AmigaOS Manual: Workbench Glossary

This glossary provides definitions of terms used in the Amiga manuals.

acceleration

An option, selected through the Input editor, that causes the pointer movement to increase as the mouse is moved at a constant speed. Acceleration provides a higher degree of control for small mouse movements and less control, but greater mouse speed, for large movements.

action gadget

A gadget in a window that performs an operation in the window when you select the gadget. Common action gadgets are Save, Continue, and Cancel.

active

Used in reference to the screen, Shell window, or Workbench window that is accepting input..

Advanced Graphics Architecture (AGA)

An Amiga custom chip set that delivers more displayable colors and improved performance.

alias

An alternative name for an AmigaDOS command or command string, specified with the ALIAS command.

AmigaDOS

The disk operating system (DOS) used by Amiga computers. A disk operating system provides the basic functions of the computer.

AppIcon

An icon created and used by an application.

application

A program or collection of programs that perform a specific task, such as a word processor, database, or video title.

AppWindow

An application window into which you can drag an icon to load the icon file into the application. The MultiView window and Amiga file requester are AppWindows.

archive

1. (n) A backup copy of a file or files.
2. (v) To copy files to disk or tape for backup purposes.

argument

An additional piece of information, such as a file name, value, or option, included along with a command. This information determines the exact actions of the command.

argument passing

Specifying parameters on the command line for a program or command to follow.

ASCII (American Standard Code for Information Interchange)

A standardized format for text that assigns code numbers to characters, allowing the exchange of information between different types of computers.

aspect ratio

The proportion of an image's height to its width.

assign

To link a logical device name to a directory name with the ASSIGN command. This lets programs that use that directory use a single device name in all cases. For example, the device name T: is commonly assigned to the directory name RAM:T.

attributes

A series of flags stored with every file. Attributes indicate file type and control the operations (read, write, delete, and so forth) permissible on the file. Also called protection bits.

autoscroll

To automatically move a screen when the pointer reaches the edges of the viewable area.

backdrop

A special type of window that has no borders, is as large as the screen, and is always behind all other windows on the screen.

backup

A copy of a file on disk or tape used to replace lost data.

back up

To make a backup copy.

baud rate

The speed at which a device receives or transmits information in serial communication. Roughly equivalent to bits per second.

binary

The base-2 number system that uses only the digits 0 and 1.

bit

A single binary digit (1 or 0).

bitplane

An area of RAM that holds screen graphics data. Each bit in a bitplane controls one screen pixel. The number of bitplanes for a screen controls the maximum number of simultaneous colors possible for that screen.

block

1. A contiguous series of bytes (usually 512) treated as a single logical unit in RAM or permanent storage media.
2. A user-marked area of a text file.

boot

To start the system by reading the information needed from a storage device, such as a floppy or hard disk, into the computer's memory. Also refers to items used in this process: the boot disk. (See reboot.)

bootable

Refers to a device from which the Amiga can boot. A bootable disk must contain all the system files needed for the computer to start operation.

Bridgeboard

An expansion board from Commodore that allows hardware emulation of PC-compatible computers.

brush

An IFF graphics file, usually a section cut from a full-sized picture.

buffer

A temporary storage area in RAM.

bug

An error in software or hardware.

busy pointer

An image of a stopwatch that appears in place of the normal pointer when the Workbench is busy and cannot accept further input. Also called the wait pointer.

byte

A unit of memory consisting of eight bits, usually equivalent to one character.

cache memory

A temporary area in memory with extremely fast access that improves the system performance.

catalog

The files that contain the system texts and messages translated to a different language.

CD-ROM

A read only storage media. Stores upward of 550 MB on a disk similar to an audio compact disc.

check box

A gadget that lets you turn an option on or off. When a check mark appears in the box, the option is selected, or on.

chip

A miniaturized electronic circuit, housed in a small, black, rectangular block edged by metal connector pins. A computer is made up of a variety of specialized chips.

Chip RAM

The area of RAM accessible to the Amiga's custom chip set. This memory is used for graphics and sound data. Also called graphics memory.

clear

1. To change a bit or flag to its 0, off, or disabled state. Opposite of set.
2. To erase a screen or window display.

CLI (Command Line Interface)

A means of communicating with a computer by issuing commands from the keyboard. The Shell is the Amiga's CLI.

click

To press and release a mouse button. Refers to the selection (left) mouse button unless otherwise specified.

