Measures of Central Tendency: Mean, Median and Mode
COMPUTER GRAPHICS-UNIT-I
1. UNIT - I
❖Video display devices
❖Raster scan systems
❖Random scan systems
❖Graphics monitors and workstations
❖Input devices
❖Hardcopy devices
❖Graphics software
2. VIDEO DISPLAY DEVICES
❖The display devices are known as output devices. The most commonly used
output device in a graphics video monitor. The operations of most video monitors are
based on the standard cathode-ray-tube (CRT) design.
❖Properties of video display devices are persistence, resolution, and aspect ratio.
❖Computer Graphics has become a common element in today's modern world. Be it in user
interfaces, or data visualization, motion pictures etc., computer graphics plays an important
role. The primary output device in a graphics system is a video monitor.
3. REFRESH CATHODE RAY TUBES
❖ A beam of Cathode rays discharged by an Electron gun moves through some deflection
systems. So these deflection systems which direct the beam towards a described specified position
on the Screen.
❖ The primary output device in a graphics system is a video monitor. The operation of most
video monitors is based on the standard cathode ray tube (CRT) design.
❖ The inner side of the screen is coated with phosphor substance which gives off light when it is
stroked by electrons. It is possible to control the point at which the electron beam strikes the
screen, and therefore the position of the dot upon the screen, by deflecting the electron beam.
5. RASTER SCAN SYSTEMS
❖A raster scan, or raster scanning, is the rectangular pattern of image capture and
reconstruction in television. By analogy, the term is used for raster graphics, the pattern of
image storage and transmission used in most computer bitmap image systems.
❖In addition to the central processing unit (CPU), a special processor, called the video
controller or display controller, is used to control the operation of the display device.
❖ Simple Organization of the Video Controller • Two registers are used to store the
coordinates of the screen pixels.
7. VIDEO CONTROLLER
❖Display Controller controls the operation of the display device. It is also called a video
controller.
❖Working : The video controller in the output circuitry generates the horizontal and vertical
drive signals so that the monitor can sweep. Its beam across the screen during raster scans.
❖Architecture. In a Raster scan display, the image which has to be displayed is saved in a
binary format (0s and 1s) in the refresh buffer memory. Then, a video controller is used to scan
each and every line of the Refresh Buffer Memory.
9. RANDOM SCAN SYSTEMS
❖In Random-Scan Display electron beam is directed only to the ares of screen where a picture has to be
drawn. It is also called vector displays, as it draws picture one line at time. It can draw and refresh component
lines of a picture in any specified sequence. Pen plotter is an example of random-scan displays.
❖Random-Scan Display Processors:
Input in the form of an application program is stored in the system memory along with graphics package.
Graphics package translates the graphic commands in application program into a display file stored in system
memory. This display file is then accessed by the display processor to refresh the screen. The display processor
cycles through each command in the display file program. Sometimes the display processor in a random-scan is
referred as Display Processing Unit / Graphics Controller.
11. GRAPHICS MONITORS AND WORK STATIONS
❖Graphics monitors can be used in personal computers to do normal day to day task, like displaying a
document or a movie or browsing internet.
❖Graphics monitors can be used for reverse car camera display systems, or CCTV camera monitoring
systems.
❖Workstations are also used for medical imaging, simulation systems, etc.
❖The current workstation market uses x86-64 microprocessors. Operating systems available for these
platforms include Microsoft Windows, FreeBSD, various GNU/Linux distributions, Apple macOS(formerly
known as OS X), and Oracle Solaris. Some vendors also market commodity mono-socket systems as
workstations.
13. INPUT DEVICES
❖In computing, an input device is a piece of computer hardware equipment used .
❖Input devices connected to a computer system allow the user to enter data or interact with running
programs, and are used for activities ranging from editing computer programs to playing videogames
(q.v.).
❖Input devices can be separated into five classes: keyboards, locators, picks, valuators, and buttons.
❖Following are some of the important input devices which are used in a computer − ... Keyboard;
Mouse; Joy Stick; Light pen; Track Ball; Scanner; Graphic Tablet; Microphone ...
15. HARD COPY DEVICES
❖Hardcopy Devices provides a technical summary of computer output hardcopy devices
such as plotters, computer output printers, and CRT generated hardcopy.
❖Important related technical areas such as papers, ribbons and inks, colour techniques,
controllers, and character fonts are also covered.
❖An output device is any piece of computer hardware equipment which converts
information into human-readable form.
17. GRAPHICS SOFTWARE
❖In computer graphics, graphics software refers to a program or collection of programs that enable
a person to manipulate images or models visually on a computer.
❖There are animation and video editing software. Different types of software are often designed to
edit different types of graphics such as video, photos, and vector-based drawings. The exact sources
of graphics may vary for different tasks, but most can read and write files.
❖Coordinates are always specified relative to an ordered basis. Bases and their associated
coordinate representations let one realize vector spacesand linear transformations concretely
as column vectors, row vectors, and matrices, hence are useful in calculations.
