Glossary

Definitions of common terms associated with AutoCAD LT

A

absolute coordinates

Coordinate values measured from a coordinate system's origin point. See also origin, relative coordinates, user coordinate system (UCS), world coordinates, and World Coordinate System (WCS).

adaptive sampling

A method to accelerate the anti-aliasing process within the bounds of the sample matrix size. See also anti-aliasing.

ADI

For Autodesk Device Interface. An interface specification for developing device drivers that are required for peripherals to work with AutoCAD LT and other Autodesk products.

affine calibration

A tablet calibration method that provides an arbitrary linear transformation in two-dimensional space. Affine calibration requires three calibration points to allow a tablet transformation that combines translation, independent X and Y scaling, rotation, and some skewing. Use affine calibration if a drawing has been stretched differently in the horizontal or vertical direction. (Associated command: TABLET)

alias

A shortcut for an AutoCAD LT command. For example, CP is an alias for COPY, and Z is an alias for ZOOM. You define aliases in the aclt.pgp file.

aliasing

The effect of discrete picture elements, or pixels, aligned as a straight or curved edge on fixed grid appearing to be jagged or stepped. See also anti-aliasing.

aligned dimension

A dimension that measures the distance between two points at any angle. The dimension line is parallel to the line connecting the dimension's definition points. (Associated command: DIMALIGNED)

angular dimension

A dimension that measures angles or arc segments and consists of text, extension lines, and leaders. (Associated command: DIMANGULAR)

angular unit

The unit of measurement for an angle. Angular units can be measured in decimal degrees, degrees/minutes/seconds, grads, and radians.

annotations

Text, dimensions, tolerances, symbols, or notes.

anonymous block

An unnamed block that supports associative dimensions.

ANSI

For American National Standards Institute. Coordinator of voluntary standards development for both private and public sectors in the United States. Standards pertain to programming languages, Electronic Data Interchange (EDI), telecommunications, and the physical properties of diskettes, cartridges, and magnetic tapes.

anti-aliasing

A method that reduces aliasing by shading the pixels adjacent to the main pixels that define a line or boundary.

approximation points

Point locations that a B-spline must pass near, within a fit tolerance. See also fit points and interpolation points.

array

1. Multiple copies of selected AutoCAD LT objects in a rectangular or polar (radial) pattern. (Associated command: ARRAY) 2. A collection of data items, each identified by a subscript or key, arranged so a computer can examine the collection and retrieve data with the key.

arrowhead

A terminator, such as an arrowhead, slash, or dot, at the end of a dimension line showing where a dimension begins and ends.

ASCII

For American Standard Code for Information Interchange. A common numeric code used in computer data communications. The code assigns meaning to 128 numbers, using seven bits per character with the eighth bit used for parity checking. Nonstandard versions of ASCII assign meaning to 255 numbers.

aspect ratio

Ratio of display width to height.

associative dimension

A dimension that adapts as the associated geometry is modified.

associative hatching

Hatching that conforms to its bounding objects such that modifying the bounding objects automatically adjusts the hatch. (Associated command: BHATCH)

attribute definition

An AutoCAD LT object that is included in a block definition to store alphanumeric data. Attribute values can be predefined or specified when the block is inserted. Attribute data can be extracted from a drawing and inserted into external files. (Associated commands: DDATTDEF, ATTDEF)

attribute extraction file

An ASCII text file to which extracted attribute data is written. The contents and format are determined by the attribute extraction template file.

attribute extraction template file

An ASCII text file that determines which attributes are extracted and how they are formatted when written to an attribute extraction file.

attribute prompt

The text string displayed when you insert a block with an attribute whose value is undefined. See also attribute definition, attribute tag, and attribute value.

attribute tag

A text string associated with an attribute that identifies a particular attribute during extraction from the drawing database. attribute definition, attribute prompt, and attribute value. See also attribute definition, attribute prompt, and attribute value.

attribute value

The alphanumeric information associated with an attribute tag. See also attribute definition, attribute prompt, and attribute tag.