Clipboard

An area in memory that is used to store text and graphics while they are being transferred between programs.

close

To remove a window from the screen, to end a program, or to finish the access to a data file.

close gadget

A gadget that can appear in the upper left corner of a window to allow you to close the window.

cold boot

To boot the Amiga from a powered off state.

color correction

A printing option, selected through the PrinterGfx editor, that tries to better match the colors of a printout to the colors on the screen.

command

A statement given to the Amiga to perform a task or achieve a result.

command history

A feature of the Shell that allows you to recall previously entered command lines by using the cursor keys.

command line

The line on which commands and their arguments are typed. Also, all the information that has been typed on the line.

console window

A window used for the input and output of text, such as a Shell window.

Control-key combination

A key combination that performs a special function, entered by holding down Ctrl while pressing another key on the keyboard. Some Control-key combinations are executed as soon as they are pressed, such as when Ctrl+C is used to abort the execution of an AmigaDOS command. Some produce a reversed character image and have no immediate effect.

coprocessor

A separate processor chip that assists the CPU by performing specific tasks, such as mathematical computations or rapid data transfer.

copy and paste

The act of copying a block of text or graphics and inserting it at a new location.

CPU (Central Processing Unit)

The "brain" of a computer; the integrated circuit chip primarily responsible for executing the instructions in a program.

current directory

The current location in the directory structure. The directory AmigaDOS uses as the default directory to operate within, if no other directory is specified.

current window

The highlighted window that accepts input from the keyboard. A Shell window is current when it is opened.

cursor

A highlighted rectangle or vertical bar on the screen used to indicate text position.

cycle gadget

A gadget for selecting one of several options. One option is displayed at a time and as the gadget is selected, the other options become visible. The displayed option is the selected option.

cylinder

A logical division of a magnetic storage disk. Amiga 3.5 inch floppy disks are divided into 80 cylinders during the formatting process.

data

A collection of information.

dead key

A key, or key combination, that modifies the output of the next key to be pressed. For example, on an American keyboard. Alt+H superimposes a caret (^) symbol over the next key to be pressed. Alt+H is a dead key combination.

debug

To find and fix mistakes in software or hardware.

default

A value or action assumed if you have not specified something else.

Default Tool

A tool specified in a project icon's Information window. When the project icon is opened, the Default Tool is automatically loaded and run.

delete

To erase or discard a file, buffer, or other stored item.

delimiter

A special character marking the beginning and end of a string.

density

The number of printer dots per inch. Many printers support several print densities. Usually, the higher the density, the darker and sharper the printout.

depth gadget

A gadget that may appear in the upper right corner of a window or screen for moving that window or screen in front of or behind other windows or screens. This is sometimes referred to as depth arranging.

destination

The device, directory, or file that is receiving information.

device

A physical mechanism, such as a printer or disk drive, or a software entity (logical device), such as CON: or NIL:, used as a source or destination for information.

device name

A short name, such as DF0:, PC1:, or PRT:, that identifies a particular hardware or software device. Device names must end in a colon (:).

directory

A subdivision in a computer's filing system used to organize files and other directories (subdirectories). Directories are represented on the Workbench by drawer icons.

disk

A medium for mass storage of computer data. Most computer disks store information magnetically; optical (laser-read) disks are also used.

disk drive

A storage device that reads and writes data from and to a storage disk such as a floppy disk.

disk operating system (DOS)

The software that controls the basic input and storage functions of a computer.

display box

A rectangular box, usually under a scroll gadget or next to a selection gadget, that displays the current selection. You cannot edit a display box.

display mode

A name given to the set of parameters, such as resolution and scan frequency, that define a screen. For example, a High Res display mode is 640 pixels wide and 200 pixels high (for NTSC Amigas).

dithering

1. Creating smoother color or grey scale shading of screen or printed displays by altering pixel color or density. The PrinterGfx and PrinterPS Preferences editors provides several settings for automatic dithering of printed graphics.
2. Creating the illusion of a color by using a pattern of other colors. For example, creating the illusion of purple by alternating pixels of red and blue.

double-click

To quickly press and release the selection button twice.

drag

To move an icon, window, gadget, or screen across the display by pointing to the object, holding down the selection button, and moving the mouse.

drag selection

The process of selecting several icons at once by holding down the selection button and using the mouse to draw a box around the icons you want to select. When you release the mouse button, all the icons in the box are selected.

drawer

A subdivision of a disk storage area. A drawer corresponds to an AmigaDOS directory.

drive name

The device name assigned to a disk drive, such as DF0: or DH1:.

dump

A printout of the image displayed on the screen.

