14. Computer Systems Output Devices

What Is Output? Data that has been processed into useful form called information Text Graphics Audio Video

What Are Output Devices? Any computer component capable of conveying information to a user Display devices Printers Other display devices Data projectors Fax machine Multifunction devices Terminals

Display Devices An output device that visually conveys text, graphics, and video information CRT Monitors Screen housed in a plastic or metal case Cathode ray tube (CRT) Picture elements (Pixels) Viewable size 17” monitor  15.7” viewable size Colour vs. monochrome monitor Colour monitor and colour depth Monochrome monitor and gray scaling

Display Devices Flat-panel displays LCD displays Lightweight Used by handheld computers, digital watches, calculators Active (TFT) and passive-matrix displays Number of transistors Cost, sharpness and clarity of images Also used with desktop computers with space and weight constraints

Display Devices Flat-panel displays Gas plasma Large displays of up to 42” of viewable area Gas glows that produce pixels that form an image Higher display quality More expensive

Display Devices Factors that affect monitor quality Resolution Related to the number of pixels it can display Higher resolution Increased sharpness Smaller images Number of columns of pixels X number of rows of pixels Dot pitch Vertical distance between each pixel on a monitor Measure of image clarity The smaller the distance between each pixel, the sharper the image

Display Devices Factors that affect monitor quality Refresh rate Speed that the monitor redraws images on the screen Measured in Hertz (Hz) to measure flicker The higher the refresh rate, the lower the flicker Interlacing Old method of refreshing images

Display Devices Video Cards Graphics card, video adapter Converts digital output into an analog video signal that is sent through a cable to a monitor Number of colours  number of bits used to store information about each pixel 8-bit card (2 8 colours = 256 colours) 24-bit card (2 24 colours = 16.7 million colours) Video RAM Memory to generate the resolution and number of colours you want to display

Display Devices Monitor Ergonomics Incorporate comfort, efficiency and safety into the design of items in the workplace Digital controls help fine-tune the display Tilt-and-swivel base to minimise neck strain and reduce glare MPR II standard regarding electromagnetic radiation (EMR) ENERGY STAR program to create energy-efficient monitors

Display Devices High-Definition Television Uses digital television signals Can be used as a monitor while browsing the Internet Monitor come TV HDTV

Printers An output device that produces text and graphics on a physical medium such as paper or transparency film Hard copy (printout) vs. softcopy (monitor) Portrait vs. landscape Printing requirements vary

Printers Impact Printers Printing mechanism strikes paper, ribbon and character together Near letter quality (NLQ) Used for multipart forms strikes through multiple layers of paper

Printers Impact Printers Dot matrix printers Small dots form characters Continuous form paper More pins on print head means higher quality Speed measured in characters per second (cps)

Printers Impact Printers Line printers High speed Prints an entire line at a time Band printer Shuttle-matrix printer

Printers Non-impact Printers No mechanism strikes the paper Much quieter than impact printers Ink-jet printers Spray tiny drops of ink onto the paper Both black-and-white and colour Resolution measured in dots per inch (dpi) Speed measured in pages per minute (ppm) Nozzles spray ink

Printers Non-impact Printers Laser printers High-speed, high-quality non-impact printer Very high quality resolution - 300dpi to 1,200 dpi Stores entire page before printing it Page description language (PDL) PCL (Printer Control Language) Postscript Operates much like a copy machine Toner Replace cartridge

Printers Non-impact Printers Thermal printers Pushes electrically heated pins against heat-sensitive paper Thermal transfer printer Print head heats and melts the ink of the ink ribbon to print the dot-composed character on normal paper

Printers Non-impact Printers Portable printers Small, lightweight printer that allows a mobile user to print from a laptop or handheld computer while traveling Ink-jet Thermal Parallel port or infrared port

Printers Non-impact Printers Plotters and Large-Format Printers Used for high-quality drawings such as blueprints, maps, circuit diagrams, and signs Plotters Pen plotters Electrostatic plotters Large-format printer Photo-realistic quality color prints

Printers Non-impact Printers Special-purpose printers Snapshot printer Photo lab quality pictures Label printer

Audio Output Audio output devices Produce music, speech, or other sounds Speakers Low-quality sound For high quality sound Stereo speakers and woofer Sound card Headsets

Other Output Devices Data projectors Allows an audience to view output LCD projectors Digital light processing (DLP) projector Facsimile (Fax) Machine Used to transmit and receive an image of a document over a phone line Stand-alone Fax modem Designed to transmit documents to a fax machine or to another fax modem

Other Output Devices Multifunction Devices Can print, scan, copy, and fax Less space Lower cost than separate units For example, OfficeJet by Hewlett-Packard is a colour printer, scanner and photocopier all in one device

Terminals Performs both input and output Monitor Keyboard Video card Dumb terminal Intelligent (programmable) terminal Modern PC Point-of-sale (POS) terminal Automatic teller machine (ATM)

Output Devices For Physically Challenged Users Issues with output devices Cannot see graphics because of visual impairments Cannot hear audio because of hearing impairment Possible solutions Windows Accessibility Properties dialog box Braille printer

Output Devices For Physically Challenged Users

Computer Types and Architectural Characteristics Personal computer (PC) Workstation General-purpose computer Supercomputer Microcomputer Process control computer

Personal Computer Desktop Meant to be placed on a desktop Laptop Portable computer which is slightly larger and heavier than a notebook computer Notebook A lightweight thin portable computer.

Workstation More powerful than the personal computers Main applications are Research and development fields Complex scientific and engineering calculations Product manufacturing fields Used in CAD, CAM, etc application. Software development field Computer Aided Software Engineering tool Communication network field Client machines or server machines in distributed processing system.

Supercomputer Capable of performing complex and large calculations at extremely high speed Main use Weather forecast Simulation of nuclear power generation Orbit calculation of artificial satellites

Supercomputer Fujitsu VPP700E: 256 Fujitsu CMOS processing elements

Microcomputer A small computer with a microprocessor Used in household appliances Control data is recorded in ROM Output devices are called actuators Motors or switches

Process Control Computer Computers that control machines in heavy industries Machines entirely automated through process control computers Used in general building security system, highway traffic control, etc.

General Purpose Computer (Mainframe) A very large and powerful computer capable of supporting thousands of users simultaneously. Mainframes are just below supercomputers in processing power

14. Computer Systems Output Devices

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14. Computer Systems Output Devices