WIRELESS COMMUNICATION

WIRELESS COMMUNICATION

System using radio-frequency, infrared, microwave, or other types of electromagnetic or acoustic waves in place of wires, cables, or fibre optics to transmit signals or data.

WIRELESS COMMUNICATION

Wireless devices include cell phones, two-way radios, remote garage-door openers, television remote controls, and GPS receivers (see Global Positioning System). Wireless modems, microwave transmitters, and satellites make it possible to access the Internet from anywhere in the world. A Wireless Markup Language (WML) based on XML is intended for use in such narrow-band devices as cellular phones and pagers for the transfer and display of text.

Basic computer components

components

Input devices      Keyboard · 
                          Image scanner ·
                          Microphone ·
                          Pointing device (Graphics tablet  · Joystick · Light pen · Mouse ·                                                    Touchpad ·    Touchscreen   · Trackball)

                         · Webcam (Softcam)

Output devices    Monitor
                         · Printer
                         · Speakers

Removable data storage Optical disc drive (CD-RW · DVD+RW)
                                                                 · Floppy disk
                                                                  · Memory card
                                                                  · USB flash drive

Computer case Central processing unit (CPU) · Hard disk
                                                                        Solid-state drive ·
                                                                        Motherboard ·
                                                                        Network interface controller ·
                                                                        Power supply ·
                                                                        Random-access memory (RAM) ·
                                                                        Sound card ·
                                                                        Video card

Data ports Ethernet · Firewire (IEEE 1394) · Parallel port ·
                                                                    Serial port · 
                                                                    Universal Serial Bus (USB)

Output Device

O.D
An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by an information processing system (such as a computer) to the outside world.
In computing, input/output, or I/O, refers to the communication between an information processing system (such as a computer), and the outside world. Inputs are the signals or data sent to the system, and outputs are the signals or data sent by the system to the outside.

Examples of output devices:
Speakers
Headphones
Screen (Monitor)
Printer

Computer Science

• Computer Science

                computer-charles babage
                
                 Basic Computer Components
         
                 memory device

                 Input devices
         
                 Output Devices

• Software
• Hardware
• Languages              
• Internet
• Wireless Communication

Super Computer
 

Input Devices

Input devices

Despite the development of alternative input devices, such as the mouse, touchscreen, pen devices, character recognition and voice recognition, the keyboard remains the most commonly used and most versatile device used for direct (human) input into computers.

 Mouse

Hand-controlled electromechanical device for interacting with a digital computer that has a graphical user interface.

 The mouse can be moved around on a flat surface to control the movement of a cursor on the computer display screen. Equipped with one or more buttons, it can be used to select text, activate programs, or move items around the screen by quickly pressing and releasing one of the buttons (“clicking”) or by keeping a button depressed while moving the device (“clicking and dragging”).

Keyboard

In computing, a keyboard is a typewriter-style keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches. Following the decline of punch cards and paper tape, interaction via teleprinter-style keyboards became the main input device for computers.

A keyboard typically has characters engraved or printed on the keys and each press of a key typically corresponds to a single written symbol. However, to produce some symbols requires pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters, numbers or signs (characters), other keys or simultaneous key presses can produce actions or computer commands.

In normal usage, the keyboard is used to type text and numbers into a word processor, text editor or other program. In a modern computer, the interpretation of key presses is generally left to the software. A computer keyboard distinguishes each physical key from every other and reports all key presses to the controlling software. Keyboards are also used for computer gaming, either with regular keyboards or by using keyboards with special gaming features, which can expedite frequently used keystroke combinations. A keyboard is also used to give commands to the operating system of a computer, such as Windows' Control-Alt-Delete combination, which brings up a task window or shuts down the machine. Keyboards are the only way to enter commands on a command-line interface.

