Computer hardware equals the collection of physical elements that comprise a computer system. Computer hardware refers to the physical parts or components of a computer such as monitor, keyboard, hard drive disk, mouse, printers, graphic cards, sound cards, memory, motherboard and chips, etc all of which are physical objects that you can actually touch. In contrast, software is untouchable. Software exists as ideas,application, concepts, and symbols, but it has no substance. A combination of hardware and software forms a usable computing system.
A flat board with grids of buttons which are programmed to input charactersinto the computer. Keyboards can be classified into different categoriesbased on their layout, connection type, form factor etc. The most commonkeyboard layout is QWERTY which has been adopted from the typewriter. Astandard keyboard includes about 100 keys, each of which sends a differentsignal to the CPU. It is connected to the computer through a PS/2 or an USBport. Wireless keyboards use wireless technologies to communicate. Mostcommonly used technologies are: Infrared, Radio frequencies and Bluetooth
VA pointing device that detects two dimensional motions on a surface and sends thesignal to the CPU. A mouse has two or more buttons and scroll wheels to allow usersto interact with the GUI. The traditional PC mouse has two buttons, while the traditionalMacintosh mouse has one button. Mouse with more than two buttons can beprogrammed for specific tasks like short cut, launch application etc. The scroll wheel isused for vertical and horizontal scrolling. A mouse helps the user to have the ability toperform various functions such as opening a program or file and does not require theuser to memorize commands.Mice can be classified into two different types: Ball and Optical. Ball mice areolder technology and almost obsolete. This type of mouse has ball and wheelmechanism which detects the motion and sends signal to the CPU. The opticalmouse does not use any wheel mechanism for motion detection. Instead it uses alight and a small optical sensor to detect the motion of the mouse by tracking atiny image of the desk surface. Optical mice avoid the problem of a dirty mouseball, which causes regular mice to roll unsmooth if the mouse ball and internalrollers are not cleaned frequently.
Trackballs are similar to mice except that the ball is bigger, remainsstationary on the desk unlike mouse and it is located on the top. Theuser uses fingers to roll the trackball and internal rollers sense themotion which is transmitted to the computer. Trackballs have theadvantage over mice in that the body of the trackball remainsstationary on the desk and doesn’t need as much room as the mice.Early laptop computers often used trackballs. Track balls are usedfor special purposes such as air traffic control room, radar consoleetc.
Touch screens are touch sensitive displays which can detect location of touches withinthe touch sensitive display. There are three basic systems that are used to recognize apersons touch:1)Resistive2)Capacitive3)Surface acoustic wave
The resistive system consists of a normal glass panel that is covered with a conductiveand a resistive metallic layer. These two layers are separated by thin space, and at thetop a scratch-resistant layer is placed. An electrical current runs through the two layerswhile the monitor is operational. When a user touches the screen, it causes a change inthe electrical current which is identified as a touch event and sent to the controllerpresent inside the circuit board for processing. Once the coordinates are known, aspecial driver translates the touch into something that the operating system canunderstand, similar to the computer mouse “click”.In the capacitive system, a layer that stores electrical charge is placed on the glasspanel of the monitor. The human body also carries electric charge. When a user touchesthe monitor with his or her finger, some of the charge is transferred to the user, so thecharge on the capacitive layer decreases. This fluctuation of current is measured by thecircuit which is present at each corner of the display. The computer calculates, from therelative differences in charge at each corner, exactly where the touch event took placeand then relays that information to the touch-screen driver software.On the monitor of a surface acoustic wave system, two transducers (one receivingand one sending) are placed along the X and Y axes of the monitors glass plate.Ultrasonic waves pass over the screen. . When the screen is touched, a portion of thewave is absorbed by the object or user. This change in the ultrasonic waves register’sthe position of the touch event and sends this information to the controller forprocessing
This is a devices that scans the printed materials and convert it into a digital form. Thescanner uses light to detect printed objects on paper. In case of a typical flatbedscanner, the document is placed face-down on a glass bed. A moving optical mechanismconsisting of a lamp, a mirror and a lens moves back and forth underneath the glass.The image sensor may be a CCD (Charged coupled device) or a CIS (Compact ImageSensor), a single row of sensor elements mounted very close to the document. Lightfrom the lamp bounces off the document and then through a set of optical mechanisms itis focused into the CCD. In the case of the CIS, the light and dark areas are picked updirectly by the sensor. The CCD/CIS digitizes the results via an analog-to-digitalconverter, and sends the resulting information to the scanners own hardware and thento the host PC.
