DA Device Attributes

With Ps left out or 0, DA asks the terminal to identify itself, and the terminal answers CSI ? Ps ; … c. DEC STD 070 defines what the answer means. The first parameter is the kind of device and the level of DEC’s architecture it conforms to: 61 to 69 are character-cell displays, so 62 is one conforming to level 2. The rest name extensions it has, such as 22 for ANSI color.

With any other Ps, ECMA-48 says DA does the opposite: it identifies the sender, with Ps as a device type code. A terminal receiving one has not been asked anything. DEC STD 070 likewise makes only an omitted or zero parameter a request, and xterm answers only those.

What the terminal says about itself is the host program’s choice. libghostty-vt asks its host and encodes whatever comes back, and the cases here run with the answers Ghostty gives, describing itself in its source as a VT220: level 2, with ANSI color. See the notation page.

Two DEC extensions ask for more:

• CSI > c is secondary DA, the VT510 manual’s DA2. The answer CSI > Pp ; Pv ; Pc c gives the terminal type, the firmware version and the ROM cartridge.
• CSI = c is tertiary DA, DA3. The answer is a control string, DCS ! | D…D ST, holding the terminal’s unit ID as four hexadecimal pairs.

DECID, ESC Z, is the VT52-era way of asking the same thing as DA. The VT510 manual says it makes the terminal send its DA answer, and that programs should use DA instead.

Validation

DA-1: Primary attributes

\e[c

|_____|
reply \e[?62;22c

DA-2: With the parameter zero

\e[0c

|_____|
reply \e[?62;22c

DA-3: Secondary attributes

\e[>c

|_____|
reply \e[>1;10;0c

DA-4: Tertiary attributes

\e[=c

|_____|
reply \eP!|00000000\e\\

DA-5: A non-zero parameter is not a request

\e[1c     # identifies the host; asks nothing

|_____|
reply none

libghostty-vt answers it as if it were a request. Its DA dispatch in stream.zig chooses primary, secondary or tertiary from the intermediate byte alone and never looks at the parameter. ECMA-48 makes a non-zero DA an identification of its sender, DEC STD 070 makes only an omitted or zero parameter a request, and xterm replies only when the parameter is zero or left out.

DA-6: DECID

\eZ

|_____|
reply \e[?62;22c