Touch screen

A touchscreen is an electronic visual display that can detect the presence and location of a touch within the display area. The term generally refers to touching the display of the device with a finger or hand. Touchscreens can also sense other passive objects, such as a stylus. Touchscreens are common in devices such as all-in-one computers, tablet computers, and smartphones.

The touchscreen has two main attributes. First, it enables one to interact directly with what is displayed, rather than indirectly with a pointer controlled by a mouse or touchpad. Secondly, it lets one do so without requiring any intermediate device that would need to be held in the hand. Such displays can be attached to computers, or to networks as terminals. They also play a prominent role in the design of digital appliances such as the personal digital assistant (PDA), satellite navigation devices, mobile phones, and video games.

Pen Computing

Pen computing refers to a computer user-interface using a pen (or stylus) and tablet, rather than devices such as a keyboard, joysticks or a mouse.

Pen computing is also used to refer to the usage of mobile devices such as wireless tablet PCs, PDAs and GPS receivers. The term has been used to refer to the usage of any product allowing for mobile communication. An indication of such a device is a stylus, generally used to press upon a graphics tablet or touchscreen, as opposed to using a more traditional interface such as a keyboard, keypad, mouse or touchpad.

Historically, pen computing (defined as a computer system employing a user-interface using a pointing device plus handwriting recognition as the primary means for interactive user input) predates the use of a mouse and graphical display by at least two decades, starting with the Stylator [1] and RAND tablet[2] systems of the 1950s and early 1960s

OPtical character Recognition

Optical character recognition, usually abbreviated to OCR, is the mechanical or electronic translation of scanned images of handwritten, typewritten or printed text into machine-encoded text. It is widely used to convert books and documents into electronic files, to computerize a record-keeping system in an office, or to publish the text on a website. OCR makes it possible to edit the text, search for a word or phrase, store it more compactly, display or print a copy free of scanning artifacts, and apply techniques such as machine translation, text-to-speech and text mining to it. OCR is a field of research in pattern recognition, artificial intelligence and computer vision.

OCR systems require calibration to read a specific font; early versions needed to be programmed with images of each character, and worked on one font at a time. "Intelligent" systems with a high degree of recognition accuracy for most fonts are now common. Some systems are capable of reproducing formatted output that closely approximates the original scanned page including images, columns and other non-textual components.

Speech recognition (also known as automatic speech recognition or computer speech recognition) converts spoken words to text. The term "voice recognition" is sometimes used to refer to recognition systems that must be trained to a particular speaker—as is the case for most desktop recognition software. Recognizing the speaker can simplify the task of translating speech.

Speech recognition

Speech recognition is a broader solution that refers to technology that can recognize speech without being targeted at single speaker—such as a call system that can recognize arbitrary voices.

Speech recognition applications include voice user interfaces such as voice dialing (e.g., "Call home"), call routing (e.g., "I would like to make a collect call"), domotic appliance control, search (e.g., find a podcast where particular words were spoken), simple data entry (e.g., entering a credit card number), preparation of structured documents (e.g., a radiology report), speech-to-text processing (e.g., word processors or emails), and aircraft (usually termed Direct Voice Input).

Source:Britannica Encyclopedia

Memory Devices

CPU

in full central processing unit

Principal component of a digital computer, composed of a control unit, an instruction-decoding unit, and an arithmetic-logic unit.

The CPU is linked to main memory, peripheral equipment (including input/output devices), and storage units. The control unit integrates computer operations. It selects instructions from the main memory in proper sequence and sends them to the instruction-decoding unit, which interprets them so as to activate functions of the system at appropriate moments. Input data are transferred via the main memory to the arithmetic-logic unit for processing (i.e., addition, subtraction, multiplication, division, and certain logic operations). Larger computers may have two or more CPUs, in which case they are simply called “processors” because each is no longer a “central” unit. See also multiprocessing.

Memory

In digital computers, a physical device used to store such information as data or programs on a temporary or permanent basis.

