End-of-transmission character

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In telecommunication, 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 headings.^[1]

An EOT is often used to initiate other functions, such as releasing circuits, disconnecting terminals, or placing receive terminals in a standby condition.^[1] In Unix-like systems, the character is used to signal an end-of-file when typing at a terminal or terminal emulator.^{[citation needed]}

In Unicode, the hexadecimal code number is 0x04. It can be referred to as control-D, ^D in the caret notation.^{[citation needed]}

[edit] Demonstration in Unix-based Operating Systems

The 'End of Transmission' meaning of the control-D character can be shown with the cat program on Unix-based operating systems such as Linux.

Run the 'cat' command with no arguments, so that it accepts its input from your keyboard and prints output to your screen. Type a few characters without pressing Enter, then type control-D to indicate End of Transmission. The characters you have typed to that point are sent to cat, which then writes them to the screen. If you type control-D without typing any characters first, you terminate the input stream and the program ends.