                                GLOSSARY


AGNUS
One of the three main Amiga custom chips. Contains the blitter, copper,
and DMA circuitry.

ALIASING DISTORTION
A side effect of sound sampling, where two additional frequencies are
produced, distorting the sound output.

ALT KEYS
Two keys on the keyboard to the left and right of the Amiga keys.

AMIGA KEYS
Two keys on the keyboard to the left and right of the space bar.

AMIGADOS
The Amiga operating system.

AMPLITUDE
The voltage or current output expressed as volume from a sound speaker.

AMPLITUDE MODULATION
A means of increasing audio effects by using one audio channel to alter
the amplitude of another.

ATTACH MODE
In sprites, a mode in which a sprite uses two DMA channels for additional
colors. In sound production, combining two audio channels for
frequency/amplitude modulation or for stereo sound.

AUTOMATIC MODE
In sprite display, the normal mode in which the sprite DMA channel, once
it starts up, automatically retrieves and displays all of the data for a
sprite. In audio, the normal mode in which the system retrieves sound
data automatically through DMA.

BARREL SHIFTER
Blitter circuit that allows movement of images on pixel boundries.

BAUD RATE
Rate of data transmission through a serial port.

BEAM COUNTERS
Registers that keep track of the position of the video beam.

BIT-MAP
The complete definition of a display in memory, consisting of one or more
bit-planes and information about how to organize the rectangular display.

                            - Glossary 365 -


BITPLANE
A contiguous series of display memory words, treated as if it were a
rectangular shape.

BIT-PLANE ANIMATION
A means of animating the display by moving around blocks of playfield
data with the blitter.

BLANKING INTERVAL
Time period when the video beam is outside the display area.

BLITTER
DMA channel used for data copying and line drawing.

CHIP MEMORY
Memory accessible to the Amiga custom chips. On the current generation of
machines, this section of memory starting at address  (See Fast Memory.)

CLEAR
Giving a bit the value of 0.

CLI
See command line interface.

CLIPPING
When a portion of a sprite is outside the display window and thus is not
visible.

COLLISION
A means of detecting when sprites, playfields, or playfield objects
attempt to overlap in the same pixel position or attempt to cross some
pre-defined boundary.

COLOR DESCRIPTOR WORDS
Pairs of words that define each line of a sprite.

COLOR INDIRECTION
The method used by Amiga for coloring individual pixels in which the
binary number formed from all the bits that define a given pixel refers
to one of the 32 color registers.

COLOR PALETTE
See Color table.

COLOR REGISTER
One of 32 hardware registers containing colors that you can define.

COLOR TABLE
The set of 32 color registers.

COMMAND LINE INTERFACE
The command line interface to system commands and utilities.

COMPOSITE VIDEO
A video signal, transmitted over a single coaxial cable, which includes
both picture and sync information.

CONTROLLER
Hardware device, such as mouse or light pen, used to move the pointer or
furnish some other input to the system.

                            - 366 Glossary -


COORDINATES
A pair of numbers shown in the form (x,y), where x is an offset from the
left side of the display or display window and y is an offset from the
top.

COPPER
Display-synchronized coprocessor that resides on one of the Amiga custom
chips and directs the graphics display.

COPROCESSOR
Processor that adds its instruction set to that of the main processor.

CURSOR KEYS
Keys for moving something on the screen.

DATA FETCH
The number of words fetched for each line of the display.

DELAY
In playfield horizontal scrolling, specifies how many pixels the picture
will shift for each display field. Delay controls the speed of scrolling.

DENISE
One of the three main Amiga custom chips. Contains the circuitry for the
color pallete, sprites, and video output.

DEPTH
Number of bit-planes in a display.

DIGITAL-TO-ANALOG CONVERTER
A device that converts a binary quantity to an analog level.

DIRECT MEMORY ACCESS
An arrangement whereby intelligent devices can read or write memory
directly, without having to interrupt the processor.

DISPLAY FIELD
One complete scanning of the video beam from top to bottom of the video
display screen.

DISPLAY MODE
One of the basic types of display; for example, high or low resolution,
interlaced or non-interlaced, single or dual playfield.

DISPLAY TIME
The amount of time to produce one display field, approximately 1/60th of
a second.

DISPLAY WINDOW
The portion of the bit-map selected for display. Also, the actual size of
the on-screen display.

DMA
See direct memory access.

DUAL-PLAYFIELD MODE
A display mode that allows you to manage two separate display memories,
giving you two separately controllable displays at the same time.

                            - Glossary 367 -


EQUAL-TEMPERED SCALE
A musical scale where each note is the 12th root of 2 above the note
below it.

EXEC
Low-level primitives that support the AmigaDOS operating system.

FAST MEMORY
Memory not accessable by the custom chips. Care must be taken to present
only chip memory address to the custom chips. See Chip Memory.

FONT
A set of letters, numbers, and symbols sharing the same size and design.

FREQUENCY
The number of times per second a waveform repeats.

FREQUENCY MODULATION
A means of changing sound quality by using one audio channel to affect
the period of the waveform produced by another channel. Frequency
modulation increases or decreases the pitch of the sound.

GENLOCK
An optional feature that allows you to bring in a graphics display from
an extemal video source.

