When electromechanical teleprinters were used as computer output devices, one or more null characters were sent at the end of each printed line to allow time for the mechanism to return to the first printing position on the next line.
Today the character has much more significance in the programming language C and its derivatives and in many data formats, where it serves as a reserved character used to signify the end of a string,[6] often called a null-terminated string.
Thus the ability to type it (in case of unchecked user input) creates a vulnerability known as null byte injection and can lead to security exploits.
On some keyboards, one can enter a null character by holding down Ctrl and pressing @ (on US layouts just Ctrl+2 will often work, there being no need for ⇧ Shift to get the @ sign).
In documentation, the null character is sometimes represented as a single-em-width symbol containing the letters "NUL".