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
