, an end-of-transmission character
(EOT) is a transmission control character
used to indicate the conclusion of a transmission that may have included one or more texts and any associated message
Note: An EOT is often used to initiate other functions, such as releasing circuits, disconnecting terminals, or placing receive terminals in a standby condition. In Unix-like systems, the character is used to signal an end-of-file when typing at a terminal or terminal emulator.
In Unicode, the hexadecimal code number is 0x04. It can be referred to as control-D, ^D in the caret notation.
Source: From Federal Standard 1037C