End of Text

The End of Text character has multiple uses, it's main use was as a transmission control character, it is the fourth Unicode character being U+0003. It is also a C0 or C1 control code. It precedes End of Transmission and succeeds Start of Text

Transmission Control
As a transmission control character, it is used to mark the end of the data of a message. A widely used convention is to make the two characters preceding End of Text a checksum or CRC for error-detection purposes, in other words in a data message it would mark the end of it, normally in data convention the two characters coming after End of Text are made a checksum, a checksum is a small-sized block of data derived from another block of digital data for the purpose of detecting errors that may have been introduced during its transmission or storage. It may also be turned into a CRC, standing for a Cyclic redundancy check, in which is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data, the reason for such is because characters after End of Text can have errors or lose of data, in order to make sure there isn't such the characters get converted to such for error-detection.

Message Transmission
In message transmission (When transmitting messages) delimits the end of the main text of a message, example: This sentence sent transmitted could be STXThis_SentenceETX Might be followed by "post-text information" (i.e. a structured footer) defined by an applicable protocol or by any additional texts, followed by EOT. In keyboard input, often used as a "break" character (Ctrl-C) to interrupt or terminate a program or process.

Computing
It is used to inform the receiving computer that the end of a record has been reached. This may or may not be an indication that all of the data in a record have been received.

Encodings
You can't search this character (if you can then you wont get results) and in HTML, it renders as %03

Other
Currently Nothing