The PS and SPY drivers

This part has been written by Larry Bartholdi.

One one the restrictions of BGI was that it could handle displays, but not printers. To overcome this limitation, some people developed ``printer packages'' for BGI. Although they derive from a real need, they are almost useless in that the force a complete re-write of the high-level code, linking with extra libraries, etc. By contrast, the solution I propose is a simple ``plug-and-play'': the driver should be recoginsed by any system using BGI that allows user-supplied drivers to be installed (see INSTALL-USER-DRIVER). The price to pay is, of course, that the driver produces only PostScript output. This postScript can then be send to a laser printer, inserted in a text document, or converted to another format or device. See for instance GNU's ``ghostscript''.

The drivers are written in C. This makes them very easy to change, while requiring very little extra space. An interface to the C code, written in assembly language is provided. Users are free to write their own BGI drivers using this system.



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