Computer software, or just software, is acollection of computer programs and relateddata that provides the instructions for tellinga computer what to do and how to do it.Software refers to one or more computerprograms and data held in the storage of thecomputer. In other words, software is a set ofprograms, procedures, algorithms and itsdocumentation concerned with the operationof a data processing system. Programsoftware performs the function of theprogram it implements, either by directlyproviding instructions to the digitalelectronics or by serving as input to anotherpiece of software. The term was coined tocontrast to the old term hardware (meaningphysical devices). In contrast tohardware, software "cannot be touched"
System software is computer software or an operating system designed tooperate and control the computer hardware and to provide a platform forrunning application software.[Application software is computer software designed to help the user to performspecific tasks. Examples include enterprise software, accounting software,office suites, graphics software and media players
A component or peripheral device (such as a barcode reader, graphic tablet, keyboard.Input devices convert the users actions and analog data (sound, graphics, pictures)into digital electronic signals that can be processed by a computer.An output device is any piece of computer hardware equipment used to communicatethe results of data processing carried out by an information processing system (such as acomputer) which converts the electronically generated information into human-readableform..The system unit, also known as a "tower" or "chassis," is the main part of a desktopcomputer. It includes the motherboard, CPU, RAM, and other components. The systemunit also includes the case that houses the internal components of the computer.The term "system unit" is often used to differentiate between the computer andperipheral devices, such as the monitor, keyboard, and mouse.
In computer architecture, a bus is a subsystem that transfers databetween components inside a computer, or between computers.Early computer buses were parallel electrical wires with multipleconnections, but the term is now used for any physicalarrangement that provides the same logical functionality as aparallel electrical bus. Modern computer buses can use bothparallel and bit serial connections, and can be wired in either amultidrop (electrical parallel) or daisy chain topology, or connectedby switched hubs, as in the case of USB.
These buses carry data from one unit to other, it is a bi-directionalbus i.e the data can be carried in both directions.These buses carry address given by the CPU from one unit toanother in the computer.These buses carry control signal from ALU to memory and frommemory to alu and then to the output unit.
The main memory of the computer is also known asRAM, standing for Random Access Memory. It isconstructed from integrated circuits and needs tohave electrical power in order to maintain itsinformation. When power is lost, the information islost too! It can be directly accessed by the CPU.The access time to read or write any particular byteare independent of whereabouts in the memory thatbyte is, and currently is approximately 50nanoseconds (a thousand millionth of a second).This is broadly comparable with the speed at whichthe CPU will need to access data. Main memory isexpensive compared to external memory so it haslimited capacity. The capacity available for a givenprice is increasing all the time. For example manyhome Personal Computers now have a capacity of16 megabytes (million bytes), while 64 megabytesis commonplace on commercial workstations. TheCPU will normally transfer data to and from the mainmemory in groups of two, four or eight bytes, even ifthe operation it is undertaking only requires a singlebyte.
Secondary memory is a type of computermemory that is not directly accessed by thecentral processing unit (CPU) of a computerand is usually available as non-volatilememory. One of the most common forms ofthis memory is the hard drive of acomputer, which is used to store the operatingsystem (OS) and other programs. Other formsof secondary memory include disc drives forcompact discs (CDs) or digital versatile discs(DVDs), as well as removable flash memory.In contrast to this, primary memory iscomputer memory directly accessed by theCPU, usually volatile memory, and tertiarymemory refers to systems outside of acomputer that can be directly accessedthrough various means
The primary computer storage device. Like tape, it is magnetically recorded and can bere-recorded over and over. Disks are rotating platters with a mechanical arm that movesa read/write head between the outer and inner edges of the platters surface. It can takeas long as one second to find a location on a floppy disk to as little as a couple ofmilliseconds on a fast hard disk. See hard disk for more details.Tracks and SpotsThe disk surface is divided into concentric tracks (circles within circles). The thinner thetracks, the more storage. The data bits are recorded as tiny magnetic spots on thetracks. The smaller the spot, the more bits per inch and the greater the storage.SectorsTracks are further divided into sectors, which hold a block of data that is read or writtenat one time; for example, READ SECTOR 782, WRITE SECTOR 5448. In order toupdate the disk, one or more sectors are read into the computer, changed and writtenback to disk. The operating system figures out how to fit data into these fixed spaces.Modern disks have more sectors in the outer tracks than the inner ones because theouter radius of the platter is greater than the inner radius (see CAV). See magnetic tapeand optical disc.
Random-access memory (RAM) is a form of computer data storage. A random-accessdevice allows stored data to be accessed in very nearly the same amount of time for anystorage location, so data can be accessed quickly in any random order. Incontrast, other data storage media such as hard disks, CDs, DVDs and magnetictape, as well as early primary memory types such as drum memory, read and write dataonly in a predetermined order, consecutively, because of mechanical design limitations.Therefore the time to access a given data location varies significantly depending on itsphysical location.Today, random-access memory takes the form of integrated circuits. Strictlyspeaking, modern types of DRAM are not random access, as data is read inbursts, although the name DRAM / RAM has stuck. However, many types ofSRAM, ROM, OTP, and NOR flash are still random access even in a strict sense. RAMis often associated with volatile types of memory (such as DRAM memorymodules), where its stored information is lost if the power is removed. Many other typesof non-volatile memory are RAM as well, including most types of ROM and a type offlash memory called NOR-Flash. The first RAM modules to come into the market werecreated in 1951 and were sold until the late 1960s and early 1970s.