".dat" meaning in English

{
  "etymology_text": "From the first three letters of \"data\" (data).",
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "noun",
        "3": "uncountable"
      },
      "expansion": ".dat (uncountable)",
      "name": "head"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Computing",
          "orig": "en:Computing",
          "parents": [
            "Technology",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "derived": [
        {
          "word": ".dat file"
        }
      ],
      "glosses": [
        "An extension for a data file."
      ],
      "id": "en-.dat-en-noun-prIcCjbE",
      "links": [
        [
          "computing",
          "computing#Noun"
        ],
        [
          "data file",
          "data file"
        ]
      ],
      "raw_glosses": [
        "(computing) An extension for a data file."
      ],
      "tags": [
        "uncountable"
      ],
      "topics": [
        "computing",
        "engineering",
        "mathematics",
        "natural-sciences",
        "physical-sciences",
        "sciences"
      ]
    }
  ],
  "word": ".dat"
}

{
  "derived": [
    {
      "word": ".dat file"
    }
  ],
  "etymology_text": "From the first three letters of \"data\" (data).",
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "noun",
        "3": "uncountable"
      },
      "expansion": ".dat (uncountable)",
      "name": "head"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English entries with incorrect language header",
        "English lemmas",
        "English nouns",
        "English terms spelled with .",
        "en:Computing"
      ],
      "glosses": [
        "An extension for a data file."
      ],
      "links": [
        [
          "computing",
          "computing#Noun"
        ],
        [
          "data file",
          "data file"
        ]
      ],
      "raw_glosses": [
        "(computing) An extension for a data file."
      ],
      "tags": [
        "uncountable"
      ],
      "topics": [
        "computing",
        "engineering",
        "mathematics",
        "natural-sciences",
        "physical-sciences",
        "sciences"
      ]
    }
  ],
  "word": ".dat"
}