Input
and Output
Data Given, Information Received
- Keyboard is the most popular input device.
- Usually similar to a typewriter's keyboard.
- Data entry operators enter large amounts of data into computers
via keyboards.
- Originally popularized by the Macintosh computer, now used
on all GUIs.
- It operates via a ball underneath that is rolled on a flat
surface.
- MS Windows displays small pictorial symbols called icons,
that represent directories of files, files, or applications.
- Clicking once on an icon selects it, double-clicking an application
icon launches it.
- A variation of the mouse, with the ball on top, is called
a trackball.
- The use of special equipment to collect data at the source
and send it directly to the computer.
- Magnetic-Ink Character Recognition (MICR)
- Optical Recognition
- Optical Mark Recognition (OMR)
- Optical Character Recognition (OCR)
- Handwritten Characters
- Bar Codes
- Method of machine-reading characters made by magnetized particles.
- Most common example is numbers on the bottom of personal checks.
- Checks are read by MICR reader/sorter.
- Written by MICR inscriber machines.
- A machine senses pencil marks on paper.
- Used mostly in grading checked boxes on tests.
- OMR uses a light beam to recognize the marks and convert them
to electrical signals that are sent to the computer for processing.
- Uses a light source to read characters and convert them into
electrical signals to be sent to the computer for processing.
- A standard typeface, OCR-A is often used by wand readers connected
to point of sale (POS) terminals.
- Newer OCR software works with desktop and hand-held scanners
and fax-modems and can read many fonts.
- Can be read by some machines that have special rules for capturing
data and processing it.
- Must follow specific rules for formatting characters.
- Unique patterns of stripes printed on commercial products
to identify them.
- A bar code reader reads the stripes by means of reflected
light.
- Standardized by the Universal Product Code (UPC), used mainly
in supermarkets.
- Allows for faster, more accurate checkout
- Inventory control and marketing information
- Process of presenting input data to the computer through the
spoken word.
- Speech recognition devices accept spoken words through a microphone
and convert them into digital code the computer can understand.
- Usually require users to train the systems to recognize their
spoken words.
- Most CRT screens use raster-scan technology,
in which a beam of electrons is sent to the screen, causing the
phosphor coated screen to emit light, forming an image.
- Bit-mapped displays divide the screen into individually addressed
dots or pixels.
- The screen resolution is measured by the number of vertical
and horizontal pixels (the more pixels, the higher the resolution).
- 640 X 480
- 800 X 600
- 1,024 X 768
- 1,280 X 1,024
- Thinner and lighter than CRTs, making them popular on portable
computers.
- Most common flat-panel display is the liquid crystal display
(LCD).
- Thin-film-transistor (TFT) active matrix screens, in which
each pixel is powered by its own transistor, are becoming more
popular.
- Terminals consist of an input device, an output device, and
a communications link to a main computer.
- A terminal with its own screen is called a video display terminal
(VDT).
- Dumb terminals are merely a means of entering
data into and receiving output from a computer. They have no CPU
or secondary storage.
- Smart terminals can do some limited processing.
- Intelligent terminals can be programmed to perform a variety
of processing functions.
- There are two principal ways of classifying printers:
- Impact printers form their characters by physically
striking the paper.
- Nonimpact printers use a noncontact printing
method.
- Dot-matrix printers
- Inexpensive printers that produce output by striking a ribbon
with groups of pins arranged in a vertical line.
- 24 pin printers produce output at "near-letter quality"
- Daisy-wheel Printer
- Features characters on a removable wheel, noted for high-quality
printing.
- Line Printers
- Print entire line at a time.
- Common on mainframes.
- Laser Printers
- Use a laser beam to transfer images to paper.
- Print a page at a time.
- Produce high quality output.
- Becoming very popular as prices come down.
- Ink-Jet Printers
- Spray ink onto paper from jet nozzles.
- Quality approaches laser output.
- Can use several different colors of ink, producing very good
color graphics.
- Requires speech synthesis, the process of enabling machines
to talk.
- Machine voices are the product of voice synthesizers.