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See also Null (SQL), Null reference, Null pointer, Null pointer exception

Null may refer to:

• Null (SQL) (or NULL), a special marker and keyword in SQL indicating that something has no value

• Null character, the zero-valued ASCII character, also designated by

  , often used as a terminator, separator or filler. This symbol has no visual representation

• Null device, a special computer file, named

  /dev/null

  on Unix systems, that discards all data written to it

• Null modem, a specially wired serial communications cable

• Null pointer (sometimes written

  NULL

  ,

  nil

  , or

  None

  ), used in computer programming for an uninitialized, undefined, empty, or meaningless value

• Null string, the unique string of length zero (in computer science and formal language theory)

• Null (mathematics), a zero value in several branches of mathematics

• Null set, a set that is negligible in some sense

**Also an older term for the empty set

• Null cipher, a ciphertext symbol

• Null hypothesis, a concept in statistical hypothesis testing
• Null result, the absence of a hypothesized effect in the outcome of a scientific experiment

• Null and void, having no legal validity

• Ø (disambiguation)
• Null symbol (disambiguation)
• 0 (disambiguation)
• Nil (disambiguation)
• Nul (disambiguation)