2.2 The IBM 7171 ASCII Device Attachment Control Unit - Index of

Terminal Hetlder Information: The first part of the TDT is the Terminal HeaderInformation. The Terminal Header has ten items and each item occupies two bytesof storage except for the Screen Size Definitions which require eight bytes. Thesetwenty six bytes provide basic information about the specific terminal.ItemDefinition of Stored Data1 Status Flags2 Pointer·to Initial Parse Table Entry3 Pointer to First CSS Pointer4 Cursor Base5 Pointer to Host Translation Table Addresses6 Pointer to Terminal Translate Tables7 Pointer to Reset Character String8 Delay9 Pointer to Set Graphic Rendition String10 Screen Size DefinitionsA description of each of these fields follows:1. Flags.The Flags parameter can be used to set bit flags which describe special terminalcharacteristics. The following flags can be specified:Byte 0 FlagsBits MeaningX ' 80' Hardcopy terminal.X '40' Can dynamically switch from APL to non-APL and back underprogram control (usually SI and SO characters).X' 10' Type of APL keyboardOn - bit paired terminal.Off - typewriter paired terminal.X ' 08' Highlighting can be performed.X ' 04' Highlighting is a mode of output, where characters written after anescape sequence are displayed highlighted, rather than an attributebyte, where characters in the following screen positions changedisplay without themselves being rewritten.Byte 1 FlagsBits MeaningX '80' New format terminal header containing physical and logical screensize information.4-28 IBM 7171 Reference Manual and Programming Guide