RFC 318 (rfc318) - Page 2 of 16
Telnet Protocols
Alternative Format: Original Text Document
RFC 318 Telnet Protocol April 1972
I. DEFINITION OF THE NETWORK VIRTUAL TERMINAL
The Network Virtual Terminal (NVT) is a bi-directional character
device. The characters are represented by 8 bit codes. The NVT has
no timing characteristics. The character codes 0 through 127 are the
USASCII codes. (Note all code values are given in decimal.) The
codes 128 through 255 are used for special control signals. The NVT
is described as having a printer and a keyboard. The printer
responds to incoming data and the keyboard produces outgoing data.
The Printer
The NVT printer has an unspecified carriage width (common values are
40, 72, 80, 120, 128, 132). The printer can produce representations
of all 95 USASCII graphics (codes 32 through 126). Of the 33 USASCII
control codes (0 through 31 and 127) the following 8 have specific
meaning to the NVT printer.
NAME CODE MEANING
NULL (NUL) 0 A no operation.
BELL (BEL) 7 Produces an audible or visible signal.
Back Space (BS) 8 Backspaces the printer one character
position.
Horizontal Tab (HT) 9 Moves the printer to next horizontal
tab stop.
Line Feed (LF) 10 Moves the printer to next line (keeping
the same horizontal position).
Vertical Tab (VT) 11 Moves the printer to the next vertical
tab stop.
Form Feed (FF) 12 Moves the printer to the top of the
next page.
Carriage Return (CR) 13 Moves the printer to the left margin
of the current line.
The remaining USASCII codes (1 through 6, 14 through 31, and 127) do
not cause the NVT printer to take any action.
Postel