AutoCAD LT library search path

The order in which AutoCAD LT looks for a support file: current directory, drawing directory, directory specified in the support path, and directory containing the AutoCAD executable file, aclt.exe.

axis tripod

Icon with X, Y, and Z coordinates that is used to visualize the viewpoint (view direction) of a drawing without displaying the drawing. (Associated command: VPOINT)

B

baseline

An imaginary line on which text characters appear to rest. Individual characters can have descenders that drop below the baseline.

baseline dimension

Multiple dimensions measured from the same baseline. Also called parallel dimensions.

base point

1. In the context of editing grips, the grip that changes to a solid color when selected to specify the focus of the subsequent editing operation. 2. A point for relative distance and angle when copying, moving, and rotating objects. 3. The insertion base point of the current drawing. (Associated command: BASE) 4. The insertion base point for a block definition. (Associated command: BLOCK)

Bezier curve

A polynomial curve defined by a set of control points, representing an equation of an order one less than the number of points being considered. A Bezier curve is a special case of a B-spline curve.

bitmap

The digital representation of an image having bits referenced to pixels. In color graphics, a different value represents each red, green, and blue component of a pixel.

blip marks

Temporary screen markers displayed in the AutoCAD LT graphics area when you specify a point or select objects. (Associated command: BLIPMODE)

block

A generic term for one or more AutoCAD LT objects that are combined to create a single object. Commonly used for either block definition or block reference. See block definition and block reference. (Associated command: BLOCK)

block definition

The name, base point, and set of objects that are combined and stored in the symbol table of a drawing. See block. See also block reference. (Associated command: BLOCK)

block reference

A compound object that is inserted in a drawing and displays the data stored in a block definition. Also called instance. See block. See also block definition. (Associated command: INSERT)

block table

The nongraphic data area of a drawing file that stores block definitions. See also symbol table.

B-spline curve

A blended piecewise polynomial curve passing near a given set of control points. (Associated command: SPLINE)

button menu

The menu for a pointing device with multiple buttons. Each button on the pointing device (except the pick button) can be defined in the AutoCAD LT menu file aclt.mnu in the BUTTONSn and AUXn sections.

BYBLOCK

A special object property used to specify that the object inherits the color or linetype of any block containing it. See also BYLAYER.

BYLAYER

A special object property used to specify that the object inherits the color or linetype associated with its layer. See also BYBLOCK.

C

circular external reference

An externally referenced drawing (xref) that references itself directly or indirectly. AutoCAD LT ignores the xref that creates the circular condition.

clipping planes

The boundaries that define or clip the field of view. (Associated command: DVIEW)

command line

A text area reserved for keyboard input, prompts, and messages.

construction plane

A plane on which planar geometry is constructed. The XY plane of the current UCS represents the construction plane. See also elevation and user coordinate system.

continued dimension

A type of linear dimension that uses the second extension line origin of a selected dimension as its first extension line origin, breaking one long dimension into shorter segments that add up to the total measurement. Also called chain dimension. (Associated command: DIMCONTINUE)

control frame

A series of point locations used as a mechanism to control the shape of a B-spline. These points are connected by a series of line segments for visual clarity and to distinguish the control frame from fit points. The SPLFRAME system variable must be turned on to display control frames.

coordinate filters

Functions that extract individual X, Y, and Z coordinate values from different points to create a new, composite point. Also called X,Y,Z point filters.

CPolygon

A multisided area specified to select objects fully or partially within its borders. See also crossing window and WPolygon.

crosshairs

A type of cursor consisting of two lines that intersect. Also called graphics cursor.

crossing window

A rectangular area drawn to select objects fully or partly within its borders. See also CPolygon.

cursor

A pointer on a video display screen that can be moved around to place textual or graphical information. Also called graphics cursor. See also crosshairs.

cursor menu

The menu that is displayed in the graphics area at the cursor location when you hold down SHIFT and press the Enter button on a pointing device. The cursor menu is defined in the POP0 section of aclt.mnu.

D

default

A predefined value for a program input or parameter. Default values and options for AutoCAD LT commands are denoted by angle braces <>.

definition points

Points for creating an associative dimension. AutoCAD LT refers to the points to modify the appearance and value of an associative dimension when the associated object is modified. Also called defpoints and stored on the special layer DEFPOINTS.

dependent symbols

Symbol table definitions that are brought into a drawing by an external reference. See also symbol table.

