Overview
ISO/IEC 6429:1992 - "Information technology - Control functions for coded character sets" standardizes a comprehensive repertoire of control functions and their coded representations for use with 7‑bit, extended 7‑bit, 8‑bit and extended 8‑bit coded character sets when those codes are structured according to ISO 2022. The standard defines how control functions (for example escape sequences and control sequence introducers) behave when embedded in character streams and how character‑imaging devices should interpret them. The third edition adds facilities for handling bi‑directional text (left‑to‑right and right‑to‑left scripts).
Key topics and technical requirements
- Scope: Applies to control functions carried inside CC‑data‑elements and assumes device architecture described in clause 6 (presentation/data components, active positions, implicit/explicit movement).
- Control repertoire: A large set of standardized control functions (ESC, CSI, SGR, NEL, HT, LF, etc.) and control sequences with parameter formats and defaults.
- Coding models: Support for 7‑bit and 8‑bit encodings that follow ISO 2022 structure; definitions of independent control functions, control strings and device control strings.
- Modes and interaction: A mode model (e.g., Control Representation Mode, Bi‑Directional Support Mode, Format Effector modes) that governs interpretation and interactions among control functions.
- Conformance: Defines full and limited conformance, plus device conformance requirements - devices must document which control functions they originate, receive and present. Distinguishes originating vs receiving device responsibilities.
- Device concepts: Abstract device components (presentation, data, editor/formator functions), selected/qualified areas, tabulation/fields and auxiliary I/O.
- Annexes: Coding examples, formator/editor guidance, text composition considerations and implementation‑dependent features.
Applications and who uses it
ISO/IEC 6429 is practical for implementers and integrators working with text and terminal control:
- Terminal emulators, console and shell developers (escape/CSI handling)
- Printer and character‑imaging device manufacturers
- Firmware and embedded systems that process control sequences
- Text rendering and layout engines that must support bidirectional scripts
- Protocol designers and application developers exchanging CC‑data elements
- Internationalization (i18n) engineers ensuring correct directionality and control behavior
Implementing ISO/IEC 6429 helps ensure consistent behavior of escape sequences, control functions, and mode transitions across systems and devices, improving interoperability of text interchange and device control.
Related standards
- ISO 2022 - character code structure referenced by ISO/IEC 6429
- ECMA‑48 - ECMA equivalent (original development basis)
- ISO 2375 - registration of selected facility sets for interchange
Keywords: ISO/IEC 6429, control functions, escape sequences, control sequence introducer (CSI), ISO 2022, bi‑directional text, character‑imaging devices, terminal emulation, conformance.
