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An overview of various input and output devices used in computing systems. It covers keyboards, pointing devices such as mice and touch screens, scanners, and display devices like crt monitors and flat-panel displays. The functions, types, and advantages of each device, making it useful for students and professionals in computer science and related fields.
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Keyboard: input device containing keys, arranged in a typewriter configuration, used to input letters, numbers, and other symbols Standard alphanumeric keys (letters and numbers) Numeric keypad Function keys Directional and special keys
Standard configuration is QWERTY, to match typewriter Dvorak is another configuration
Can be:
Wireless Portable Foldable
Handheld PCs and mobile devices today often have a mini keyboard or thumb pad
Electronic pen (stylus or digital pen): used instead of a mouse to select objects, as well as to draw or write electronically on the screen
Commonly used with pen-based PCs To issue commands and input data If handwriting recognition is used, written text can be converted to editable typed text
Also used with Digital writing systems Graphics tablets Signature capture devices
Touch screen: display device that is touched with the finger to issue commands or make selections
Touch screen kiosks used in retail stores, movie theaters, airports, etc., and point-of-sale (POS) systems
Scanner (optical scanner): reads printed text and graphics and converts them to digital form
Can scan photos, photo negatives, documents, drawings, etc.
Input usually is a single printed image
Output depends on type of scanner:
An image file (GIF or JPG) saved to disk Text that can be used in word processor Display of a number
Quality of scanned images depends on optical resolution, measured in number of dots per inch (dpi). 1 dot = 1 image pixel.
Good flatbed scanner has 3200 dpi or more
The higher the resolution, the better the image quality but the larger the file size.
Scanned film negatives and slides have resolution equal to or better than digital cameras
Resolution demo
Barcode: machine-readable code that represents data as a set of bars
Reader displays code corresponding to barcode
Universal Product Code (UPC)
Barcode used in supermarkets
Code 39 Barcode used for products in general
POSTNET code
Barcode used by USPS
Optical mark reader (OMR): reads data from special forms to score exams, questionnaires, ballots, etc.
Use pencil to fill in small circles/shapes on the form to indicate their selections
Optical character recognition (OCR) reader: scans text and converts to ASCII characters
Used for:
Turnaround documents, such as monthly bills To get text from a scanned document, for importing into a word processor
Magnetic ink character recognition (MICR) reader: reads MICR characters on bank checks
Used to process every bank check
Digital camera: takes pictures and records them on digital media instead of film
Still cameras take individual photos
Consumer ("point and shoot") and professional versions
Video cameras capture moving video images
Available in a wide variety of sizes and capabilities
Images are immediately available
Typically use flash memory as storage media
Photos can be transferred to a PC or printer, posted to a Web page, burned onto a CD or DVD, and edited with software
Camera resolution is measured in megapixels
Maximum number of pixels in an image, .e.g., 2000 pixels wide by 1000 pixels high = 2 megapixels
Each pixel limited to 8 (at most 12) bits of color
Digital camcorder: similar to analog camcorders, but stores images on digital media
Media usually is mini digital video (DV) tape cartridges or rewritable DVDs
PC video camera (PC cams, Web cam): transmits video images over the Internet, such as during a videoconference or video phone call Poor picture quality but good enough for its purpose
Voice record demo Speech demo
Display device: output device that presents output visually Monitor: standalone display device for desktop PC Display screen: screen built into the unit of all-in-one PCs, notebook computers, handheld PCs, smart phones, consumer devices, and many other devices
CRT monitor: projects images onto a display screen using same technology as older TVs Beam of electrons scans the screen
Flat-panel display: forms images by manipulating electronically charged chemicals or gases sandwiched between panes of glass
Connects display device to computer and controls video display
May be on motherboard or adapter card
Usually provides several user-selectable resolutions
Has own RAM The more RAM, the faster images can be displayed
Has monitor port for CRT device and DVI port for flat panel device
Impact:
Print head strikes the paper, much like a typewriter (dot matrix printer) Very low cost per page but noisy and poor print quality Now used for multipart forms and shipping documents
Non-impact
Ink jet Laser The most common for home and business
Whether prints in color or black-and white only
Whether personal or network printer
Quality is called print resolution and measured in dots per inch (dpi)
Not the same as monitor or digital camera resolution; not dots per page
Print speed is measured in pages per minute (ppm)
Uses toner powder and technology similar to that of a photocopier to produce images on paper
The standard for business documents
Has its own RAM, the more the better
Print one entire page at a time Must have enough RAM for page
Usually black and white, though can get color
Common print resolution is 600 to 2,400 dpi
Low cost per page, excellent print quality, high ppm
