NUL (Null): The all-zeros character which may serve to accomplish
   time fill and media fill.
      SOH (Start of Heading): A communication control character used at
   the beginning of a sequence of characters which constitute a
   machine-sensible address or routing information.  Such a sequence is
   referred to as the "heading."  An STX character has the effect of
   terminating a heading.
      STX (Start of Text): A communication control character which
   precedes a sequence of characters that is to be treated as an entity
   and entirely transmitted through to the ultimate destination.  Such a
   sequence is referred to as "text."  STX may be used to terminate a
   sequence of characters started by SOH.
      ETX (End of Text): A communication control character used to
   terminate a sequence of characters started with STX and transmitted
   as an entity.
      EOT (End of Transmission): A communication control character used
   to indicate the conclusion of a transmission, which may have
   contained one or more texts and any associated headings.
      ENQ (Enquiry): A communication control character used in data
   communication systems as a request for a response from a remote
   station.  It may be used as a "Who Are You" (WRU) to obtain
   identification, or may be used to obtain station status, or both.
      ACK (Acknowledge): A communication control character transmitted
   by a receiver as an affirmative response to a sender.
      BEL (Bell): A character for use when there is a need to call for
   human attention.  It may control alarm or attention devices.
      BS (Backspace): A format effector which controls the movement of
   the printing position one printing space backward on the same
   printing line.  (Applicable also to display devices.)
      HT (Horizontal Tabulation): A format effector which controls the
   movement of the printing position to the next in a series of
   predetermined positions along the printing line.  (Applicable also to
   display devices and the skip function on punched cards.)




 
RFC 20            ASCII format for Network Interchange      October 1969


      LF (Line Feed): A format effector which controls the movement of
   the printing position to the next printing line.  (Applicable also to
   display devices.) Where appropriate, this character may have the
   meaning "New Line" (NL), a format effector which controls the
   movement of the printing point to the first printing position on the
   next printing line.  Use of this convention requires agreement
   between sender and recipient of data.
      VT (Vertical Tabulation): A format effector which controls the
   movement of the printing position to the next in a series of
   predetermined printing lines.  (Applicable also to display devices.)
      FF (Form Feed): A format effector which controls the movement of
   the printing position to the first pre-determined printing line on
   the next form or page.  (Applicable also to display devices.)
      CR (Carriage Return): A format effector which controls the
   movement of the printing position to the first printing position on
   the same printing line.  (Applicable also to display devices.)
      SO (Shift Out): A control character indicating that the code
   combinations which follow shall be interpreted as outside of the
   character set of the standard code table until a Shift In character
   is reached.
      SI (Shift In): A control character indicating that the code
   combinations which follow shall be interpreted according to the
   standard code table.
      DLE (Data Link Escape): A communication control character which
   will change the meaning of a limited number of contiguously following
   characters.  It is used exclusively to provide supplementary controls
   in data communication networks.
      DC1, DC2, DC3, DC4 (Device Controls): Characters for the control
   of ancillary devices associated with data processing or
   telecommunication systems, more especially switching devices "on" or
   "off."  (If a single "stop" control is required to interrupt or turn
   off ancillary devices, DC4 is the preferred assignment.)
      NAK (Negative Acknowledge): A communication control character
   transmitted by a receiver as a negative response to the sender.
      SYN (Synchronous Idle): A communication control character used by
   a synchronous transmission system in the absence of any other
   character to provide a signal from which synchronism may be achieved
   or retained.
      ETB (End of Transmission Block): A communication control character
   used to indicate the end of a block of data for communication
   purposes.  ETB is used for blocking data where the block structure is
   not necessarily related to the processing format.
      CAN (Cancel): A control character used to indicate that the data
   with which it is sent is in error or is to be disregarded.
      EM (End of Medium): A control character associated with the sent
   data which may be used to identify the physical end of the medium, or
   the end of the used, or wanted, portion of information recorded on a
   medium.




 
RFC 20            ASCII format for Network Interchange      October 1969


(The position of this character does not necessarily correspond to the
   physical end of the medium.)