CRTs, flat-panel, and specialty monitors

§          Distributed processing separates the data processing onto different servers rather than on one dedicated host computer

a)    Cathode-Ray Tube

§          Most common type of desktop monitor.

§          Uses similar technology as standard TV screens

§          Advantage is they are relatively inexpensive and have a high quality image display.

§          Disadvantage is they take up a lot of room

b)    Flat-Panel Monitor

§          The advantage is they take up less room, and are frequently used on laptop computers.  Now becoming popular for desktops as well since they have dropped in price

§          Two basic types are:

§          Passive matrix (dual scan monitors): lower power, but poorer clarity

§          Active matrix (TFT: Thin Film Transistor): costs more, uses more power, but produces a much better image.

c)     Other (Specialty) Monitors

§          E-books (aka e-book readers) are PDA sized devices that display text and graphics.  These have not had a lot of commercial success, yet it is possible to download e-books onto computers.

§          Data projectors: capable of projecting the output onto a screen for a large audience

§          High Definition TeleVision (HDTV): a merger of microcomputers and television (PC/TV) offers much clearer and more detailed wide screen pictures than a standard TV (but currently at more cost).  Since images are digital, they can be stored and edited.

output

Output is processed data or information

It typically takes the form of text, graphics, photos, audio, or video

Output devices are any hardware used to provide or create output from the computer, e.g. printers, monitors, speakers, etc.

About   resolution, dot pitch, refresh rate, and size.

§          Clarity: the quality and sharpness of a monitor; depends on:

§          Resolution: measured in Pixels (Picture Elements) e.g. a 1,280 x 1,024 resolution screen displays 1,310,720 pixels.  The greater the number of pixels, the better the resolution.

§          Dot Pitch: the distance between pixels, typically measured in millimeters.  Most monitors have a dot pitch less than 0.3 mm.  The smaller the dot pitch, the better the clarity.

§          Refresh Rate: how often the image is “re-drawn” on the monitor.  Most monitors have a refresh rate of 75 Hz or better (image refreshes 75 times every second).  The faster the rate, the better the image

§          Size or Viewable Size: the diagonal length of the monitor’s viewing area.  Smaller monitors have better image quality, but it’s also smaller to view

voice recognition systems

a)    Voice recognition systems

§          Voice Recognition Systems use a microphone for input, and a special sound card and software translates the analog signals into digital signals that can be processed and stored.

§          Many applications now support voice recognitions.

§          Using a “language bar” you can switch between “voice command mode” – allowing you to control menu options, and “dictation mode” – allowing you to enter content text into a document.

b)    MIDI

§          Musical Interface Digital Interface (MIDI) is a standard that allows musical instruments to connect to a computer.

§          MIDI devices are specialized musical instruments that provide input in the form of encoded digital signals representing musical sounds.

§          Electronic keyboards are the most commonly used MIDI devices.

difference between digital cameras and traditional cameras

§          Digital cameras store the images electronically

§          Traditional cameras use film

pointing and scanning devices different

§          A pointing device just changes your location on the screen (moves the cursor).  A scanning device converts printed output into digital input for processing by the computer.

   three types of scanners.

§          Scanning devices convert scanned text and images into a form that the system unit can process.

a)    Optical Scanners

§          An optical scanner (aka scanner) accepts documents consisting of text and/or images and converts them to machine readable form.

§          They work by recognizing light, dark, and colored areas that make up individual letters or images.

§          Flatbed scanner: works like a copy machine

§          Portable scanner: often is a hand held device that slides across the document being scanned.

§          Typical use is by advertising professionals who scan images and combine them with text.

b)    Bar Code Readers

§          Bar code readers/scanners contain photoelectric cells that read bar codes.

§          Typical uses are in grocery stores that use Universal Product Codes (UPC) which match up the product with a database entry containing product information such as price.

§          These devices are either handheld wand readers or platform scanners.

c)     Character and Mark Recognition Devices

§          These devices read special characters and marks.

§          Three types include:

o       Magnetic Ink Character Recognition (MICR): used by banks for processing checks.  Special reader/sorter machines process the checks much faster than the older manual methods

o       Optical Character Recognition (OCR): use special pre-printed characters that can be read by a light source, and are still understandable by human readers.  Retail stores frequently used these types of scanners.

o       Optical Mark Recognition (OMR) aka Mark Sensing: frequently used to score multiple choice tests marked by pencil on a form.

pointing device

§          A pointing device provides a comfortable interface with the system unit, by accepting pointing gestures and converting them into machine-readable input.

§          Five types include:

a)    Mouse

§          A mouse controls the pointer displayed on the monitor

§          The mouse pointer usually appears in the shape of an arrow

§          Mechanical mouse: traditional mouse with a ball in the bottom and cord connecting it to the computer

§          Optical mouse: has no moving parts – it emits and senses light to detect mouse movement.

§          Cordless or wireless mouse: a battery operated device that typically uses radio waves or infrared light waves to communicate with the system.

§          Other similar pointing devices include:

§          Trackball (aka Roller Ball)

§          Touch surfaces (aka Touch Pads)

§          Pointing stick (aka Trak Point)

b)    Joystick

§          Most popular input device for computer games

c)     Touch Screen

§          Monitor with a touch sensitive plastic screen

§          Typically used for restaurants, ATM’s and information kiosks

d)    Light Pen

§          A light sensitive pen-like device

§          Typically used for editing digital images.

§          They can include both wired and wireless technologies

e)     Stylus

§          A pen-like device commonly used with Tablet PCs or PDAs

§          Require a touch sensitive input device such as a writing pad

§          Typically used for entering menu choices or text via handwriting.

About keyboards

five common types of keyboard designs.

§          Traditional keyboards: full-sized, rigid, rectangular keyboards that include function, navigational, and numeric keys.

§          Flexible keyboards: fold or roll up for easy packing and storage for mobile users.

§          Ergonomic keyboards: similar to traditional, but designed to specifically alleviate wrist strain associated with repetitive movements of typing.

§          Wireless keyboards: more expensive than traditional keyboards, but give the flexibility of un-tethering the cord.

§          PDA keyboards: miniature keyboards for PDAs for sending email, etc

some common keyboard features

• Numeric keypads: easier entry of numbers and arithmetic symbols
• Toggle keys: on off keys for such things as <Caps Lock> and <Scroll Lock>
• Combination keys: perform an action when combined with other keys, e.g. <Ctrl> key or <Alt> key

What is input? What are input devices?

§          Input is any data or instructions that are used by a computer.  They come from an end user, and must be translated into digital codes that the computer can process.

§          Input devices are hardware used to translate words, sounds, images, and actions that end users produce into a digital format the computer can process.

§          Examples of input devices include keyboards, a mouse, a microphone, etc.