Plotter output may be produced by an interactive program running on a machine directly connected to a hardcopy device. For example, GKSGRAL at CERN supports Hewlett Packard pen plotters, VERSATEC electrostatic and thermal plotters, and any laser printer
driven via the PostScript interface. (See the latest version of the include file GTSDEV for a complete up-to-date list of supported devices.)
In the case of VERSATEC or PostScript, an intermediate plot file is generally produced which must be queued to the device. However, use of an HP plotter normally assumes that the device is connected directly in parallel with the terminal line, and it is activated by special escape sequences sent by the driver, but it is also possible to produce an HP plotter file by specifying a connection identifier of conid = (100 + n), where n is a small integer greater than 1. This causes the output to be written to FORTRAN Logical Unit number n, and the file has the name PLxxxx.PLT, where 'xxxx' indicates the workstation type. Some laser printers do not support PostScript but do, in fact, support the Tektronix 4014 protocol. In this case it is possible to capture the 4014 escape codes on a file which is later sent to the printer. In any case, to capture the graphics on a file, first open a file on unit n, and then open the corresponding GKS workstation with a conid of (100 + n).
Note that use of a hardcopy device via an interactive program has the advantage that the application can inquire the specific device characteristics, and thus tailor the output accordingly.