{
  "id": "terminal-csi/da",
  "family": "terminal-csi",
  "slug": "da",
  "title": "CSI DA — Device Attributes (primary / secondary / tertiary)",
  "summary": "DA queries the terminal's identity. Primary DA (CSI c or CSI 0 c, final 'c') asks what the terminal is; the reply CSI ? ... c lists a model class and feature codes. Secondary DA (CSI > c) reports terminal type, firmware version, and ROM cartridge as CSI > Pp ; Pv ; Pc c. Tertiary DA (CSI = c) requests a unit ID, replied via a DCS string (DECRPTUI).",
  "kind": "control-sequence",
  "aliases": [
    "DA",
    "DA1",
    "DA2",
    "DA3",
    "device attributes",
    "primary DA",
    "secondary DA",
    "ESC [ c",
    "ESC [ > c"
  ],
  "status": "standard",
  "verification": "verified",
  "tier": "B",
  "source_url": "https://invisible-island.net/xterm/ctlseqs/ctlseqs.html",
  "source_version": "xterm ctlseqs, patch #410, 2026/04/19",
  "retrieved_date": "2026-05-29",
  "attribution": [
    {
      "claim_ref": "#summary",
      "source_url": "https://invisible-island.net/xterm/ctlseqs/ctlseqs.html",
      "source_version": "xterm patch #410, 2026/04/19",
      "note": "xterm ctlseqs: CSI Ps c = Send Device Attributes (Primary DA); CSI > Ps c = Secondary DA (reports type;version;cartridge); CSI = Ps c = Tertiary DA (DECRPTUI unit id). Primary reply CSI ? 6 1/6 2/... ; ... c."
    },
    {
      "claim_ref": "ext.params",
      "source_url": "https://vt100.net/docs/vt510-rm/DA1.html",
      "source_version": "DEC VT510 Programmer Reference, DA1/DA2/DA3, retrieved 2026-05-29",
      "note": "DEC VT510 manual: Primary DA (CSI c) reports the terminal's service class and supported features; Secondary DA (CSI > c) reports identification code, firmware version, and ROM cartridge."
    }
  ],
  "see_also": [
    "terminal-csi/dsr"
  ],
  "ext_type": "terminal-escape@1",
  "ext": {
    "csi_or_osc": "CSI",
    "command_number": "DA",
    "frame": {
      "introducer_7bit": "\u001b[",
      "introducer_7bit_readable": "ESC [ (0x1B 0x5B)",
      "introducer_8bit": "›",
      "introducer_8bit_readable": "0x9B (single-byte CSI, 8-bit C1)",
      "note": "CSI + optional prefix ('>' secondary, '=' tertiary) + Ps + final byte 'c' (0x63). Replies are CSI ? ... c (primary) or CSI > ... c (secondary)."
    },
    "terminator": "none",
    "terminator_detail": {
      "note": "No string terminator; the CSI sequence ends at its final byte. Parameters Ps are decimal, ';' (0x3B) separated."
    },
    "params": [
      {
        "id": "primary",
        "anchor": "#primary",
        "name": "Primary DA (DA1) — CSI c",
        "meaning": "CSI c (or CSI 0 c) asks the terminal to identify its class and features. A VT100-class terminal replies e.g. CSI ? 1 ; 2 c; an xterm-class one CSI ? 6 2 ; ... c (62 = VT220 level, followed by feature numbers).",
        "required": true,
        "byte_sequence_ST": "\u001b[c",
        "byte_sequence_ST_readable": "ESC [ c   ==  \\x1b[c   (also \\x1b[0c; reply \\x1b[?62;...c)",
        "subparams": []
      },
      {
        "id": "secondary",
        "anchor": "#secondary",
        "name": "Secondary DA (DA2) — CSI > c",
        "meaning": "CSI > c reports terminal type, firmware version, and ROM cartridge: reply CSI > Pp ; Pv ; Pc c (e.g. Pp identifies the model, Pv the version).",
        "required": false,
        "byte_sequence_ST": "\u001b[>c",
        "byte_sequence_ST_readable": "ESC [ > c   ==  \\x1b[>c   (reply \\x1b[>0;276;0c style)",
        "subparams": []
      },
      {
        "id": "tertiary",
        "anchor": "#tertiary",
        "name": "Tertiary DA (DA3) — CSI = c",
        "meaning": "CSI = c requests a unit ID; the terminal replies with a DCS report (DECRPTUI), DCS ! | <hex id> ST.",
        "required": false,
        "byte_sequence_ST": "\u001b[=c",
        "byte_sequence_ST_readable": "ESC [ = c   ==  \\x1b[=c   (reply via DCS DECRPTUI)",
        "subparams": []
      }
    ],
    "gotchas": [
      "The DA reply arrives on the terminal's INPUT stream; read with a timeout to avoid blocking.",
      "Primary DA is the most-used handshake: emulators report a VT220/VT320-class set of feature codes that programs use to gate capabilities. Do NOT assume a specific code list — parse defensively.",
      "Secondary DA's 'version' field is emulator-defined (e.g. xterm reports its patch number); it is not a reliable real-firmware version.",
      "Tertiary DA replies via a DCS (Device Control String), not a CSI, so a CSI-only parser will miss it.",
      "CSI c with no parameter equals CSI 0 c (primary DA)."
    ],
    "v1_smoke_test": {
      "asserts": "Primary (CSI c), secondary (CSI > c), and tertiary (CSI = c) DA requests render as byte-exact CSI sequences; reply shapes documented.",
      "behavioral_conformance": "deferred to v2."
    }
  },
  "updated": "2026-05-29T00:00:00Z"
}