VT220

This reference manual provides comprehensive programming information for the VT220 video display terminal, intended for users with basic computer programming knowledge.

The document is organized into four main chapters and two appendices:

• Terminal Overview: Introduces the VT220 terminal's general-purpose nature, its two-box design (monitor/system unit and keyboard), and its use of ANSI Standard functions. It details key display characteristics (e.g., monochrome, 24 rows, 80/132 columns, pixel resolutions), text capabilities (multiple character sets including DEC Multinational and down-line loadable, user-definable keys, various character attributes), communication features (asynchronous to 19.2K bps, EIA RS232C, 7/8-bit format), operating states (Set-Up, On-Line, Local), and operating modes (VT100, VT200 with 7/8-bit controls, and VT52 mode), each offering different levels of compatibility and functionality.
• Character Encoding: Describes the 8-bit character encoding scheme and 7-bit code extension techniques compliant with ANSI and ISO standards. It covers 7-bit ASCII and 8-bit code tables, C0/C1 control characters, and graphic character sets such as the DEC Multinational Character Set, U.K. National Set, DEC Special Graphics Set, and Down-Line Loadable Character Set. It also explains the format of control functions, including escape sequences, control sequences, and device control strings.
• Transmitted Codes: Details the codes generated and transmitted by the terminal to a program, including those from the main keypad (alphanumeric and function keys), editing keypad, auxiliary keypad, and top-row function keys. It differentiates between codes generated in ANSI-compatible (VT200, VT100) and VT52 modes, and discusses features like autorepeat and keyboard lock/unlock conditions.
• Received Codes: Outlines how the terminal responds to codes received from an application or host system. This includes processing graphic and control characters, escape sequences, and device control strings. It covers a wide array of control functions for character set selection, terminal mode settings (e.g., Keyboard Action, Insert/Replacement, Send-Receive, Column, Scrolling, Auto Wrap), cursor positioning, tab stops, character and line attributes, editing (insert/delete characters/lines, erase), printing, user-defined keys (DECUDK), and down-line loadable character sets (DRCS). It also describes reports (Device Attributes, Device Status, Identification) and terminal reset procedures.
• Appendices: Provide information on differences between the VT220 and VT102 terminals (when VT220 operates in VT100 mode) and list additional VT220 documentation.