rfc20.txt

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Network Working Group                                          Vint Cerf
Request for Comments: 20                                            UCLA
                                                        October 16, 1969


                  ASCII format for Network Interchange

   For concreteness, we suggest the use of standard 7-bit ASCII embedded
   in an 8 bit byte whose high order bit is always 0.  This leads to the
   standard code given on the attached page, copies from USAS X3, 4-
   1968.  This code will be used over HOST-HOST primary connections.
   Break characters will be defined by the receiving remote host, e.g.
   SRI uses "." (ASCII X'2E' or 2/14) as the end-of-line character,
   where as UCLA uses X'OD' or 0/13 (carriage return).




USA Standard Code for Information Interchange

1. Scope

   This coded character set is to be used for the general interchange of
   information among information processing systems, communication
   systems, and associated equipment.


























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RFC 20            ASCII format for Network Interchange      October 1969


2. Standard Code

|----------------------------------------------------------------------|
  B  \ b7 ------------>| 0   | 0   | 0   | 0   | 1   | 1   | 1   | 1   |
   I  \  b6 ---------->| 0   | 0   | 1   | 1   | 0   | 0   | 1   | 1   |
    T  \   b5 -------->| 0   | 1   | 0   | 1   | 0   | 1   | 0   | 1   |
     S                 |-----------------------------------------------|
               COLUMN->| 0   | 1   | 2   | 3   | 4   | 5   | 6   | 7   |
|b4 |b3 |b2 |b1 | ROW  |     |     |     |     |     |     |     |     |
+----------------------+-----------------------------------------------+
| 0 | 0 | 0 | 0 | 0    | NUL | DLE | SP  | 0   | @   | P   |   ` |   p |
|---|---|---|---|------|-----|-----|-----|-----|-----|-----|-----|-----|
| 0 | 0 | 0 | 1 | 1    | SOH | DC1 | !   | 1   | A   | Q   |   a |   q |
|---|---|---|---|------|-----|-----|-----|-----|-----|-----|-----|-----|
| 0 | 0 | 1 | 0 | 2    | STX | DC2 | "   | 2   | B   | R   |   b |   r |
|---|---|---|---|------|-----|-----|-----|-----|-----|-----|-----|-----|
| 0 | 0 | 1 | 1 | 3    | ETX | DC3 | #   | 3   | C   | S   |   c |   s |
|---|---|---|---|------|-----|-----|-----|-----|-----|-----|-----|-----|
| 0 | 1 | 0 | 0 | 4    | EOT | DC4 | $   | 4   | D   | T   |  d  |   t |
|---|---|---|---|------|-----|-----|-----|-----|-----|-----|-----|-----|
| 0 | 1 | 0 | 1 | 5    | ENQ | NAK | %   | 5   | E   | U   |  e  |   u |
|---|---|---|---|------|-----|-----|-----|-----|-----|-----|-----|-----|
| 0 | 1 | 1 | 0 | 6    | ACK | SYN | &   | 6   | F   | V   |  f  |   v |
|---|---|---|---|------|-----|-----|-----|-----|-----|-----|-----|-----|
| 0 | 1 | 1 | 1 | 7    | BEL | ETB | '   | 7   | G   | W   |  g  |   w |
|---|---|---|---|------|-----|-----|-----|-----|-----|-----|-----|-----|
| 1 | 0 | 0 | 0 | 8    | BS  | CAN | (   | 8   | H   | X   |  h  |   x |
|---|---|---|---|------|-----|-----|-----|-----|-----|-----|-----|-----|
| 1 | 0 | 0 | 1 | 9    | HT  | EM  | )   | 9   | I   | Y   |  i  |   y |
|---|---|---|---|------|-----|-----|-----|-----|-----|-----|-----|-----|
| 1 | 0 | 1 | 0 | 10   | LF  | SUB | *   | :   | J   | Z   |  j  |   z |
|---|---|---|---|------|-----|-----|-----|-----|-----|-----|-----|-----|
| 1 | 0 | 1 | 1 | 11   | VT  | ESC | +   |  ;  | K   | [   |  k  |   { |
|---|---|---|---|------|-----|-----|-----|-----|-----|-----|-----|-----|
| 1 | 1 | 0 | 0 | 12   | FF  | FS  | ,   | <   | L   | \   |  l  |   | |
|---|---|---|---|------|-----|-----|-----|-----|-----|-----|-----|-----|
| 1 | 1 | 0 | 1 | 13   | CR  | GS  | -   | =   | M   | ]   |  m  |   } |
|---|---|---|---|------|-----|-----|-----|-----|-----|-----|-----|-----|
| 1 | 1 | 1 | 0 | 14   | SO  | RS  | .   | >   | N   | ^   |  n  |   ~ |
|---|---|---|---|------|-----|-----|-----|-----|-----|-----|-----|-----|
| 1 | 1 | 1 | 1 | 15   | SI  | US  | /   | ?   | O   | _   |  o  | DEL |
+----------------------+-----------------------------------------------+









