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diff --git a/doc/rfc/rfc20.txt b/doc/rfc/rfc20.txt new file mode 100644 index 0000000..22ab96e --- /dev/null +++ b/doc/rfc/rfc20.txt @@ -0,0 +1,507 @@ + + + + + + +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 + 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". + + + + + + + + + + + + + + + + + + + + + + + + +Cert [Page 3] + +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) + + + + + + +Cert [Page 4] + +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 + 3/13 = Equals + 3/14 > Greater Than + 3/15 ? Question Mark + 4/0 @ Commercial At [3] + 5/11 [ Opening Bracket [3] + 5/12 \ Reverse Slant [3] + 5/13 ] Closing Bracket [3] + 5/14 ^ Circumflex [2,3] + 5/15 _ Underline + 6/0 ` Grave Accent [2,3] (Opening Single Quotation + Mark) + 7/11 { Opening Brace [3] + 7/12 | Vertical Line [3] + 7/13 } Closing Brace [3] + 7/14 ~ Overline [3] (Tilde [2]; General Accent [2]) + + ________ + 2 The use of the symbols in 2/2, 2/7, 2/12, 5/14, /6/0, and 7/14 + as diacritical marks is described in Appendix A, A5.2 + 3 These characters should not be used in international interchange + without determining that there is agreement between sender and + recipient. (See Appendix B4.) + 4 In applications where there is no requirement for the symbol #, + the symbol (Pounds Sterling) may be used in position 2/3. + + + +Cert [Page 5] + +RFC 20 ASCII format for Network Interchange October 1969 + + +5. Definitions + +5.1 General + + (CC) Communication Control: A functional character intended to + control or facilitate transmission of information over communication + networks. + (FE) Format Effector: A functional character which controls the + layout or positioning of information in printing or display devices. + (IS) Information Separator: A character which is used to separate + and qualify information in a logical sense. There is a group of four + such characters, which are to be used in a hierarchical order. + +5.2 Control Characters + + 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.) + + + +Cert [Page 6] + +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. + + + +Cert [Page 7] + +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.) + + SUB (Substitute): A character that may be substituted for a + character which is determined to be invalid or in error. + ESC (Escape): A control character intended to provide code + extension (supplementary characters) in general information + interchange. The Escape character itself is a prefix affecting the + interpretation of a limited number of contiguously following + characters. + FS (File Separator), GS (Group Separator), RS (Record Separator), + and US (Unit Separator): These information separators may be used + within data in optional fashion, except that their hierarchical + relationship shall be: FS is the most inclusive, then GS, then RS, + and US is least inclusive. (The content and length of a File, Group, + Record, or Unit are not specified.) + DEL (Delete): This character is used primarily to "erase" or + "obliterate" erroneous or unwanted characters in perforated tape. + (In the strict sense, DEL is not a control character.) + +5.3 Graphic Characters + + SP (Space): A normally non-printing graphic character used to + separate words. It is also a format effector which controls the + movement of the printing position, one printing position forward. + (Applicable also to display devices.) + +6. General Considerations + + 6.1 This standard does not define the means by which the coded set is + to be recorded in any physical medium, nor does it include any + redundancy or define techniques for error control. Further, this + standard does not define data communication character structure, data + communication formats, code extension techniques, or graphic + representation of control characters. + + 6.2 Deviations from the standard may create serious difficulties in + information interchange and should be used only with full cognizance + of the parties involved. + + 6.3 The relative sequence of any two characters, when used as a basis + for collation, is defined by their binary values. + + + + + + + + + +Cert [Page 8] + +RFC 20 ASCII format for Network Interchange October 1969 + + + 6.4 No specific meaning is prescribed for any of the graphics in the + code table except that which is understood by the users. + Furthermore, this standard does not specify a type style for the + printing or display of the various graphic characters. In specific + applications, it may be desirable to employ distinctive styling of + individual graphics to facilitate their use for specific purposes as, + for example, to stylize the graphics in code positions 2/1 and 5/15 + into those frequently associated with logical OR (|) and logical NOT + (252), respectively. + + 6.5 The appendixes to this standard contain additional information on + the design and use of this code. + + + + [ This RFC was put into machine readable form for entry ] + [ into the online RFC archives by Robbie Bennet 9/99] + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Cert [Page 9] + |