Appendix C - Glossary

	A

archive file:	A file which is formed by concatenating several files, often 
using an encoding method that compresses the original files.

area-fill pattern:	 A two-dimensional pattern of pixels used to fill 
			 regions bounded by lines and curves.

ascent:	Font metric; the distance in pixels from the base line to the top of 
			the highest character in the font.

ASCII character code:	American Standard Code for Information Exchange. A 
standard code for representing both control and graphic characters. Each 
character is represented by a 7-bit code, or by an 8-bit code if a parity bit 
is included. This code is widely used for information exchange among data 
processing and communications systems.

	B

background color:	The color to which the 0s in bit maps and 
area-fill patterns are set; also the color in which the pixels within the 
rectangles surrounding bit-mapped character shapes are drawn. 
The pixel value corresponding to the background color is pixel-replicated and 
loaded into the COLOR0 register of the TMS340 graphics processor.

base line:	An invisible reference line corresponding to the bottom of the 
characters in a font, excluding the descenders.

binary image file:	A file containing the binary image of a program 
or a block of data exactly as it appears when loaded into memory.

binsrc:	A  utility program for converting a binary image file to a C or 
assembly language file.

BitBlt:	Bit-aligned block transfer. A BitBlt operation copies a bit map from 
one location in memory to another. The copy operation may involve combining 
each pair of corresponding source and destination bits according to one of 16 
possible Boolean operations. (Also see PixBlt. )

bit map:   The digital representation of an image in which bits are mapped to
pixels. This is a special case of a pixel array in which the pixel size is 1 
bit. (See pixel array.)

bit-mapped font:   A digital representation of a font in which the
insert	shapes are stored as bit maps.

blanking interval:	The time during which the monitor's electron beam is 
extinguished during the horizontal and vertical retrace periods.

block font:	A font that emulates the cell-mapped text output by older, 
character-ROM-driven terminals and by display adapters such as the VGA.

block write cycle:  A type of video-RAM write cycle that is typically used to
rapidly fill an area of the frame buffer with a particular pixel value. Block 
write cycles are supported by TI's TMS44C251 1-megabit video RAM. Prior to the 
block write cycle, a 4-bit color latch within each VRAM is loaded with 4 bits 
of pixel data. During the block write cycle, the level input to the VRAM on 
each of its 4 data pins controls whether the color latch is written to a 
particular region of the memory; in other words, up to 16 bits may be written 
within the VRAM during a single block write cycle.

Bresenham's algorithm:	An algorithm first described by J. E. Bresenham that is 
widely used for drawing straight lines on raster displays.

bulk initialization:A method for rapidly replicating a pixel value through all
or a portion of video memory. This method can be utilized only with video RAM 
devices that support serial-register-to-memory cycles.

	C

clipping window:   The rectangular region on the screen to which graphics
output is restricted. No drawing is allowed to occur outside the current 
clipping window.

COFF:	Common Object File Format. Originally defined by AT&T, this format is
used for the object files created by the TMS340 Family assembler, C compiler 
and linker. Details are presented in the TMS340 Family Code Generation Tools 
User's Guide.

cof2bin:  A  utility program for converting a COFF file to a binary image
file.

color lookup table:	(See palette.)

color palette:		(See palette.)

conditional assembly statements: Directives to the assembler that control
whether particular blocks of assembly language statements are assembled or 
ignored.

conditional compilation statements:	Directives to the compiler that control 
whether particular blocks of high-level-language statements are compiled or 
ignored.

Core Primitives Library: The TMS340 Graphics Library consists of two parts, the
Extended Primitives and the Core Primitives. This is similar to TIGA. The Core 
Primitives include the functions for initializing and querying the graphics 
environment, as well as rudimentary text and graphics capabilities.

