Upgrade Guide - Prolifics

Processing Terminal OutputHow Panther Handles OutputPanther uses a delayed write output scheme to minimize unnecessary and redundantoutput to the display. No output at all is done until the display must be updated, eitherbecause keyboard input is solicited or the library function sm_flush is called. Instead,the runtime system does screen updates in memory and keeps track of the displaypositions. Flushing begins when the keyboard is opened; but if you type a characterwhile flushing is in progress, the runtime system processes it before sending any moreoutput to the display. Therefore, you can type ahead on slow displays. You can forcethe display to be updated by calling sm_flush.Graphics Characters and Alternate Character SetsMany terminals support the display of graphics or special characters through alternatecharacter sets. Panther provides 8-bit alternate character sets–for example, those thattranslate from IBM PC extended character to Latin-1. These tables can be installed bycalling the library function sm_xlate_table. Control sequences switch the terminalamong the various sets, and characters in the standard ASCII range are displayeddifferently in different sets. Panther supports 8-bit to 7-bit translations via the MODExand GRAPH entries in the video file.The seven MODEx sequences (where x is 0 to 6) switch the terminal into a particularcharacter set. MODE0 must be the normal character set. The GRAPH command mapslogical characters to the mode and physical character necessary to display them. Itconsists of a number of entries whose form is logical value = mode physical-character.When Panther needs to output logical value it first transmits the sequence that switchesto mode, then transmits physical-character. It keeps track of the current mode to avoidredundant mode switches when a string of characters in one mode (such as a graphicsborder) is being written. MODE4 through MODE6 switch the mode for a single characteronly.B-6 JAM Documentation: Internal I/O Processing