DIESEL

For Direct Interpretively Evaluated String Expression Language. A macro language for altering the AutoCAD LT status line with the MODEMACRO system variable and for customizing menu items.

dimension line arc

An arc (usually with arrows at each end) spanning the angle formed by the extension lines of an angle being measured. The dimension text near this arc sometimes divides it into two arcs. See also angular dimension.

dimension style

A named group of dimension settings that determines the appearance of the dimension and simplifies setting dimension system variables. (Associated command: DDIM)

dimension text

The measurement value of dimensioned objects.

dimension variables

A set of numeric values, text strings, and settings that control AutoCAD LT dimensioning features. (Associated command: DDIM)

direct distance entry

A method to specify a second point by first moving the cursor to indicate direction and then entering a distance.

dithering

Combining color dots to give the impression of displaying more colors than are actually available.

drawing extents

The smallest rectangle that contains all objects in a drawing, positioned on the screen to display the largest possible view of all objects. (Associated command: ZOOM)

drawing limits

The user-defined rectangular boundary of the drawing area covered by dots when the grid is turned on. Also called grid limits. (Associated command: LIMITS)

DWF

For drawing Web format. A highly compressed file format that is created from a DWG file. DWF files are easy to publish and view on the Web.

DWG

Standard file format for saving vector graphics from within AutoCAD LT.

DXF

For drawing interchange format. An ASCII or binary file format of an AutoCAD LT drawing file for exporting AutoCAD LT drawings to other applications or for importing drawings from other applications.

E

elevation

The default Z value above or below the XY plane of the current user coordinate system, which is used for entering coordinates and digitizing locations. (Associated command: ELEV)

embed

To use object linking and embedding (OLE) information from a source document in a destination document. An embedded object is a copy of the information from a source document that is placed in the destination document and has no link to the source document. See also link.

explode

To disassemble a complex object, such as a block, solid, or polyline, into simpler objects. In the case of a block, the block definition is unchanged. The block reference is replaced by the components of the block. See also block, block definition, and block reference. (Associated command: EXPLODE)

external reference (xref)

A drawing file linked (or attached) to another drawing. (Associated command: XREF)

F

feature control frame

Specifies the tolerance that applies to specific features or patterns of features. Feature control frames always contain at least a geometric characteristic symbol to indicate the type of control and a tolerance value to indicate the amount of acceptable variation.

fence

A multisegmented line specified to select objects it passes through.

fill

A solid color covering an area bounded by lines or curves. (Associated command: FILL)

fit points

Locations that a B-spline must pass through exactly or within a fit tolerance. See also interpolation points and approximation points.

fit tolerance

The setting for the maximum distance that a B-spline can pass for each of the fit points that define it.

floating viewports

Rectangular objects that are created in paper space that display views. See also paper space. (Associated command: MVIEW)

font

A character set, comprising letters, numbers, punctuation marks, and symbols, of a distinctive proportion and design.

freeze

A setting that suppresses the display of objects on selected layers. Objects on frozen layers are not displayed, regenerated, or plotted. Freezing layers shortens regenerating time. See also thaw. (Associated command: LAYER)

G

graphics area

The area of the AutoCAD LT screen for creating and editing a drawing.

graphics cursor

See crosshairs and cursor.

graphics window

The graphics area, its surrounding menus, and the command line.

grid

An area on the graphics display covered with regularly spaced dots to aid drawing. The spacing between grid dots is adjustable. Grid dots are not plotted. See also drawing limits. (Associated command: GRID)

grip modes

The editing capabilities activated when grips are displayed on an object: stretching, moving, rotating, scaling, and mirroring.

grips

Small squares that appear on objects you select. After selecting the grip, you edit the object by dragging it with the mouse instead of entering commands.

H

handle

A unique alphanumeric tag for an object in the AutoCAD LT database.

home page

The main navigating screen for a Web site.

I

IGES

For initial graphics exchange specification. An ANSI-standard format for digital representation and exchange of information between CAD/CAM systems.

initial environment

The variables and settings for new drawings as defined by the default template drawing, such as aclt.dwg or acltiso.dwg. See also template drawing.

interpolation points

Defining points that a B-spline passes through. See also approximation points and fit points.

island

An enclosed area within a hatched area.

ISO

For International Standards Organization. The organization that sets international standards in all fields except electrical and electronics. Headquarters are in Geneva, Switzerland.

isometric snap style

An AutoCAD LT drafting option that aligns the cursor with two of three isometric axes and displays grid points, making isometric drawings easier to create.

L

layer

A logical grouping of data that are like transparent acetate overlays on a drawing. You can view layers individually or in combination. (Associated command: LAYER)

linetype

How a line or type of curve is displayed. For example, a continuous line has a different linetype than a dashed line. Also called line font. (Associated command: LINETYPE)

link

To use object linking and embedding (OLE) to reference data in another file. When data is linked, any changes to it in the source document is automatically updated in any destination document. See also embed.