	D

DAC:	Digital-to-analog converter. A device that converts a digital input 
code to an analog output voltage or current. The output level is the analog
representation of the digital value input to the device.

dearchive: The process of extracting the original files from an archive file.

descent:	Font metric; the distance in pixels from the base line to the 
bottom of the lowest descender in the font.

display memory:	The portion of memory that can be displayed. The display 
memory contains one or more video pages that can be output to a monitor. In a 
TMS34010- or TMS34020-based display system, the display memory typically 
consists of video RAM devices.

display page:	The video page that is currently displayed on the monitor.

double buffering: A technique for achieving flickerless animation that requires
two video pages (or frame buffers). While the graphics processor draws to one 
page, the alternate page is displayed on the monitor. When the graphics output 
to the drawing page is completed, the old drawing page becomes the new display 
page, and vice versa.

DRAM refresh:	Dynamic random-access memory refresh. The operation of 
maintaining data stored in DRAM devices. Data are stored in DRAMs as electrical 
charges across a grid of capacitive cells, and the charge stored in a cell will 
leak off over time unless it is refreshed.

drawing coordinate system:	The x-y coordinate system in which all drawing 
(graphics output) operations are specified. The drawing origin can be moved 
relative to the fixed screen origin. The x coordinates increase from left to 
right, and y coordinates from top to bottom.

drawing origin:	The position of the x-y origin on the display surface, used as 
a reference for positioning graphics output. The drawing origin can move 
relative to the screen origin, which is fixed in the top left corner of the 
screen.

drawing page:	The video page that is currently the designated target of all 
graphics output commands.

	E

em, em space:	Font metric; equal to the square of the type size used.

Extended Primitives Library:	The TMS340 Graphics Library consists 
of two parts, the Extended Primitives and the Core Primitives. This is similar 
to TIGA. The Extended Primitives comprise most of the sophisticated graphics 
functions, including lines, curves, fills, patterns and proportionally-spaced
text.
	F

field:	1) A group of contiguous bits in a register or memory that are dedi-
	cated to a particular function or represent a single entity. 
	2) A software-configurable data type in a TMS34010 or TMS34020
	whose length can be programmed to be any value in the range 1 to 32
	bits.

font:	A complete assortment of characters of a particular size and typeface.

font size: The size of a bit-mapped font in the graphics library, specified in
terms of the height in pixels of the font rectangle. This height is equal to 
the sum of the font's ascent and descent parameters.

font table:	A data structure within the TMS340 Graphics Library that 
contains pointers to all currently installed fonts.

foreground color:  The color to which solid lines, curves, and filled areas are
set; the color to which the 1s in bit maps and area-fill patterns are set; also
the color in which bit-mapped character shapes are drawn. The pixel value 
corresponding to the foreground color is pixel-replicated and loaded into the 
COLOR1 register of the TMS340 graphics processor.

frame:	In the case of a noninterlaced display, the screen image output to the 
raster display monitor during a single vertical sweep of the electron beam. In 
the case of an interlaced display, a frame is composed of two fields, each of 
which requires a separate vertical sweep.

frame buffer:	A portion of memory used to buffer rasterized data to be output 
to a CRT display monitor. This term sometimes refers either to a video page or 
to the entire display memory.

frame time:  The time required to display a single frame on a monitor. In the
case of a noninterlaced display, the frame time corresponds to the time 
required to complete a full vertical sweep. This is typically about 1/60 
second.

	G

graphics mode:	A software-controlled configuration of a hardware 
display system to select a specified set of display characteristics such as 
pixel size, screen resolution, monitor-specific video timings, and number of 
video pages. Each display system to which the TMS340 Graphics Library 
has been ported supports one or more graphics modes.

gray scale:	A scale of light intensities ranging from black to white in 
more or less uniform steps.