ECS (Enhanced Chip Set)

The upgraded versions of the Amiga's Agnus and Denise coprocessor chips. The Enhanced Chip Set offers additional display modes (ECS modes) and expands previous graphics capabilities. Many of the benefits of the ECS are available only in conjunction with Release 2 or higher of the operating system.

editor

A program that lets you create and/or modify certain types of files. The Amiga provides Preferences editors to change Prefs settings and the text editors, MEmacs and ED, for changing text files.

escape sequence

A sequence of characters, beginning with the Escape character, that performs a special function when entered on a command line or printed as part of a string. Escape sequences are typically used to alter the style of type used by a printer or in a console window.

execute

To carry out the instructions in a command line, program, or script.

extended selection

The process of selecting several icons at once by holding down Shift while selecting each icon with the mouse.

extension

A sequence of characters beginning with a period, such as .info, added to the end of a filename to identify the type of file.

Extra Halfbrite

A special graphics mode that doubles the number of colors on the screen by duplicating existing colors at half their brightness.

Fast RAM

General memory used by programs and data. As the name implies, normally faster than Chip RAM.

field

The screen area behind the text of a Workbench icon label. The color of the field can be changed with the Font editor.

file

An organized collection of data referred to by a name and stored on some type of media.

file system

The organization and software that controls the data, files, and directories stored on a volume. The primary types of Amiga file systems are FFS (FastFileSystem) and OFS (OldFileSystem).

floppy disk

A removable magnetic storage medium. The Amiga uses 3.5 inch, double-sided, floppy disk in a rigid plastic case.

font

Also called typeface. A particular design of a set of letters, symbols, and numbers used for text display, such as Topaz and Helvetica. Fonts are usually available in several sizes, defined in points (10 point, 12 point, and so on).

format

1. To prepare a disk for use with the Amiga. Formatting a disk erases all previously stored data.
2. A way of describing the proper syntax for AmigaDOS commands.

fragmentation

A scattered distribution of data on a disk or in memory. Disk fragmentation results in slower disk performance; memory fragmentation can prevent some programs from running properly.

function keys

Keys at the top of the Amiga keyboard, labeled F1 to F10, that can be programmed to perform special tasks.

gadget

Any of various programmed graphic images that may appear in a window, requester, or screen and can be manipulated with the mouse to perform a certain function. Each gadget is of a specific type and performs a specific action. Most gadgets appear raised and when selected, appear to sink into the screen.

genlock

A piece of hardware that allows Amiga graphics to be overlaid onto another video source, for example, from a camera or VCR. A genlock is typically used for applying titles or captions to video media.

ghosting

Displaying menu or gadget items on the screen less distinctly than normal to indicate that they are currently unavailable.

graphics memory

See Chip RAM.

GUI (Graphical User Interface)

A visually-oriented system allowing you to tell a computer what to do by manipulating graphic symbols rather than by typing in commands. The Workbench is the Amiga GUI.

HAM (Hold And Modify)

An Amiga graphics mode that allows the full Amiga color palette to be displayed on the screen.

handshaking

The electronic protocol required for serial communication between two computing devices.

hard disk

A high-speed, large-capacity mass-storage device from which the disks usually cannot be removed. Often called a hard drive or hard disk drive.

hierarchical

A term used to describe the multi-leveled AmigaDOS file structure in which directories can contain other directories and/or files.

history buffer

A section of memory that stores the most recent commands for a given Shell.

hold down

To continually press a mouse button until instructed to release it.

hot key

A key or key combination used by Commodity Exchange programs to open a hidden window.

hot spot

The pixel in a pointer, normally the tip of an arrow or the center of a crosshair, that must be touching an object on the screen to select it.

icon

An image appearing on the screen to represent a disk, drawer, project or tool. Icons can be moved and selected with the mouse to allow you to work with the items they represent.

IFF (Interchange File Format)

The standardized format in which the Amiga stores picture, sound, and other types of data.

