GPCLEAR clears the current graphics device.
INPUT PARAMETERS
DEVICE Device|name|x size;y size|color type
PROGRAM DESCRIPTION
This program clears the graphics device. On an interactive
device, the screen is erased. On a hardcopy device, the
next plot will be on a new page.
ERROR MESSAGES
[GPCLEAR -1] Fatal error initializing TAE.
[GPCLEAR -2] Fatal error reading TAE parameters.
[GPCLEAR -3] Fatal error initializing GEMPLT.