GSP:	Graphics System Processor. Texas Instruments' TMS340 
Family currently includes two GSPs, the TMS34010 and the TMS34020.

gspcl:	A shell utility program provided with the TMS340 Family Code 
Generation Tools that automatically runs one or more program source files 
through the C compiler, assembler, or linker.

gspl:	A COFF loader utility program provided for use with the 
TMS340 Graphics Library. The utility downloads an executable file from the 
PC to a TMS34010- or TMS34020-based graphics card and executes it.

gun,  electron gun: The element of a cathode-ray tube that emits the electrons
that form the beam that sweeps over the phosphors on the screen. The strength 
of the beam is modulated by the applied signal. In the case of a color monitor, 
the CRT typically contains separate guns to illuminate the red, green, and blue 
phosphors.

	H

halftone:  A process for converting a gray-scale image to black-and-white
patterns of fine dots, the size or density of which in each small region 
corresponds to the intensity level of the original image in that region.

header:	A preamble to a file or data structure that contains information about 
the contents of the file or data structure.

	I

interlaced display:  A raster display in which the displayed image consists of
two fields of scan lines. Odd-numbered scan lines, which make up the odd field, 
are output at one time, and the even-numbered scan lines, which make up the 
even field, are output at another time. The lines of the two fields are 
interlaced on the display to form a single frame or image.

interrupt vector:	A fixed 32-bit location in the TMS340 graphics 
processor's memory that contains the address of a trap or interrupt service 
routine. (Also see trap vector.)

ISR:	Interrupt service routine.

	K

kerning: Font metric; the amount by which a descender (such as the tail of a
lower-case y) extends into the em space of the character to its left. (See em.)

	L

leading: Font metric; the vertical spacing between the bottom of one line of
text (as measured from the lowest descender in the font) to the top of the next 
line of text below it (as measured from the highest ascender in the font).

line-style pattern: A mask of 1s and 0s that are used to control the appearance
of a styled line. As the line is drawn, the mask is rotated one bit per pixel, 
and the rightmost bit in the mask determines whether the next pixel is drawn in 
the foreground or the background color.

loader:	A utility that loads an executable program or code module into a 
processor's memory; the loader typically causes the processor to begin 
executing the program.

long word:   A 32-bit logical word in the TMS340 graphics processor's memory
or a register.

LSB:	Least significant bit. The lowest-order bit in a memory field or 
register.

	M

magic number:	The value contained in a field located at the 
beginning of a file or data structure that identifies the type and revision 
number of the file or data structure.

make utility:	A utility program that automates program development. A make 
utility can update an executable file automatically whenever changes are made 
to one of its source or object files.

monospaced font:   A font in which the character-to-character horizontal
spacing is uniform for all characters.

MSB:	Most significant bit. The highest-order bit in a memory field or 
register.

	O

object file:	A file that has been assembled or linked, and contains machine 
language object code that can be either relocatable or mapped to absolute 
addresses.

OEM:	Original equipment manufacturer. A company that configures 
systems for resale.

off-screen memory:  Frequently used to refer to the portion of the display
memory that is not displayed and is therefore available for other uses, such as 
buffering data. The term is sometimes used to refer to non-display memory 
utilized for similar purposes.

off-screen workspace:	A workspace in memory that has the same width and 
height as the screen but is only 1 bit per pixel.

on-screen memory:   The portion of the display memory that is actually
displayed; the memory comprising the video page or pages.

ordered dither:	A halftoning algorithm, widely used in raster displays, 
that represents intensities as regular dot patterns of varying densities.

outcode: A 4-bit code that represents the position of a point relative to a
rectangular clipping window. Refer to the user's guide for the TMS34010 or 
TMS34020 for details.

outline font:	A computer representation of a font in which each character 
shape is specified as one or more filled regions bounded by curves.

	P

palette:  A digital lookup table used in a computer graphics display to
translate the pixel values from the display memory into the red, green and blue 
components of the pixel as it is displayed.

pattern:  (See area-fill pattern, line-style pattern.)

pen, drawing pen:  A rectangular shape used within the graphics library
to model a physical drawing pen or brush. In tracing the path of a line or 
curve, the area swept out by the pen is filled.

pitch:	The difference in memory addresses from the start of one row of a 
two-dimensional pixel array to the next row of the array. This value is the 
same for each pair of adjacent rows in the array.

