Devices Supported by PLPLOT on the Amiga

At run time the user specifies whether the graphics should be drawn on the Amiga's screen or stored in a device dependent file. If the Amiga screen is selected then a backdrop, borderless window is opened on a high resolution, interlaced screen. Two menus are available for screen and graphics control. When the window is first opened only two menu selections are available. These are the Interrupt selection under the Graphics Control menu (Interrupt can also be selected by typing CTRL-C) and the Screen to Back selection under the Screen Control menu (Screen to Back can also be selected to by holding the right Amiga key down and then hitting F). The Screen to Back selection will move the graphics screen behind any other screens you may have open. The Interrupt selection will suspend any drawing operations. After the Interrupt selection is made all other menu selections are enabled. Under the Screen Control menu the user can then select Screen to Back, Clear Screen, and Close Screen. The Screen to Back selection has already been discussed. The Clear Screen and Close Screen operations can also be selected from the keyboard by holding down the right Amiga key and typing either C or Q. The Clear Screen selection, as you've probably guessed, clears the screen. The Close Screen selection closes the screen, calls <#158#>plend<#158#> (page #plend#159>) and then calls the exit routine to end program execution. The Close Screen selection does not return control back to the user's main program. It should be used only to gracefully abort the program. Under the Graphics Control menu the only enabled menu selection is Continue (also selectable by hitting the RETURN key). This will continue program execution at the point where it was suspended. When a program uses PLPLOT to create a sequence of graphs then PLPLOT will automatically wait for the Continue selection before erasing one graph and starting the next one. After the last graph is displayed (or the first one, if only one is being drawn) PLPLOT will again wait for a Continue selection. The screen will then be closed and control returned to the user's program. This is the preferred method of closing the screen (as opposed to the Close Screen selection).

After one graph is complete, the user can move the Screen to Back to get WorkBench access and then use the GraphicDump (or similar) program to obtain hardcopy. However, if you have a fairly high resolution printer or plotter best results will be obtained if you use a specific device driver. Three device drivers are supplied with PLPLOT. These drivers can be used as guidelines in writing your own drivers. The supplied drivers provide support for the following graphics languages:

The HP LaserJet II does not actually support any type of vector graphics language. Instead a bit map is created in memory and when the graph is completed the bit map is written to a file (along with some HP specific control sequences). To keep the memory requirements (for both the Amiga and LaserJet II) low this driver only supports the 150 dot per inch mode of the laser printer. The file sizes can be rather large if multiple graphs are produced from a single main program.

Tektronix and imPRESS devices do have vector drawing support and are the simplest type devices to write drivers for. The graphics commands are written to a file on the fly, without the need for a bit map. imPRESS is a page description language for IMAGEN printers. After the graphics file is created just copy it to the appropriate device (do not send the file to prt: use either ser: or par:).