VT100.net VT330/VT340 Programmer Reference Manual

Glossary

2-plane bitmap

Graphics page memory for the VT330. In a 2-plane bitmap, each pixel is represented by a 2-bit code. A 2-bit code has four possible values, so the VT330 can display up to four different shades of gray at a time.

4-plane bitmap

Graphics page memory for the VT340. In a 4-plane bitmap, each pixel is represented by a 4-bit code. A 4-bit code has 16 possible values, so the VT340 can display up to 16 different colors or shades at a time.

Absolute location

An unsigned coordinate pair that specifies a location based on the screen origin. For example, [X,Y].

Active position

The current cursor location. Usually, the point that was last moved to or drawn to.

Background intensity

The color or shade of the background on the screen.

Bounded position stack

An option to the ReGIS vector or position command that lets you save the last active position by pushing it onto a stack. You can return the active position to the last saved position by popping the saved position off the stack.

Closed curve sequence

A series of locations the terminal uses to interpolate a curve whose endpoints meet.

Color map

In the VT330, the four output map locations used to store a monochrome intensity value.

In the VT340, the 16 output map locations used to store intensity values. Each location has a monochrome and a color intensity value.

Command key letter

A single letter that identifies the beginning of a ReGIS command. For example, P identifies a position command.

Complement writing

A ReGIS writing style that lets you draw over an image, using the "opposite" shade or color. Complement writing ignores the current foreground intensity, and affects only those areas defined by 1 bits (foreground) in the bit pattern memory.

Coordinate pair

Two values [X,Y] that define a specific location on the screen. The X value defines a location parallel to the horizontal axis. The Y value defines a location parallel to the vertical axis.

Curve interpolation

The action the terminal takes to complete a curve, based on a series of coordinates you specify.

Default

A standard value used by the terminal when the user or program does not specify a value.

Display addressing

The limits of the screen area used for drawing graphics. The terminal uses screen coordinates to address (draw or move to) a point on the screen. The default limits for the VT300 are the coordinates [0,0] and [799,479].

Display cell

The size of the screen area used to display each character. The same display cell is used for all characters.

Erase writing

A ReGIS writing style that lets you write over an existing image by using the background color.

Foreground intensity

The color or shade of the foreground on the screen. The terminal uses this color/shade to draw images when you use the overlay or replace writing style in ReGIS.

Graphics cursor

An indicator that represents the active position on the screen when you use ReGIS. There are two types of graphics cursor, an input cursor and an output cursor. You can use the default cursor characters or select your own.

Gray scale

In the VT330, the four levels of intensity used for drawing, ranging from white to black.

In the VT340, the 16 levels of intensity used for drawing, ranging from white to black.

HLS color system

A color coordinate system for specifying colors, based on their hue, lightness, and saturation. See RGB color system.

Input cursor

A graphics cursor that appears when the terminal is in ReGIS graphics input mode. The default input cursor is a crosshair.

Line pattern

An 8-bit pattern that ReGIS uses to draw lines. You can use a standard pattern or select your own.

Macrograph

A stored string of ReGIS commands or command segments. You use a single letter to name each macrograph. You use macrographs to store text and commands that you use repeatedly.

Mask specifier

One or more characters you can use to define a new graphics cursor style. The mask specifier can be a loaded, or built-in character.

Mnemonic

An abbreviation or acronym for a command or a control character.

Monochrome map

The four output map locations that the VT330 uses to select the intensity of the display. Each location stores a different intensity, from white to black.

Offset

A distance from a given location.

Open curve sequence

A series of points that the terminal uses to interpolate a curve whose endpoints do not necessarily meet.

Output cursor

A graphics cursor that appears when the terminal is waiting for ReGIS input from the host system. The output cursor indicates the current drawing position. The default output cursor is a diamond.

Overlay writing

A ReGIS writing style that lets you draw only in the foreground, not the background.

Pixel

A picture element. The smallest displayable unit on the screen.

Pixel vector (PV) system

In ReGIS, a method for selecting the direction to draw or move incrementally on the screen. You can select from eight different directions, at 45 degree increments.

Position stack

A set of coordinate positions that ReGIS uses in sequence. You use position stacks to move the cursor to several positions in a single vector or position command. There are two types of position stacks, bounded and unbounded.

PV multiplication factor

An integer used to select the number of pixels to move for each PV value specified. ReGIS uses the PV multiplication factor for all PV values you enter. You can change the PV multiplication factor.

Relative location

A point on the screen measured from a specified location, rather than from the screen origin.

ReGIS

Digital's graphics instruction set that lets you build images from standard geometric forms, such as lines, curves, and circles.

Replace writing

A ReGIS writing style that lets you draw in both the foreground and the background.

RGB color system

A coordinate system for specifying colors, based on the three primary colors red, green, and blue. See HLS color system.

Screen origin

The first ReGIS coordinate at the upper-left corner of the screen. This coordinate is [0,0].

Shading reference line

A horizontal or vertical line that ReGIS uses when shading images. Shading occurs between the shading reference line and the point being drawn or moved to.

Unbounded position stack

An option to the ReGIS vector or position command that lets you save a nonexistent position by pushing it onto a stack. The active position does not move when the saved dummy position is popped off the stack. See bounded position stack.

Unit cell

The maximum size of each display character within the display cell.

Vector

A directed line. You use the ReGIS vector command to draw lines.

Vertex

One of the points defining a polygon.