Most digital computer systems have two types of memory, the main memory and one or more auxiliary storage units. In most cases, the main memory is a high-speed RAM. Auxiliary storage units include hard disks, floppy disks, and magnetic tape drives. Besides main and auxiliary memories, other forms of memory include ROM and optical storage media such as videodiscs and compact discs (see CD-ROM).

RAM

in full Random-Access Memory

Computer main memory in which specific contents can be accessed (read or written) directly by the CPU in a very short time regardless of the sequence (and hence location) in which they were recorded.

Two types of memory are possible with random-access circuits, static RAM (SRAM) and dynamic RAM (DRAM). A single memory chip is made up of several million memory cells. In a SRAM chip, each memory cell stores a binary digit (1 or 0) for as long as power is supplied. In a DRAM chip, the charge on individual memory cells must be refreshed periodically in order to retain data. Because it has fewer components, DRAM requires less chip area than SRAM; hence a DRAM chip can hold more memory, though its access time is slower.

ROM

in full Read-Only Memory

Form of computer memory that does not lose its contents when the power supply is cut off and that is not rewritable once it is manufactured or written.

It is generally employed for programs designed for repeated use without modification, such as the start-up procedures of a personal computer; the ROM is used for storing the program used in the control unit of the computer. See also CD-ROM, compact disc.

CD-ROM

in full Compact Disc Read-Only Memory

Type of computer storage medium that is read optically (e.g., by a laser).

A CD-ROM drive uses a low-power laser beam to read digitized (binary) data that have been encoded onto an optical disc in the form of tiny pits, then feeds the data to a computer for processing. Because it uses digital data, a CD-ROM can store images and sound in addition to text and is thus used in video and audio devices to store music, graphics, and movies (see compact disc). Unlike conventional magnetic-storage technologies (e.g., hard disks), CD-ROM drives cannot write information (that is, accept the input of new data), hence the tag “read-only.” Recordable compact discs (called CD-R) must be written on a CD-R recorder and can be played on any CD-ROM drive.

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Hard Disk

Magnetic storage medium for a microcomputer.

Hard disks are flat, circular plates made of aluminum or glass and coated with a magnetic material. Hard disks for personal computers can store up to several gigabytes (billions of bytes) of information. Data are stored on their surfaces in concentric tracks. A small electromagnet, called a magnetic head, writes a binary digit (1 or 0) by magnetizing tiny spots on the spinning disk in different directions and reads digits by detecting the magnetization direction of the spots. A computer's hard drive is a device consisting of several hard disks, read/write heads, a drive motor to spin the disks, and a small amount of circuitry, all sealed in a metal case to protect the disks from dust. In addition to referring to the disks themselves, the term hard disk is also used to refer to the whole hard drive.

Floppy Disk

or diskette

Magnetic storage medium used with computers.

Floppy disks are made of flexible plastic coated with a magnetic material, and are enclosed in a hard plastic case. They are typically 3.5 in. (9 cm) in diameter. Data are arranged on their surfaces in concentric tracks. A disk is inserted in the computer's floppy disk drive, an assembly of magnetic heads and a mechanical device for rotating the disk for reading or writing purposes. A small electromagnet, called a magnetic head, writes a binary digit (1 or 0) onto the disk by magnetizing a tiny spot on the disk in different directions, and reads digits by detecting the magnetization direction of the spots. With the increasing use of e-mail attachments and other means to transfer files from computer to computer, the use of floppy disks has waned, though they are still widely used to keep second (backup) copies of valuable files.

computer -charles babage

Charles Babage

 born Dec. 26, 1791, London, Eng.

 died Oct. 18, 1871, London

British mathematician and  computer inventor.

