"null character" meaning in English

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "null",
        "3": "character"
      },
      "expansion": "null + character",
      "name": "com"
    }
  ],
  "etymology_text": "null + character",
  "forms": [
    {
      "form": "null characters",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "null character (plural null characters)",
      "name": "en-noun"
    }
  ],
  "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"
        }
      ],
      "glosses": [
        "A control character with the value zero and no visual representation."
      ],
      "id": "en-null_character-en-noun-E1Qd9QFO",
      "links": [
        [
          "computing",
          "computing#Noun"
        ],
        [
          "control character",
          "control character"
        ],
        [
          "zero",
          "zero"
        ]
      ],
      "raw_glosses": [
        "(computing) A control character with the value zero and no visual representation."
      ],
      "synonyms": [
        {
          "tags": [
            "symbol"
          ],
          "word": "␀"
        }
      ],
      "topics": [
        "computing",
        "engineering",
        "mathematics",
        "natural-sciences",
        "physical-sciences",
        "sciences"
      ]
    }
  ],
  "word": "null character"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "null",
        "3": "character"
      },
      "expansion": "null + character",
      "name": "com"
    }
  ],
  "etymology_text": "null + character",
  "forms": [
    {
      "form": "null characters",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "null character (plural null characters)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English compound terms",
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "en:Computing"
      ],
      "glosses": [
        "A control character with the value zero and no visual representation."
      ],
      "links": [
        [
          "computing",
          "computing#Noun"
        ],
        [
          "control character",
          "control character"
        ],
        [
          "zero",
          "zero"
        ]
      ],
      "raw_glosses": [
        "(computing) A control character with the value zero and no visual representation."
      ],
      "topics": [
        "computing",
        "engineering",
        "mathematics",
        "natural-sciences",
        "physical-sciences",
        "sciences"
      ]
    }
  ],
  "synonyms": [
    {
      "tags": [
        "symbol"
      ],
      "word": "␀"
    }
  ],
  "word": "null character"
}