ASCII format for network interchange
RFC 20

Document Type RFC - Internet Standard (October 1969; Errata)
Last updated 2015-01-28
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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.

Cert                                                            [Page 1]
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 |
+----------------------+-----------------------------------------------+

Cert                                                            [Page 2]
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
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