Chapter 7 Input/output

Chapter 7 Input/output     

In computing, input/output, or I/O, refers to the communication between an information processing system (such as a computer), and the outside world, possibly a human, or another information processing system. Inputs are the signals or data received by the system, and outputs are the signals or data sent from it. The term can also be used as part of an action; to "perform I/O" is to perform an input or output operation. I/O devices are used by a person (or other system) to communicate with a computer. For instance, a keyboard or a mouse may be an input device for a computer, while monitors and printers are considered output devices for a computer. Devices for communication between computers, such as modems and network cards, typically serve for both input and output.

Interface

  I/O Interface is required whenever the I/O device is driven by the processor. The interface must have necessary logic to interpret the device address generated by the processor. Handshaking should be implemented by the interface using appropriate commands like (BUSY,READY,WAIT), and the processor can communicate with I/O device through the interface. If different data formats are being exchanged, the interface must be able to convert serial data to parallel form and vice-versa. There must be provision for generating interrupts and the corresponding type numbers for further processing by the processor if required
A computer that uses memory-mapped I/O accesses hardware by reading and writing to specific memory locations, using the same assembly language instructions that computer would normally use to access memory.

Direct addressing

In this type of address of the data is a part of the instructions itself. When the processor interprets the instruction, it gets the memory address from where it can be read/written the required information. For example

Keyboard Entry

•    Keyboards

–    Traditional keyboards

–    Ergonomic keyboards

–    Wireless keyboards

–    PDA keyboards

–    Virtual keyboards

•    Features

–    Typewriter keyboard with numeric
keypad

–    Special purpose keys

•    Toggle and combination keys

Pointing Devices

•    Mice

–    Mechanical

–    Optical

–    Cordless                                                                                          or wireless

•    Three similar devices to mice

–    Trackball

–    Touch pads

–    Pointing stick

Scanning Devices

•    Scanners  move across text and images

•    Scanning devices convert scanned data into a form the system unit can process

•    Types

•    Optical – known as a scanner

•    Recognizes light, dark, and colored areas that make up individual letters or images

•    Types

•    Flatbed – much like a copy machine

•    Portable – typically a handheld device that slides across the image making direct contact

•    Document – similar to flatbed except that it can quickly scan multipage documents; automatically feeds one page of a document at a time

•    Card Readers interpret encoded information that is stored on debit, credit, and identification cards

•    Types

•    Magnetic card reader (Key Term) – information is stored on a thin magnetic strip on the back of a card; is read when swiped through a card reader

•    Radio frequency card reader – not as common but more convenient; card has a RFID (radio frequency identification) (Key Term) chip that is read when passed within a few inches of a card reader

Image Capturing Devices

•    Digital cameras

–    Images recorded digitally on a disk

–    Images can be downloaded to a computer

•    Digital video cameras

–    Records motion digitally

–    Can take still images as well

–    WebCams

•    Specialized digital video cameras

•    Broadcast
images over the
Internet

Audio-Input Devices

•    Audio input can take many forms, including the human voice and music

•    Convert speech into digital code; most common device is the microphone; gaining in popularity are the portable digital voice recorders used with voice recognition systems

•    Voice recognition systems

•    Microphone, bundled with sound card and software

•    Some voice recognition systems must be trained for user’s voice

•    Some can translate from one language to another

Monitors

•    Known as screens or display screens

•    Output referred to as soft copy

•    Features

–    Resolution/pixels

–    Dot pitch

–    Refresh rate

–    Size

•    Cathode-ray tube (CRT) monitors

•    Flat-panel monitors

–    Require less power to operate

–    Portable and thinner than CRTs

•    Other monitors

–    E-books readers

–    Data projectors

–    High-definition television (HDTV)

Printers

•    Three major types of printers:  ink-jet, laser, and thermal; most people are familiar with these

•    Inkjet printers spray ink at high speed onto the surface of paper

•    Laser printers uses a laser light beam to produce images

•    More expensive than ink jet printers

•    Thermal printers – uses heat elements to produce images on heat sensitive paper

•    Used to produce high quality art work

•    Other Printers

•    Dot-matrix – slow and not used much any more; poor quality but faster than some of newer printers

•    Very noisy

•    Inexpensive

•    Plotters – special purpose for maps, images, architectural & engineering drawings

•    Photo printers – designed to print photographs from digital cameras

•    Portable printers – usually small/lightweight and designed to work with a notebook computers; may be ink-jet or laser printer that prints in either b/w or color

Combination Input and Output Devices

•    Combination devices  include fax machines also known as a facsimile (fax) transmission machine, multifunction devices, Internet telephones, and terminals

•    Multifunction devices (MFD), can combine the capabilities of a scanner, printer, fax and copy machine

•    Internet telephone – specialized input and output devices for receiving and sending voice communication

•    Telephony (Key Term) – the transmission of telephone calls over computer networks

•    Known as Voice over IP (VoIP) (Key Term)

•    Uses Internet rather than traditional phone system

Careers In IT

•    Technical writers prepare instruction manuals,   technical reports, and other scientific or technical documents

•    Typically requires a college degree

–    Communications

–    Journalism

–    English

–    Specialization or familiarization with a technical field

A Look to the Future

•          Wearable computers

•          Send and receive email while jogging

•          Maintain your personal schedule book

•          Remember the names of people at a party