DECKBUM Keyboard Usage Mode

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.

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___|