{
  "id": "terminal-csi/ich",
  "family": "terminal-csi",
  "slug": "ich",
  "title": "CSI ICH / DCH — Insert / Delete Character",
  "summary": "ICH (final '@') inserts Pn blank characters at the cursor, shifting the rest of the line right (characters pushed past the right margin are lost); DCH (final 'P') deletes Pn characters at the cursor, shifting the remainder of the line left with blanks appearing at the right margin. Both default Pn to 1 and act only on the current line.",
  "kind": "control-sequence",
  "aliases": [
    "ICH",
    "DCH",
    "insert character",
    "delete character",
    "ESC [ @",
    "ESC [ P"
  ],
  "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 @ = Insert Ps (Blank) Characters (ICH); CSI Ps P = Delete Ps Characters (DCH). Default Ps = 1."
    },
    {
      "claim_ref": "ext.params",
      "source_url": "https://ecma-international.org/publications-and-standards/standards/ecma-48/",
      "source_version": "ECMA-48 5th ed. 1991 (ISO/IEC 6429), clauses 8.3.64 (ICH) and 8.3.26 (DCH)",
      "note": "ECMA-48 defines ICH (final '@') and DCH (final 'P') operating on the active line, default Pn 1."
    }
  ],
  "see_also": [
    "terminal-csi/ech",
    "terminal-csi/il",
    "terminal-csi/el"
  ],
  "ext_type": "terminal-escape@1",
  "ext": {
    "csi_or_osc": "CSI",
    "command_number": "ICH",
    "frame": {
      "introducer_7bit": "\u001b[",
      "introducer_7bit_readable": "ESC [ (0x1B 0x5B)",
      "introducer_8bit": "›",
      "introducer_8bit_readable": "0x9B (single-byte CSI, 8-bit C1)",
      "note": "CSI + single Pn + final byte: '@' insert-char (0x40), 'P' delete-char (0x50). Pn defaults to 1; scoped to the current line."
    },
    "terminator": "none",
    "terminator_detail": {
      "note": "No string terminator; the CSI sequence ends at its final byte. Parameters Ps are decimal, ';' (0x3B) separated."
    },
    "params": [
      {
        "id": "ich",
        "anchor": "#ich",
        "name": "ICH — Insert Character (@)",
        "meaning": "CSI Pn @ inserts Pn blanks at the cursor; characters to the right shift right by Pn and any pushed past the right margin are lost. The cursor does not move.",
        "required": true,
        "byte_sequence_ST": "\u001b[3@",
        "byte_sequence_ST_readable": "ESC [ 3 @   ==  \\x1b[3@   (insert 3 blanks)",
        "subparams": []
      },
      {
        "id": "dch",
        "anchor": "#dch",
        "name": "DCH — Delete Character (P)",
        "meaning": "CSI Pn P deletes Pn characters at the cursor; the remainder of the line shifts left and blanks (current background) appear at the right margin.",
        "required": false,
        "byte_sequence_ST": "\u001b[3P",
        "byte_sequence_ST_readable": "ESC [ 3 P   ==  \\x1b[3P   (delete 3 chars)",
        "subparams": []
      }
    ],
    "gotchas": [
      "ICH/DCH operate within the single current line; they never affect other rows (use IL/DL for line-level edits).",
      "Inserted/exposed cells take the current SGR background color.",
      "Characters shifted past the right margin by ICH are discarded, not wrapped.",
      "ICH does NOT move the cursor; the inserted blanks appear AT the cursor and the cursor stays put.",
      "Distinct from ECH (CSI X) which erases in place WITHOUT shifting the rest of the line."
    ],
    "v1_smoke_test": {
      "asserts": "ICH ('@') and DCH ('P') render as byte-exact single-parameter CSI sequences.",
      "behavioral_conformance": "deferred to v2."
    }
  },
  "updated": "2026-05-29T00:00:00Z"
}