OpenVMS Terminal Fallback Utility Manual

This document describes the OpenVMS Terminal Fallback Utility (TFU), which serves as the user interface for the VMS Terminal Fallback Facility (TFF). The primary purpose of TFF is to provide transparent character conversion for terminals and to enable character compose emulation. This facility helps bridge the gap between incompatible character sets and keyboards, allowing terminals to display characters they normally wouldn't, or replacing them with the closest visual equivalent (fallback). It also enables users to create special characters by combining existing ones through "compose sequences" (e.g., Ctrl/K followed by two characters).

Key functionalities and setup involve:

• Enabling TFF: System managers must enable TFF on the VMS operating system by running TFF$STARTUP.COM to load the fallback terminal driver (FBDRIVER).
• Loading Tables: Character conversion tables (fallback) and compose sequence tables (e.g., LATIN_1 for Digital applications) must be loaded into the system's nonpaged dynamic memory pool using the LOAD TABLE command. The master library for these tables is SYS$SYSTEM:TFF$MASTER.DAT.
• Setting Defaults: Default fallback and compose tables can be established system-wide using SET DEFAULT_TABLE for user convenience.
• Managing Terminal Parameters: TFU allows system managers and individual users to set, change, and display TFF terminal parameters for specific terminals using SET TERMINAL/FALLBACK. Options include enabling 8-bit character input (ACCEPT), managing auto-compose keys, specifying character sets (GX_DEFAULT), suspending TFF intervention (SUSPEND), and assigning specific tables (TABLE:table-name).
• Monitoring: Commands like SHOW STATISTICS, SHOW TABLES, and SHOW TERMINAL/FALLBACK provide information on memory usage, loaded tables, and terminal-specific TFF settings.
• Privileges: Operations such as loading/unloading tables and setting default tables require operator (OPER) privilege.

The document is intended for VMS system managers and users who need to manage character conversion and terminal behavior for various character sets, including National Replacement Character (NRC) sets and the Multinational Character Set (MCS).