The communication is based on the network virtual terminal (NVT). Its goal is to map a character terminal so neither the "server" nor "user" hosts need to keep information about the characteristics of each other's terminals and terminal handling conventions. NVT uses 7 bit code ASCII characters as the display device. An end of line is transmitted as a CRLF (carriage return followed by a line feed). NVT ASCII is used by many other protocols as well.
NVT defines three mandatory control codes which must be understood by the participants: NULL, CR (Carriage Return), which moves the printer to the left margin of the current line and LF (Line Feed), which moves the printer to the next line keeping the current horizontal position.
NVT also contains some optional commands which are useful. These are the following:
BELL is an audible or visual sign.
BS (Back Space) moves the printer back one position and deletes a character.
HT (Horizontal Tab) moves the printer to the next horizontal tabular stop.
VT Vertical Tab moves the printer to the next vertical tabular stop.
FF (Form Feed) moves the printer to the top of the next page.
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