.info file

A file containing the image and position data for an icon (referred to as "dot-info").

initialize

A synonym for format.

input buffer

An area of memory used during serial communication to hold incoming information.

interlace

A property of some Amiga display modes that doubles the vertical screen resolution.

Internal

Refers to an AmigaDOS command that is built into the Shell, rather than loaded from disk.

KB (Kilobyte)

1024 bytes. Often abbreviated as K.

keyboard shortcut

A method for performing a mouse action by pressing a key or key combination.

keymap

A file that determines the arrangement of characters on the keyboard and determines the meaning of each key. Different languages have different keymaps.

keyword

A word recognized by an AmigaDOS command or a Tool Type entry as ientifying an argument or specifying an option.

Kickstart

Refers to the portion of the Amiga operating system that is in ROM.

library

An integrated set of functions and data that can be used by different programs. Libraries can be found in ROM and in the LIBS: drawer.

macro

A single command that represents a sequence of commands. Many editors and applications support the use of macros to facilitate commonly used command sequences. ARexx programs are often called macros.

MB (Megabyte)

1024KB (1,048,576 bytes). Often abbreviated as M or Meg.

memory

The Amiga's internal storage circuitry that holds programs and data. The Amiga has Chip (graphics) memory. Fast (normal) memory, and ROM (Read Only Memory). The amount of RAM (Random Access Memory) limits the size and number of programs that can be operating within the Amiga at one time.

menu

A list of on-screen options, displayed by using the menu button, from which you can choose commands that control a program.

menu bar

The list of headings that appears across the top of the screen when the menu button is held down.

menu button

The right mouse button.

menu item

An option that appears in a menu. For example, New Drawer is the first menu item in the Workbench's window menu.

modem

A device allowing serial communication over telephone lines.

monitor

A video display terminal on which a computer's visual output is shown. There are many types of monitors; the Amiga's standard output uses an analog RGB color monitor to display both graphics and text.

mouse

The device used to move the pointer on the screen and to communicate with the Amiga. Ist buttons can be used for displaying menus, and for selecting and dragging icons, windows and screens.

multiscan

A type of video monitor than can accept several different scan rates (types of video output).

multitasking

The ability to Perform more than one operation, or task, at a time. The Amiga's multiasking operating system can have several independent programs running at once. For instance, you could simultaneously be displaying an animation, playing a sound file, communicating with another computer, and formatting a floppy disk.

nonproportional font

A font, such as Topaz, in which each character takes up an equal amount of space. For example, an uppercase W is allotted the same amount of space as a lowercase 1. Also calls a monospaced font.

offset

To shift or move over.

open

To make the selected object available for use. Open an icon by double-clicking on it or by selecting it then choosing the Open menu item from the Icons menu. When you open a disk or drawer icon, a window appears, displaying its contents. When you open a project or tool icon, a program is started.

operating system (OS)

Software, in ROM or supplied on floppy or hard disk, that controls the basic functions of a computer.

overscan area

The normally unused area surrounding a standard-size screen. The Overscan editor allows you to expand your screen to fill this area.

overwrite

To write information to memory, a file, or disk, replacing any information that previously was stored there.

parallel

An interface port that transfers data one complete byte (8 bits) at a time, contrasted to a serial interface that sends a single bit at a time. The Amiga has an external parallel port to which a printer can be connected.

parent

The window from which another window was generated. The directory that contains the current directory a drawer.

parity

A method of detecting errors in serial communication by attaching an extra bit to bytes of data.

partition

A section of the hard disk that the system treats as if it were a separate drive.

path

The series of volume and drawer names that define the location of a file.

pattern matching

An AmigaDOS feature that lets you specify file and directory names by using wildcard characters. With wildcards, you can create search patterns that allow you to refer to a number of files whose names share a common text pattern without naming each file individually.

peripheral

An external hardware device connected to the Amiga.

pitch

The number of characters printed in a horizontal inch.

pixel

The dots of light that make up the Amiga screen display. A pixel is the smallest unit of display information on a given screen. Derived from "Picture Element".

point

(v) To place the mouse pointer so that its hot spot is touching the object pointed to.: (n) The unit of measurement of vertical font size. Traditionally this is 1/72 of an inch; on the Amiga it means one screen pixel.

pointer

An image on the screen, usually arrow-shaped, that moves as you move the mouse. Use the pointer to select icons and gadgets and to choose menu items.

