DECKBUM Keyboard Usage Mode
Choose between typewriter keys and data processing keys.
CSI ? 68 h/l
- DEC STD 070
- §6.7.5 Set/Reset Keyboard Usage Mode, p. 6-57
- VT510
- DECKBUM—Typewriter or Data Processing Keys
Mode 68 switches a DEC keyboard between typewriter keys (reset) and data processing keys (set), which put the characters programmers use, such as braces and brackets, where a national keyboard would have its own letters. It changes only what the keyboard sends, which this site cannot press, so nothing on the screen changes. DEC STD 070 calls it a user preference, which software should set only when the user asks.
xterm recognizes the mode and ignores it (charproc.c); DECRQM reports it as permanently reset, 4, at level 3 and up, and xterm is a VT420 by default (do_dec_rqm). esctest2 expects the mode to change and lists xterm as not supporting it; the cases follow xterm.
libghostty-vt does not have the mode: mode 68 is not in its table in modes.zig, so DECRQM reports it as not recognized, 0. The two DECRQM cases are known differences.
Support
| Terminal | Version | Support | Notes |
|---|---|---|---|
| VT220 | manual, 2nd ed., 1984 | No | not in the manual |
| VT510 | manual, 1st ed., 1993 | Yes | DECKBUM |
| xterm | patch 412, xterm-411a | No | recognized and ignored; DECRQM reports it as permanently reset |
| libghostty-vt | 0f171f6 | No | not in its mode table; DECRQM reports 0 (DECKBUM-1, DECKBUM-2) |
| ConEmu | build 230724, its documentation | No | not in ConEmu’s list, ANSI escape codes |
Validation
DECKBUM-1: Reported as permanently reset
\e[?68$p
|_____|
reply \e[?68;4$y
DECKBUM-2: Even after it is set
\e[?68h
\e[?68$p
|_____|
reply \e[?68;4$y
DECKBUM-3: Nothing on the screen changes
A
\e[?68h
B
|AB___|