HIGH RESOLUTION
A horizontal display mode in which 640 pixels are displayed across a
horizontal line in a normal-sized display.

HOLD-AND-MODIFY
A display mode that gives you extended color selectionup to 4,096 colors
on the screen at one time.

INTERLACED MODE
A vertical display mode where 400 lines are displayed from top to bottom
of the video display in a normal-size display.

JOYSTICK
A controller device that freely rotates and swings from left to right,
pivoting from the bottom of the shaft; used to position something on the
screen.

LIGHT PEN
A controller device consisting of a stylus and tablet used for drawing
something on the screen.

LOW RESOLUTION
A horizontal display mode in which 320 pixels are displayed across a
horizontal line in a normal-sized display.

MANUAL MODE
Non-DMA output. In sprite display, a mode in which each line of a sprite
is written in a separate operation. In audio output, a mode in which
audio data words are written one at a time to the output.

                            - 368 Glossary -


MIDI
A standardized musical instrument interface used by many musical
instruments.

MICROSECOND (US)
One millionth of second (1/1,000,000).

MILLISECOND (MS)
One thousandth of second (1/1,000).

MINTERM
One of eight possible logical combinations of data bits from three
different data sources.

MODULO
A number defining which data in memory belongs on each horizontal line of
the display. Refers to the number of bytes in memory between the last
word on one horizontal line and the beginning of the first word on the
next line.

MOUSE
A controller device that can be rolled around to move somethlng on the
screen; also has buttons to give other forms of input.

MULTITASKING
A system in which many tasks can be operating at the same time, with no
task forced to be aware of any other task.

NANOSECOND (NS)
One billionth of a second (1/1,000,000,000).

NON-INTERLACED MODE
A display mode in which 200 lines are displayed from top to bottom of the
video display in a normal-sized display.

NTSC
National Television Standards Committee specification for composite
video. The base Amiga crystal frequency for NTSC is 28.63636 Mhz.

OVERSCAN
Area scanned by the video beam but not visible on the video display
screen.

PADDLE CONTROLLER
A game controller that uses a potentiometer (variable resistor) to
position objects on the screen.

PAL
A European television standard similar to (but incompatible with) NTSC.
Stands for "Phase Altemate Line." The base Amiga crystal frequency for
PAL is 28.37516 Mhz.

PARALLEL PORT
A connector on the back of the Amiga that is used to attach parallel
printers and other parallel add-ons.

PAULA
One of the three main Amiga custom chips. Contains audio, disk, and
interrupt circuitry.

                            - Glossary 369 -


PITCH
The quality of a sound expressed as its highness or lowness.

PIXEL
One of the small elements that makes up the video display. The smallest
addressable element in the video display.

PLAYFIELD
One of the basic elements in Amiga graphics; the background for all the
other display elements.

PLAYFIELD OBJECT
Subsection of a playfield that is used in playfield animation.

PLAYFIELD ANIMATION
See bit-plane animation.

POINTER REGISTER
Register that is continuously incremented to point to a series of memory
locations.

POLARITY
True or false state of a bit.

POTENTIOMETER
An electrical analog device used to adjust some variable value.

PRIMITIVES
Amiga graphics, text, and animation library functions.

QUANTIZATION NOISE
Audio noise introduced by round-off errors when you are trying to
reproduce a signal by approximation.

RAM
Random access (volatile) memory.

RASTER
The area in memory that completely defines a bit-map display.

READ-ONLY
Describes a register or memory area that can be read but not written.

RESOLUTION
On a video display, the number of pixels that can be displayed in the
horizontal and vertical directions.

ROM
See read-only memory.

SAMPLE
One of the segments of the time axis of a waveform.

SAMPLING RATE
The number of samples played per second.

SAMPLING PERIOD
The value that determines how many clock cycles it takes to play one data
sample.

SCROLLING
Moving a playfield smoothly in a vertical or horizontal direction.

SERIAL PORT
A connector on the back of the Amiga used to attach modems and other
serial add-ons.

                            - 370 Glossary -


SET
Giving a bit the value of 1.

SHARED MEMORY
The RAM used in the Amiga for both display memory and executing programs.

SPRITE
Easily movable graphics object that is produced by one of the eight
sprite DMA channels and is independent of the playfield display.

STROBE ADDRESS
An address you put out to the bus in order to cause some other action to
take place; the actual data written or read is ignored.

TASK
Operating system module or application program. Each task appears to have
full control over its own virtual 68000 machine.

TIMBRE
Tone quality of a sound.

TRACKBALL
A controller device that you spin with your hand to move something on the
screen; may have buttons for other forms of input.

TRANSPARENT
A special color register definition that allows a background color to
show through. Used in dual-playfield mode.

UART
The circuit that controls the serial link to peripheral devices, short
for Universal Asynchronous Receiver/Transmitter.

VIDEO PRIORITY
Defines which objects (playfields and sprites) are shown in the
foreground and which objects are shown in the background. Higher-priority
objects appear in front of lower-priority objects.

VIDEO DISPLAY
Everything that appears on the screen of a video monitor or television.

WRITE-ONLY
Describes a register that can be written to but cannot be read.

                            - Glossary 371 -

End.