PixBlt:	Pixel-aligned block transfer. A PixBlt operation copies a pixel array 
from one location in memory to another. The copy operation may involve 
combining each pair of corresponding source and destination pixels according to 
a Boolean or arithmetic operation. (Also see BitBlt. )

pixel:	 A picture element of a raster display device. 
1) A physical pixel is the smallest individually controllable point of light 
	on a CRT display. 
2) In a bit-mapped display system, a logical pixel is the digital representa-
	tion in memory of the attributes of the physical pixel to be displayed
	at the corresponding location on a CRT display.

pixel array: A two-dimensional array of pixels characterized by a base address
x and y extents, a pitch, and a depth (number of bits per pixel). A pixel array 
with a depth of 1 bit is often referred to as a bit map. A pixel array is 
sometimes referred to as a pixel map or pixmap.

pixel processing:	The merging of a source pixel value with a 
destination pixel value according to a Boolean or arithmetic operation.

pixel-replicated format: The TMS340 graphics processor's architecture requires
that the values loaded into the PMASK (plane mask), COLOR0 (background color), 
and COLOR1 (foreground color) registers be specified in pixel-replicated 
format. In this format, each n-bit pixel is replicated 32/n times through the 
length of the 32-bit register.

pixel size: The length of a logical pixel in bits. Also referred to as the
pixel depth.

plane mask:  A mask that specifies which bits in a pixel are protected from
modification. This mask is the same number of bits in length as a pixel and 
affects all operations on pixels. The graphics library follows the convention 
that a mask bit that is a 1 designates a write-protected pixel bit, while pixel 
bits corresponding to 0s in the plane mask can be modified.

polyline:  A set of connected lines. In the graphics library, a polyline is
specified as a list of points, and a line is drawn between each pair of 
adjacent points in the list.

port:	A device-specific implementation of a software product. All 
device-specific functions of the TMS340 Graphics Library are isolated in a 
small portion of the library software to facilitate the porting of the library 
to TMS34010- and TMS34020-based graphics systems.

proportionally spaced font: A font in which each character is permitted to vary
in width from the others, and the spacing from one character to the next is 
dependent on the width of the character.

	R

raster:	A rectangular grid of picture elements (or pixels) whose colors and 
intensity levels are manipulated to represent images.

raster display:	A display device with a flat surface consisting of a regular, 
two-dimensional grid of picture elements (or pixels), each of which is 
individually addressable.

rasterize: To convert a geometric shape such as a line, curve, or filled region
from its mathematical representation to a set of pixels that represent the 
shape on a raster display. The accuracy of the representation is necessarily 
limited by the resolution of the display.

raster-op: Raster operation. Also referred to as a pixel processing operation.
(See also pixel processing.)

resolution:  The resolution of a raster display device, given in terms of the
number of pixels (or dots) per unit length (measured in inches or millimeters). 
The width and height of a display monitor in pixels is frequently referred to 
informally as the "resolution" of the monitor.

RGB monitor:	Red-green-blue monitor. This is a CRT monitor 
capable of displaying colors, and having separate inputs for the signals that 
drive the red, green, and blue guns of the CRT.

run-length encoding:	An image-compression technique that encodes each
scan line of an image as a series of color transitions. The color for each 
transition is paired with the number of pixels in the run prior to the next
color transition.

	S

scan line: A horizontal line output to a raster scan display. The term is also
used to refer to a row of logical pixels in memory that are to be output to a 
particular scan line of the display.

screen coordinate system:  The x-y coordinate system in which the absolute
position of the pixels on the screen are specified. The screen origin is fixed 
in the top left corner of the screen. The x coordinates increase from left to 
right, and y coordinates from top to bottom.

screen origin:	The x-y origin at the top left corner of the screen, which 
serves as an absolute reference point for referring to pixels on the screen.
screen refresh:	The operation of streaming the contents of the display memory 
to the monitor in synchronization with the sweep of the electron beam. In a 
video RAM system, a screen-refresh cycle typically occurs during the horizontal 
blanking interval that precedes each active scan line to download the logical 
pixels in the scan line to the video RAMs' serial registers.

