won't
^1understand, and just sits there bleeping, or starts printing reams of
^1garbage.

^4 No, to  send  that sort of specialised escape code sequence, you are
^4forced  to  send  it directly to the PAR:  device, using the OPEN OUT
^4method  shown  earlier.  Using this method, you can send any data you
^4like, as an 8 bit byte.  LPRINT CHR$(0) becomes PRINT #1,0 , which is
^4a  good  example  of  something  that  LPRINT won't do.  You can then
^4achieve anything which your printer is capable of.
 
^6 But,  my  advice  is  this.  DONT, unless  you must.  Using the PAR:
^6device  ties  you  to  a fixed escape sequence output.  If you change
^6printer, or use escape code sequences that relate ONLY to one type of
^6printer, then if you want to distribute your program at all, there is
^6bound  to  be  someone whose printer will not accept the data, and so
^6one  less user for your application.  Even if you keep the program to
^6yourself, who is to say you will keep that printer forever?

^1 For a general program, make use of the ANSI effects available to you
^1through PRT:, and save anything else for your own experiments, unless
^1you  fancy  distributing your program with dozens of drivers to cater
^1for all those different printers.

^4 On a  general  note,  I  would  advise anyone NOT to bother with the
^4Printer  Driver  Generator  programs floating around in PD.  They are
^4utterly  useless  for  anything  other than text work, producing huge
^4drivers  which  DONT  cope  with graphics at all.  Far better find an
^4existing  driver  for a similar printer, and suffer any failings that
^4come with it.

^6 (I notice  that  many  Epson  drivers  interpret  BOLD codes to mean
^6doublestrike,  only  if you are in draft mode first, sending ESC E to
^6turn  it  on, and ESC F to turn it off.  This seems to have no effect
^6if you are already in NLQ mode on 9 pin printers, for instance, and I
^6prefer  to  get the real 'black' effect you get from ESC G and ESC H,
^6as  this  prints NLQ text in 4 passes (on my machine at least!).  So,
^6one  tip for the experts is to try something I did for the driver for
^6my  LC10,  which  is  to  use  a file ZAP program to edit the printer
^6driver  directly  on  disc.   (Only try this if you KNOW what you are
^6doing!)  Starting  with the EpsonXOld driver, I went through the file
^6byte  by  byte,  and  changed all ESC E to ESC G, and ESC F to ESC H.
^6(There  were two occurences) This gives me a great bold effect in NLQ
^6mode.)

^1 Anyhow, that  (briefly)  covers  the handling of text effects on the
^1printer.   Before I wind up, though, it would be a good idea to cover
^1the  things  that  have to be on the disc to make the printer work at
^1all.  This is a common problem for people who start out to make their
^1own stand-alone discs, but find that the printer seems not to work if
^1you have not booted up from workbench first.

^7 To print from a stand alone disc, you need:

^5   Devs                          (the directory)
^5   Devs/system-configuration
^5   Devs/printer.device
^5   Devs/parallel.device          (or serial.device if appropriate)
^5   Devs/printers                 (the directory)
^5   Devs/printers/<printerdriver>(the  printer  driver  will be called
^5                                 something  like EpsonX, NECpinwriter 
^5                                 or similar, and MUST be named in the
^5                                 system-configuration  file,  created
^5                                 by Preferences.)

^7.. as well as all the other files and directories your program needs.

^1 One final tip: some people find it hard to change the preferences on
^1their  own non-workbench discs.  Try this..  Boot up your own disc in
^1drive  DF0:,  holding  down  CTRL and D, to stop the startup-sequence
^1from running.  When the CLI prompt appears, put the Workbench disc in
^1DF1:,  and  when  it  is  ready, type DF1:Prefs/preferences (which is
^1where  preferences lives in WB1.3) Edit the preferences until you are
^1happy   with  them,  then  when  you  save,  the  program  saves  the
^1system-configuration file to your own disc.

^4Remember, even if it doesn't work first time, you will learn a lot by
^4trying to fix it!

^3                          Happy printing. 

^4                                                               Jeff.
^1P.S. from Jeff, to turn on NLQ, use:-

^1Print#1,CHR$(27)+"*z"+CHR$(34)+"z"

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