DEC STD 110

This document, DEC STD 110 REV. B, establishes the standard for "Escape Sequences" used by Digital Equipment Corporation (DEC) terminals and software, specifically for new hardware like the VT50 and future CRT terminals.

Key points of the standard include:

• Definition of ESC: The Escape character (ESC) is defined as ASCII 33 (octal 33). Older terminals using 175 or 176 octal for ESC must convert these to 33 octal before processing.
• Prohibition on Echoing: Indiscriminate echoing of ESC (33 octal) is strictly prohibited.
• Visible Confirmation: If visible confirmation that ESC has been received is desired, it must be a single dollar sign ($, ASCII 44 octal).
• Sole Purpose of ESC: In "ESC-Mode" (the standard's intended mode), the ESC character solely functions as the initial delimiter of an escape sequence and should not carry any other meaning (e.g., it should not act as a "break sequence" by itself).
• Sequence Structure: An ESC sequence begins with one ESC character, followed by zero or more "intermediate characters" (ASCII 40-57 octal), and ends with one "final character" (ASCII 60-176 octal). Characters in the range 0-37 octal or 177 octal are prohibited within an ESC sequence.
• Compatibility: The standard aims to be compatible with ANSI extension proposals for escape sequences but notes incompatibilities with older DEC systems like the Model 37 Teletype and VT05.
• DEC-Specific Sequences: DEC reserves specific two-character ESC sequences (ESC followed by final characters in the 60-77 octal range) for its own private control functions, which ANSI will not standardize.
• Implementation: Software should be "table-driven" to allow for future changes and adoption of official ANSI standards.