SDB:	Software Development Board. Texas Instruments provides SDBs for
developing software to run on TMS34010- and TMS34020-based systems.

seed fill:	A fill operation that fills a connected region of pixels on the 
screen with a solid color or pattern, beginning at a specified seed pixel. All 
pixels that are part of the connected region that includes the seed pixel are 
filled.

serial register: A register within a video RAM device that contains the data
corresponding to a row in memory that is output from the serial port to refresh 
the screen. The data in the register may be serially clocked out at a rate 
independent of activity at the video RAM's random-access port.

source file:	An ASCII text file that contains either C language or TMS340x0 
assembly language source code that can be compiled or assembled to generate an 
object file.

stroke font:	A computer representation of a font in which each character 
shape is specified as a series of line segments (or strokes).

styled line:	A rasterized line that is drawn with a line-style pattern. 
Bresenham's algorithm is used to select a thin, but connected, set of pixels to 
represent the line. The color of each pixel in the set is governed by the 
corresponding bit in the line-style pattern. (See line-style pattern.)

symbolic debugger: A debugger utility with the capability of utilizing symbolic
information retained during the compilation and linking processes.

system font:	The graphics library's default font. This font is permanently 
installed as font 0 and is always a block font.

	T

TDB:	TMS34010 TIGA Development Board. This TMS34010-based PC add-in
card from Texas Instruments contains a TMS34092 VGA Interface Chip, and drives 
analog RGB monitors at resolutions of 640y480 and 1024y768, and pixel sizes of 
1, 2, 4, and 8 bits.

TIGA, TIGA-340:	Texas Instruments Graphics Architecture. A combined software 
and hardware standard for graphics systems defined by TI. TIGA is a standard 
approach to managing communications between the PC host and the TMS340 graphics 
processor. At the core of TIGA is an interprocessor communications protocol 
that links an application or environment driver to a library of graphics 
functions that execute on the TMS340 processor.

TMS340:	Product name for a family of graphics system processors and peripherals 
manufactured by Texas Instruments.

TMS34010:	First-generation graphics system processor.

TMS34020:	Second-generation graphics system processor.

TMS34070:	A low-cost color palette device supporting displays with 4 bits 
per  pixel.

TMS34082:	Floating-point coprocessor that interfaces directly to the 
TMS34020   graphics processor.

TMS34092: TI's VGA Interface Chip. The TMS34092 is a memory and pixel pipeline
peripheral for low-cost PC video adapters using the TMS34010. VGA pass-through 
capability is provided.

transparency: A pixel attribute which, when enabled, permits objects written to
the screen to have transparent regions through which the original background 
pixels are preserved. Transparency is useful in graphics applications involving 
text, area-fill patterns, and pixel arrays in which only the shapes, and not 
the extraneous pixels surrounding them, are drawn to the screen.

trap vector:	A fixed 32-bit location in the TMS340 graphics processor's 
memory that contains the address of a trap or interrupt service routine.
(Also see interrupt vector.)

typeface, face:	A collection of fonts that have common features such as style 
and weight, but which differ in size.

	V

VGA:	Video Graphics Array. A display adapter from IBM.

video page: The portion of display memory that contains an image that can be
output to the monitor screen or other display surface.

video RAM, VRAM: Video random-access memory. A dual-ported dynamic memory
device for computer graphics applications. One interface supports random read 
and write accesses to the memory; the other interface provides an independently 
clocked serial data stream to refresh a display.

	W

word:	A 16-bit logical word in GSP memory or a register.

workspace:	(See off-screen workspace.)

	X

XDS System:	Extended Development Support System. Texas Instruments' XDS 
in-circuit emulation systems support the development of TMS34010- and 
TMS34020-based systems.

	Z

zoom:	To scale an image so that it is either magnified or reduced in size.