PostScript printer

A high-resolution printer that can accept text and graphics information in the PostScript page description language.

Preferences (Prefs)

A Workbench drawer containing editors that let you configure and customize your Amiga environment, such as changing the colors of your screen and setting the specifications for communication through the serial port.

printer driver

A program that enables the Amiga to communicate with a given printer. A printer driver works as a translator between a computer and a printer, taking the information in a standardized form (ASCII characters and ANSI escape sequences) from the computer and presenting it to the printer in a format that the printer can understand.

program

A series of instructions that tell the Amiga how to perform certain tasks. Applications and system software are programs.

project

A file in which information crated or used by a tool is stored. For example, files created with a text editor or paint program are projects.

prompt

A message or symbol that indicates that text input to the computer is expected.

protection bits

(See attributes.)

pseudo-icon

An icon that is displayed for an object that does not have a .info file when the Show All Files menu item is chosen.

pure

Describes a command or program that can be made resident. If a file is pure, the p attribute is set.

qualifier

A key, such as Shift, Ctrl, or Alt, that change the Amiga's interpretation of a simultaneous or subsequent keystroke or mouse click. Commonly used with Commodity Exchange programs.

radio button

A circular gadget beside an option on a list. To select an option, select its radio button. You can only option from the list at a time.

RAM (Random Access Memory)

Part of the Amiga's internal memory that can be used for data storage and is directly accessible by the CPU. Applications are loaded into RAM from disk and use additional RAM to process and store data while the computer is on. Data in RAM is lost when the Amiga is rebooted or powered off.

Ram Disk

A section of RAM set aside to function as if it were a disk drive. This is much faster than a physical drive, since there are no mechanical elements.

read

To retrieve stored information.

Read Only

If disk status is Read Only, you can only look at the contents of the disk, you cannot alter them.

Read/Write

If disk status is Read/Write, you can both look at and alter the contents of the disk.

reboot

To reset the Amiga by pressing Ctrl, left Amiga, and right Amiga. This is roughly equivalent to turning the power off, then on again. Memory is reset. Also called warm boot.

redirect

To change the source or destination of a command's input or output from the default by using the special characters < or >.

requester

A window that appears when the system needs a response from you. A requester contains action gadgets that give you a choice of continuing or aborting the operation in progress. To exit the requester, you must select one of the displayed gadgets.

resident

Describes a command or program that has been copied into memory, with the RESIDENT command, for quicker execution. Resident commands are specially set up to prevent reloading on subsequent executions. Only pure files can be made resident.

resolution

The dimensions, in pixels, associated with a particular display mode. For example, a normal NTSC High Res screen has a resolution of 640 (horizontal) by 200 (vertical) pixels.

RGB (Red-Green-Blue)

A type of video signal in which the three primary color signals are sent separately. Standard Amiga output uses an RGB monitor.

ROM (Read Only Memory)

Permanent memory that is pre-programmed with system instructions and does not change. The contents of ROM are not affected by user commands or program operation.

root block

The area of a disk that contains the name of the disk and information pertaining to the disk layout. If the root block is erased, you cannot retrieve any information from the disk -- it is effectively blank.

root directory

The main directory on a volume. The root directory is at the top of the filing hierarchy and is created when a volume is formatted. All other directories on the volume exist within the root. The root directory is specified by the volume name followed by a colon.

scaling

Changing the size of an image or font for printing or display. Usually, a screen image is scaled down to a smaller size for printing, but you can also enlarge, or scale up, an image.

screen

An area of the display that has certain graphical attributes, such as resolution and colors. Screens are always at least the full width of the viewable area. The Amiga can have several screens with different attributes open and visible at once.

script

A text file containing a series of commands that can be automatically executed to perform a complex or repetitive task. An example of a script is the Startup-sequence file executed when you boot your Amiga.

scroll

To move through the viewing area of a window or list.

scroll arrows

Gadgets that may appear in a window to allow you to move the viewing area continuously.

scroll bar

The highlighted area within the scroll boy that can be dragged to display the hidden contents of a window. It changes in size to indicate the portion of the window that is currently visible.

scroll box

The shaded area within which the scroll bar can be dragged. You can click in the scroll box to move the scroll bar.