M

mirror

To create a new version of an existing object by reflecting it symmetrically with respect to a prescribed line or plane. (Associated command: MIRROR)

mode

A software setting or operating state.

model

A two- or three-dimensional representation of an object.

model space

One of the two primary spaces in which AutoCAD LT objects reside. Typically, a geometric model is placed in a three-dimensional coordinate space called model space. A final layout of specific views and annotations of this model is placed in paper space. See also paper space. (Associated command: MSPACE)

N

named view

A view saved for restoration later. (Associated command: VIEW)

node

An object snap specification to locate points, dimension definition points, and dimension text origins.

noun-verb selection

Selecting an object first and then performing an operation on it rather than entering a command first and then selecting the object.

NURBS

For nonuniform rational B-spline curve. A B-spline curve or surface defined by a series of weighted control points and one or more knot vectors. See B-spline curve.

O

object

One or more AutoCAD LT graphical elements, such as text, dimensions, lines, circles, or polylines, treated as a single element for creation, manipulation, and modification. Also called entity.

Object Snap modes

Methods for selecting commonly needed points on an object while you create or edit an AutoCAD LT drawing. See also running object snap and object snap override.

object snap override

Turning off or changing a running object snap mode for input of a single point. See also Object Snap modes and running object snap.

OLE

For object linking and embedding. An information-sharing method in which data from a source document can be linked to or embedded in a destination document. Selecting the data in the destination document opens the source application so that the data can be edited. See also embed and link.

origin

The point where coordinate axes intersect. For example, the origin of a Cartesian coordinate system is where the X, Y, and Z axes meet at 0,0,0.

orthogonal

Having perpendicular slopes or tangents at the point of intersection.

Ortho mode

An AutoCAD LT setting that limits pointing device input to horizontal or vertical (relative to the current snap angle and the user coordinate system). See also snap angle and user coordinate system.

P

pan

To shift the view of a drawing without changing magnification. See also zoom. (Associated command: PAN)

paper space

One of two primary spaces in which AutoCAD LT objects reside. Paper space is used for creating a finished layout for printing or plotting, as opposed to doing drafting or design work. Model space is used for creating the drawing. See also model space and viewport. (Associated command: PSPACE)

personalization

Customizing the AutoCAD LT executable file, aclt.exe, during installation by entering the user name, company, and other information.

pick button

The button on a pointing device that is used to select objects or specify points on the screen. For example, on a two-button mouse, it is the left button.

plan view

A view orientation from a point on the positive Z axis toward the origin (0,0,0). (Associated command: PLAN)

point

1. A location in three-dimensional space specified by X, Y, and Z coordinate values. 2. An AutoCAD LT object consisting of a single coordinate location. (Associated command: POINT)

polar array

Objects copied around a specified center point a specified number of times. (Associated command: ARRAY)

polygon window

A multisided area specified to select objects in groups. See also CPolygon, crossing window, and WPolygon.

polyline

An AutoCAD LT object composed of one or more connected line segments or circular arcs treated as a single object. Also called pline. (Associated commands: PLINE, PEDIT)

prompt

A message on the command line that asks for information or requests action such as specifying a point.

R

redraw

To quickly refresh or clean up the current viewport without updating the drawing's database. See also regenerate. (Associated command: REDRAW)

regenerate

To update a drawing's screen display by recomputing the screen coordinates from the database. See also redraw. (Associated command: REGEN)

relative coordinates

Coordinates specified in relation to previous coordinates.

return button

The button on a pointing device used to accept an entry. For example, on a two-button mouse, it is the right button.

RGB

For red, green, and blue. A system of defining colors by specifying percentages of red, green, and blue.

rubber-band line

A line that stretches dynamically on the screen with the movement of the cursor. One endpoint of the line is attached to a point in your drawing, and the other is attached to the moving cursor.

running object snap

Setting an object snap mode so it continues for subsequent selections. See also Object Snap modes and object snap override. (Associated command: OSNAP)

S

script file

A set of AutoCAD LT commands executed sequentially with a single SCRIPT command. Script files are created outside AutoCAD LT using a text editor, saved in text format, and stored in an external file with the extension .scr.

selection set

One or more AutoCAD LT objects specified for processing as a unit.

selection window

A rectangular area drawn in the AutoCAD LT graphics area to select objects in groups. See also CPolygon, crossing window, polygon window, and WPolygon.

