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The null character (also null terminator) is a character with the value zero, present in the ASCII and Unicode character sets, and available in nearly all mainstream programming languages. The original meaning of this character was like NOP — when sent to a printer or a terminal, it does nothing (some terminals, however, incorrectly display it as space). On punched tapes, this character is represented with no holes at all, so a new unpunched tape is initially filled with null characters.
On many computer and data terminal keyboards, it was possible to type a null character by holding down the Control key and pressing "@" (which usually required also holding Shift and pressing another key such as "2" or "P"). Consequently, in some contexts, the null character is represented visually as "^@". In other contexts, it is represented as a subscript, single-em-width "NUL". In Unicode, there is a character for visual representation of null character, "symbol for null", U+2400 () — not to be confused with the actual null character, U+0000.
The character has special significance in C and its derivatives, where it serves as a reserved character used to signify the end of strings. The null character is often represented as "
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