scroll gadget

A gadget that can appear in a window to let you move through a list of options or through the viewing area of a window. A scroll gadget is made up of the scroll bar, scroll box, and scroll arrows.

scrolling list

The options that appear inside a scroll gadget. If the list is too long to be displayed in the scroll gadget, you can use the scroll bar or scroll arrows to move (scroll) through the list.

search path

The list of directories that AmigaDOS uses when it is looking for a command. Directories are added or removed from the search path with the PATH command.

select

To choose an item to work with by pointing to it with the mouse, then clicking the selection button.

selection button

The left mouse button.

selection gadget

A gadget from which you can choose one of several displayed options, often used for colors.

serial

An interface port that transfers data a single bit at a time, contrasted to a parallel interface which sends one complete byte (eight bits) at a time. The Amiga has an external serial port to which a modem, MIDI interface, or printer is often connected.

set

To change a bit or flag to its on or enabled state. Opposite of clear.

Shell

The command line interface used to send typed commands to the Amiga. The Shell is a console window that supports many special features, such as command-line history, aliases, and copy and paste operations.

sizing gadget

A gadget that can appear in the lower right corner of a window to allow you to enlarge or shrink the size of the window.

slider gadget

A gadget from which you can select a value by dragging a bar through the gadget. As you move the slider bar, different values are displayed.

slider value

A number that appears next to a slider gadget to indicate the currently selected value.

smoothing

A printing option available in the PrinterGfx editor that attempts to eliminate, or smooth, jagged lines that can sometimes appear in printouts.

snapshot

To save the positions of a window and/or the icons within it.

source

A device, drawer, or file that is supplying information. for example, when you copy a disk, the disk you are copying is the source disk.

stack

A special area of RAM reserved by a program for temporary storage.

Startup-sequence

An AmigaDOS script file, executed when the Amiga is booted, that helps set up the hardware and directory systems.

stop bits

Extra bits added to signal the end of a character, used during serial communication.

string

A piece of text treated as a single unit.

subdirectory

A directory that is within another directory; equivalent to a drawer within a drawer.

submenu

A secondary menu that appears when some menu items are highlighted. If a menu item has a submenu, a » symbol appears to the right of the menu item.

swap

To alternately place different floppy disks into the same drive, as when performing a single-drive disk copy.

SYS

The name assigned to the volume that the Amiga searches for its system files and directories. Usually the volume booted from.

text gadget

A rectangular box in which you can type information, such as a filename or command. Text gadgets are used by the Rename and Execute Command menu items, as well as many programs.

threshold

A PrinterGfx value related to color intensity. It determines which colors are printed as black and which are printed as white during black-and-white printing.

timestamp

The date and time associated with a file or directory. This is usually the date and time when the file or directory was created or last modified.

title bar

The top border of a screen or window, which commonly displays the name of the screen or window.

toggle

An option that can be switched between two states, such as on and off.

tool

A program that creates or uses data, such as a text editor or paint program.

Tool Type

An optional parameter that you can enter in an icon's Information window to control a program. For example, if you enter the SECONDS Tool Type in the Clock's Information window, the Clock displays the seconds when it is opened.

Trashcan

A directory for storing files that you want to delete.

type ahead

A feature of the Shell that lets you enter commands as a previous command's output is being displayed.

User-startup

A user-created file containing specific system settings that are red and executed during the system startup sequence.

volume

A mounted storage unit, such as a floppy disk or hard disk partition.

volume name

The name of a volume, as distinguished from its device name. Renaming a disk changes its volume name, not its device name.

wildcard

A symbol used in pattern matching to represent a range of possible values, such as when specifying filenames that all start or end with the same character. The question mark (?), for example, is used as a wildcard to match any single character.

window

A rectangular screen area that can accept or display information. A window has a title bar identifying it and may contain gadgets in its border.

Workbench

The Amiga's icon-based, graphical user interface.

write

To record data in memory or on a storage medium such as a floppy disk.

write-enable

To allow information to be written onto a storage device. When a floppy disk is write-enabled or Read/Write, a small, plastic tab is covering the hole in the corner of the disk.

write-protect

To prevent information from being written onto a storage device. Floppy disks have a plastic tab that can be moved to write-protect the entire disk, making it read-only. Also called write-inhibit.

zoom gadget

A gadget that may appear in the upper right corner of a window to allow the window to alternate between two sizes.