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RFC 20            ASCII format for Network Interchange      October 1969


3. Character Representation and Code Identification

   The standard 7-bit character representation, with b7 the high-order
   bit and b1 the low-order bit, is shown below:

   EXAMPLE: The bit representation for the character "K," positioned in
   column 4, row 11, is

   b7 b6 b5 b4 b3 b2 b1
   1  0  0  1  0  1  1


   The code table position for the character "K" may also be represented
   by the notation "column 4, row 11" or alternatively as "4/11."  The
   decimal equivalent of the binary number formed by bits b7, b6, and
   b5, collectively, forms the column number, and the decimal equivalent
   of the binary number formed by bits b4, b3, b2, and b1, collectively,
   forms the row number.

   The standard code may be identified by the use of the notation ASCII
   or USASCII.

   The notation ASCII (pronounced as'-key) or USASCII (pronounced you-
   sas'-key) should ordinarily be taken to mean the code prescribed by
   the latest issue of the standard.  To explicitly designate a
   particular (perhaps prior) issue, the last two digits of the year of
   issue may be appended, as, "ASCII 63" or "USASCII 63".
























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RFC 20            ASCII format for Network Interchange      October 1969


4. Legend

4.1 Control Characters

   NUL Null                                DLE Data Link Escape (CC)

   SOH Start of Heading (CC)               DC1 Device Control 1

   STX Start of Text (CC)                  DC2 Device Control 2

   ETX End of Text (CC)                    DC3 Device Control 3

   EOT End of Transmission (CC)            DC4 Device Control 4 (Stop)

   ENQ Enquiry (CC)                        NAK Negative Acknowledge (CC)

   ACK Acknowledge (CC)                    SYN Synchronous Idle (CC)

   BEL Bell (audible or                    ETB End of Transmission
       attention signal)                       Block (CC)

   BS Backspace (FE)                       CAN Cancel

   HT Horizontal Tabulation                EM End of Medium
      (punched card skip) (FE)

   LF Line Feed (FE)                       SUB Substitute

   VT Vertical Tabulation (FE)             ESC Escape

   FF Form Feed (FE)                       FS File Separator IS)

   CR Carriage Return (FE)                 GS Group Separator (IS)

   SO Shift Out                            RS Record Separator (IS)

   SI Shift In                             US Unit Separator (IS)

                                           DEL Delete [1]

   ________
   NOTE: (CC) Communication Control
         (FE) Format Effector
         (IS) Information Separator
   [1] In the strict sense, DEL is not a control character.  (See 5.2)






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RFC 20            ASCII format for Network Interchange      October 1969


4.2 Graphic Characters

   Column/Row  Symbol      Name

   2/0         SP          Space (Normally Non-Printing)
   2/1         !           Exclamation Point
   2/2         "           Quotation Marks (Diaeresis [2])
   2/3         #           Number Sign [3,4]
   2/4         $           Dollar Sign
   2/5         %           Percent
   2/6         &           Ampersand
   2/7         '           Apostrophe (Closing Single Quotation Mark
                           Acute Accent [2])
   2/8         (           Opening Parenthesis
   2/9         )           Closing Parenthesis
   2/10        *           Asterisk
   2/11        +           Plus
   2/12        ,           Comma (Cedilla [2])
   2/13        -           Hyphen (Minus)
   2/14        .           Period (Decimal Point)
   2/15        /           Slant
   3/10        :           Colon
   3/11        ;           Semicolon
   3/12        <           Less Than