slide file

A file that contains a raster image or snapshot of the display on the graphics screen. Slide files work with Autodesk Animator and Animator Pro and have the file extension .sld. (Associated commands: MSLIDE, VSLIDE)

slide library

A collection of slide files organized for convenient retrieval and display. Slide library names have the extension .slb and are created with the slidelib.exe utility.

snap angle

The angle that the snap grid is rotated.

snap grid

The invisible grid that locks the graphics cursor into alignment with the grid points according to the spacing set by SNAP. Snap grid does not necessarily correspond to the visible grid, which is controlled separately by GRID. (Associated command: SNAP)

Snap mode

A mode for locking a pointing device into alignment with an invisible rectangular grid. When Snap mode is on, the screen crosshairs and all input coordinates are snapped to the nearest point on the grid. The snap resolution defines the spacing of this grid. See also Object Snap modes. (Associated command: SNAP)

snap resolution

The spacing between points of the snap grid.

symbol table

A nongraphic AutoCAD LT object definition that is stored in the drawing, also known as a named object. Symbols can include definitions of blocks, dimensioning styles, layers, linetypes, and text styles.

system variable

A name that AutoCAD LT recognizes as a mode, size, or limit. Read-only system variables, such as DWGNAME, cannot be modified directly by the user.

T

template drawing

A drawing file with preestablished settings for new drawings such as aclt.dwg and acltiso.dwg; however, any drawing can be used as a template. See also initial environment.

temporary files

Data files created during an AutoCAD LT session. AutoCAD LT deletes the files by the time you end the session. If the session ends abnormally, such as during a power outage, temporary files might be left on the disk.

tessellation lines

Lines that help you visualize a curved surface. See also thickness.

text style

A named, saved collection of settings that determines the appearance of text characters-for example, stretched, compressed, oblique, mirrored, or set in a vertical column.

thaw

A setting that displays previously frozen layers. See also freeze. (Associated command: LAYER)

thickness

The distance certain objects are extruded to give them a 3D appearance. (Associated commands: CHPROP, DDCHPROP, ELEV, THICKNESS)

tiled viewports

A type of display that splits the AutoCAD LT graphics area into one or more adjacent rectangular viewing areas. See also floating viewports, TILEMODE, and viewport. (Associated command: VPORTS)

TILEMODE

A system variable that controls whether viewports can be created as movable, resizable objects (floating), or as nonoverlapping display elements that appear side-by-side (tiled). See also viewport. (Associated system variable: TILEMODE)

toolbar

Part of the AutoCAD LT interface containing icons that represent commands.

tracking

A way to locate a point relative to other points on the drawing.

transparent command

A command started while another is in progress. Precede transparent commands with an apostrophe.

U

UCS icon

An icon that indicates the orientation of the UCS axes. (Associated command: UCSICON)

user coordinate system (UCS)

A user-defined coordinate system that defines the orientation of the X, Y, and Z axes in 3D space. The UCS determines the default placement of geometry in a drawing. See also World Coordinate System. (Associated command: UCS)

V

vector

A mathematical object with precise direction and length but without specific location.

vertex

A location where polyline segments meet.

view

A graphical representation of a model from a specific location (viewpoint) in space. (Associated commands: VPOINT, DVIEW, VIEW)

viewpoint

The location in 3D model space from which you are viewing a model. (Associated commands: DVIEW, VPOINT)

viewport

A bounded area that displays some portion of the model space of a drawing. The TILEMODE system variable determines the type of viewport created. 1. When TILEMODE is off (0), viewports are objects that can be moved and resized. (Associated command: MVIEW) 2. When TILEMODE is on (1), viewports are noneditable, nonoverlapping screen displays. See also floating viewports and TILEMODE. (Associated command: VPORTS)

viewport configuration

A named collection of tiled viewports that can be saved and restored. (Associated command: VPORTS)

virtual screen display

The area in which AutoCAD LT can pan and zoom without regenerating the drawing.

W

wireframe model

The representation of an object using lines and curves to represent its boundaries.

working drawing

A drawing for manufacturing or building purposes.

World Coordinate System (WCS)

A coordinate system used as the basis for defining all objects and other coordinate systems.

world coordinates

Coordinates expressed in relation to the World Coordinate System.

WPolygon

A multisided polygon area specified to select objects contained completely within its borders. See also crossing window and CPolygon.

Z

zoom

To reduce or increase the apparent magnification of the graphics display. (Associated command: ZOOM)