Photograph:Charles Babbage, detail of an oil painting by Samuel Lawrence, 1845; in the National Portrait …  

Educated at Cambridge University, he devoted himself from about 1812 to devising machines capable of calculating mathematical tables. His first small calculator could perform certain computations to eight decimals. In 1823 he obtained government support for the design of a projected machine with a 20-decimal capacity. In the 1830s he developed plans for the so-called Analytical Engine, capable of performing any arithmetical operation on the basis of instructions from punched cards, a memory unit in which to store numbers, sequential control, and most of the other basic elements of the present-day computer. The forerunner of the modern digital computer, the Analytical Engine was never completed. In 1991 British scientists built Difference Engine No. 2 (accurate to 31 digits) to Babbage's specifications. His other contributions included establishing the modern postal system in England, compiling the first reliable actuarial tables, and inventing the locomotive cowcatcher.

Computer

Programmable machine that can store, retrieve, and process data.

Today's computers have at least one CPU that performs most calculations and includes a main memory, a control unit, and an arithmetic logic unit. Increasingly, personal computers contain specialized graphic processors, with dedicated memory, for handling the computations needed to display complex graphics, such as for three-dimensional simulations and games. Auxiliary data storage is usually provided by an internal hard disk and may be supplemented by other media such as floppy disks or CD-ROMs. Peripheral equipment includes input devices (e.g., keyboard, mouse) and output devices (e.g., monitor, printer), as well as the circuitry and cabling that connect all the components. Generations of computers are characterized by their technology. First-generation digital computers, developed mostly in the U.S. after World War II, used vacuum tubes and were enormous. The second generation, introduced c. 1960, used transistors and were the first successful commercial computers. Third-generation computers (late 1960s and 1970s) were characterized by miniaturization of components and use of integrated circuits. The microprocessor chip, introduced in 1974, defines fourth-generation computers.

Personal computer

Microcomputer designed for use by one person at a time.

A typical PC assemblage comprises a CPU; internal memory consisting of RAM and ROM; data storage devices (including a hard disc, a floppy disc, or CD-ROM); and input/output devices (including a display screen, keyboard, mouse, and printer). The PC industry began in 1977 when Apple Computer, Inc. (now Apple Inc.), introduced the Apple II. Radio Shack and Commodore Business Machines also introduced PCs that year. IBM entered the PC market in 1981. The IBM PC, with increased memory capacity and backed by IBM's large sales organization, quickly became the industry standard. Apple's Macintosh (1984) was particularly useful for desktop publishing. Microsoft Corp. introduced MS Windows (1985), a graphical user interface that gave PCs many of the capabilities of the Macintosh, initially as an overlay of MS-DOS. Windows went on to replace MS-DOS as the dominant operating system for personal computers. Uses of PCs multiplied as the machines became more powerful and application software proliferated. Today, PCs are used for word processing, Internet access, and many other daily tasks.

Analog computer

Computer in which continuously variable physical quantities, such as electrical potential, fluid pressure, or mechanical motion, are used to represent (analogously) the quantities in the problem to be solved.

The analog system is set up according to initial conditions and then allowed to change freely. Answers to the problem are obtained by measuring the variables in the analog model. Analog computers are especially well suited to simulating dynamic systems; such simulations may be conducted in real time or at greatly accelerated rates, allowing experimentation by performing many runs with different variables. They have been widely used in simulating the operation of aircraft, nuclear power plants, and industrial chemical processes. See also digital computer.

Digital computer

Computer capable of solving problems by processing information expressed in discrete form.

By manipulating combinations of binary digits (see binary code), it can perform mathematical calculations, organize and analyze data, control industrial and other processes, and simulate dynamic systems such as global weather patterns. See also analog computer.

Micro computer

Small digital computers whose CPU is contained on a single integrated semiconductor chip.

As large-scale and then very large-scale integration (VLSI) have progressively increased the number of transistors that can be placed on one chip, the processing capacity of microcomputers has grown immensely. The personal computer is the most common example of a microcomputer, but high-performance microcomputer systems are widely used in business, in engineering, and in “smart” machines in manufacturing. See also integrated circuit, microprocessor.

source:Britannica Encyclopedia