VT100 User Guide

Chapter 5

Contents

Appendix B

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Appendix A
ANSI Definitions and Notation

ANSI Definitions

Active position

The character position on the visual display that is to display the graphic symbol representing the next graphic character.

ANSI mode

A VT100 mode in which it recognizes and responds only to escape sequences whose syntax and semantics are in accordance with ANSI specifications.

Character position

That portion of a visual display which is displaying or is capable of displaying a graphic symbol.

Control

A control character, an escape sequence, or a control sequence that performs a control function.

Control character

A character whose occurrence in a particular context initiates, modifies, or stops a control function.

Control function

An action that affects the recording, processing, transmission, or interpretation of data.

Control sequence

A sequence of characters that is used for control purposes to perform a control function, that begins with the control sequence introducer (CSI) control, and that may contain a parameter string.

Control sequence introducer (CSI)

An escape sequence that provides supplementary controls and that is itself a prefix affecting the interpretation of a limited number of contiguous characters.

Control string

A string of characters that is used to perform a control function and that is delimited by an opening and closing delimiter control.

Cursor

A visual representation of the active position which is either a blinking reverse-video or blinking underline.

Cursor control

An editor function that moves the active position.

Default

A function-dependent value that is assumed when no explicit value, or a value of 0, is specified.

Display

The current active area of the screen, i.e., the area inside the scrolling region, or the entire screen, depending on the origin mode.

Editor function

A control that affects the layout or positioning of previously entered or received information in a printing or cathode ray tube display and that is intended to be interpreted and executed without remaining in the data stream. (See format effector).

Escape character (ESC)

A control character that provides supplementary characters (code extension) and that is itself a prefix affecting the interpretation of a limited number of contiguous characters.

Escape sequence

A sequence of characters that is used for control purposes to perform a control function and whose first character is the escape (ESC) control character.

Final character

A character whose bit combination terminates an escape or control sequence designated by F.

Format effector

A control that affects the layout or positioning of information on the screen and that may remain in the data stream subsequent to interpretation and processing. (See editor function).

Graphic character

A character, other than a control character, that has a visual representation normally handwritten, printed, or displayed.

Home

The character position at the origin. [See origin mode (DECOM).]

Intermediate character

A character whose bit combination precedes a final character in an escape or control sequence.

Numeric parameter

A string of bit combinations that represents a number, designated by Pn.

Parameter

1. A string of one or more characters that represent a single value:
2. The value so represented.

Parameter string

A string of characters that represent one or more parameter values.

Selective parameter

A string of bit combinations that selects a subfunction from a specified list of subfunctions, designated by Ps. In general, a control sequence with more than one selective parameter causes the same effect as several control sequences, each with one selective parameter, e.g., CSI Psa; Psb; Psc F is identical to CSI Psa F CSI Psb F CSI Psc F.

VT52 mode

A VT100 mode in which it recognizes and responds only to escape sequences which DEC VT52 type terminals use.

Notation

I

An intermediate character in an escape sequence or a control sequence, where I is from 40₈ to 57₈ inclusive.

F

A Final character in:

1. An escape sequence, where F is from 60₈ to 176₈ inclusive.
2. A control sequence, where F is from 100₈ to 176₈ inclusive.

   Pn

   A numeric parameter in a control sequence, where Pn is a string of zero or more characters from 60₈ to 71₈ inclusive.

   Ps

   A variable number of selective parameters in a control sequence, with each selective parameter separated from the other by 73₈. Ps is a string of zero or more characters from 60₈ to 71₈ inclusive and 73₈.

Example: The format of an escape sequence as defined in American National Standard X3.41-1974 and used in the VT100 is:

ESC I ... I F

Where:

1. ESC is the introducer control character (33₈) that is named escape.
2. I ... I are the intermediate bit combinations that may or may not be present. I characters are bit combination 40₈ to 57₈ inclusive in both 7- and 8-bit environments.
3. F is the final character. F characters are bit combinations 60₈ to 176₈ inclusive in escape sequences in both 7- and 8-bit environments.
4. The occurrence of characters in the inclusive ranges of 0₈ to 37₈ within an escape or control sequence, is technically an error condition whose recovery is to execute immediately the function specified by the character and then continue with the escape sequence execution. The exceptions are: If the character ESC occurs, the current escape sequence is aborted, and a new one commences, beginning with the ESC just received. If the character CAN (30₈) or the character SUB (32₈) occurs, the current escape sequence is aborted.