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Those never working Esc sequences!

Many printers come with a manual that explains which Esc sequence causes which action on the printer. But there happen weird things when you try to send these sequences to your printer, either it does nothing, or it does something completely different. There is a reason, the Amiga printer drivers. These drivers are made in a way that they only understand a certain set of ANSI Esc sequences, not the special ones defined (differently) by the various printer manufacturers. The purpose is that every application on the Amiga just uses this one standard set of control sequences and this way doesn't need to know which printer is actually connected. The printer driver then translates these standard sequences into the special sequences a certain printer understands. A list of the available ANSI Esc sequences is found in the current Workbench manuals (or older AmigaDOS manuals). Now if you want to issue a control sequence to the printer that's not available as an ANSI command, you have two possibilities to achieve this:
  1. Bypass the printer driver (that would unsuccessfully try to interpret the sequence) and send your output only during this sequence to `PAR:' (or `SER:', respectively). For this you have to close and open printer output channels very often which is rather tedious, and you have to know where (`PAR:' or `SER:') your printer is connected.
  2. Use a special ANSI sequence, made exactly for this case:
    where `<n>' is the decimally typed number of bytes in the string `<x>', which actually contains your special printer sequence. This ANSI sequence tells the printer driver to not interpret or translate the next `<n>' bytes.
But both methods have one big disadvantage when used in an application program: You lose the printer independency! If you stick to ANSI sequen- ces, you can output to any printer on earth, as long as there is an Amiga printer driver for it. If you start to use special control sequences, your program will be tied to this single printer model and will not be usefull for any other (or you would have to provide some dozen new printer drivers for your application).

Dr. Peter Kittel, peterk@cbmger.de.so.commodore.com

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