IntroductionComputer Hardware is the physical part of a computer, asdistinguished from the computer software that executes or runs onthe hardware. The hardware of a computer is infrequentlychanged, while software and data are modified frequently. The termsoft refers to readily created, modified, or erased. These are unlikethe physical components within the computer which are hard.When you think of the term computer hardware you probably thinkof the guts inside your personal computer at home or the one in yourclassroom. However, computer hardware does not specifically referto personal computers. Instead, it is all types of computer systems.Computer hardware is in embedded systems inautomobiles, microwave ovens, CD players, DVD players, and manymore devices. In 2003, only 0.2% of all microprocessors sold were forpersonal computers. How many other things in your house or yourclassroom use computer hardware?
MOTHERBOARDThe motherboard is the body or mainframe of thecomputer, through which all other components interface. It isthe central circuit board making up a complex electronicsystem. A motherboard provides the electrical connections bywhich the other components of the system communicate. Themother board includes many components such as: centralprocessing unit (CPU), random access memory(RAM), firmware, and internal and external buses.
CENTRAL PROCESSING UNITThe Central Processing Unit (CPU; sometimes just calledprocessor) is a machine that can execute computer programs. Itis sometimes referred to as the brain of the computer.There are four steps that nearly all CPUs use in theiroperation: fetch, decode, execute, and write back. The firststep, fetch, involves retrieving an instruction from programmemory. In the decode step, the instruction is broken up intoparts that have significance to other portions of the CPU. Duringthe execute step various portions of the CPU, such as thearithmetic logic unit (ALU) and the floating point unit (FPU) areconnected so they can perform the desired operation. The finalstep, write back, simply writes back the results of the executestep to some form of memory.
RANDOM ACCESS MEMORYRandom access memory (RAM) is fast-access memory that iscleared when the computer is power-down. RAM attachesdirectly to the motherboard, and is used to store programsthat are currently running. RAM is a set of integrated circuitsthat allow the stored data to be accessed in any order (why itis called random). There are many different types of RAM.Distinctions between these different types include: writable vs.read-only, static vs. dynamic, volatile vs. non-volatile, etc.
FIRMWAREFirmware is loaded from the Read only memory (ROM) run fromthe Basic Input-Output System (BIOS). It is a computer programthat is embedded in a hardware device, for example amicrocontroller. As it name suggests, firmware is somewherebetween hardware and software. Like software, it is a computerprogram which is executed by a microprocessor or amicrocontroller. But it is also tightly linked to a piece ofhardware, and has little meaning outside of it. Most devicesattached to modern systems are special-purpose computers intheir own right, running their own software. Some of thesedevices store that software (“firmware”) in a ROM within thedevice itself.
REMOVABLE MEDIA DEVICESIf your putting something in your computer and taking it out ismost likely a form of removable media. There are many differentremovable media devices. The most popular are probably CD andDVD drives which almost every computer these days has at leastone of. There are some new disc drives such as Blu-ray which canhold a much larger amount of information then normal CDs orDVDs. One type of removable media which is becoming lesspopular is floppy disk.
CDCDs are the most common type of removable media. They areinexpensive but also have short life-span. There are a fewdifferent kinds of CDs. CD-ROM which stands for Compact Discread-only memory are popularly used to distribute computersoftware although any type of data can be stored on them. CD-Ris another variation which can only be written to once but canbe read many times. CD-RW (rewritable) can be written to morethan once as well as read more than once. Some other types ofCDs which are not as popular include Super Audio CD(SACD), Video Compact Discs (VCD), Super Video Compact Discs(SVCD), PhotoCD, Pictured, CD-i, and Enhanced CD.
There are two types of devices in a computer that use CDs: CD-ROM drive and a CD writer. The CD-ROM drive used for readinga CD. The CD writer drive can read and write a CD. CD writersare much more popular are new computers than a CD-ROMdrive. Both kinds of CD drives are called optical disc drivesbecause the use a laser light or electromagnetic waves to reador write data to or from a CD.
DVDDVDs (digital versatile discs) are another popular optical discstorage media format. The main uses for DVDs are video anddata storage. Most DVDs are of the same dimensions as compactdiscs. Just like CDs there are many different variations. DVD-ROMhas data which can only be read and not written. DVD-R andDVD+R can be written once and then function as a DVD-ROM.DVD-RAM, DVD-RW, or DVD+RW hold data that can be erasedand re-written multiple times. DVD-Video and DVD-Audio discsrespectively refer to properly formatted and structured videoand audio content. The devices that use DVDs are very similar tothe devices that use CDs. There is a DVD-ROM drive as well as aDVD writer that work the same way as a CD-ROM drive and CDwriter. There is also a DVD-RAM drive that reads and writes tothe DVD-RAM variation of DVD.
BLU-RAYBlu-ray is a newer optical disc storage media format. Its mainuses are high-definition video and data storage. The disc has thesame dimensions as a CD or DVD. The term “Blu-ray” comesfrom the blue laser used to read and write to the disc. The Blu-ray discs can store much more data then CDs or DVDs. A duallayer Blu-ray disc can store up to 50GB, almost six times thecapacity of a dual layer DVD (WOW!). Blu-ray discs have similardevices used to read them and write to them as CDs have. A BD-ROM drive can only read a Blu-ray disc and a BD writer can readand write a Blu-ray disc.
FLOPPY DISCA floppy disk is a type of data storage that is composed of a diskof thin, flexible(“floppy”) magnetic storage medium encased in asquare or rectangular plastic shell. Floppy disks are read andwritten by a floppy disk drive. Floppy disks are a dying and beingreplaced by the optical and flash drives. Many new computersdo not come with floppy drives anymore but there are a lot ofolder ones with floppy drives lying around. While floppy disksare very cheap the amount of storage on them compared to theamount of storage for the price of flash drives makes floppydisks unreasonable to use.
INTERNAL STORAGEInternal storage is hardware that keeps data inside thecomputer for later use and remains persistent even whenthe computer has no power. There are a few different typesof internal storage. Hard disks are the most popular type ofinternal storage. Solid-state drives have grown in popularityslowly. A disk array controller is popular when you needmore storage then a single hard disk can hold.
HARD DISK DRIVEA hard disk drive (HDD) is a non-volatile storage devicewhich stores digitally encoded data on rapidly rotatingplatters with magnetic surfaces. Just about every newcomputer comes with a hard disk these days unless it comeswith a new solid-state drive. Typical desktop hard disk drivesstore between 120 and 400GB, rotate at 7,200 rpm, andhave a media transfer rate of 1 Gigabyte/second or higher.Hard disk drives are accessed over one of a number of bustypes, including parallel ATA(also called IDE), Serial ATA(SATA), SCSI, Serial Attached SCSI, and Fiber Channel.
SOLID–STATE DRIVEA solid-state drive (SSD) is a data storage device thatuses solid-state memory to store persistent data. AnSSD emulates a hard disk drive, thus easily replacing itin any application. SSDs have begun to appear inlaptops because they can be smaller than HDDs. SSDsare currently more expensive per unit of capacity thanHDDs which is why they have not caught on so quickly.
DISK ARRAY CONTROLERA disk array controller is a device which manage thephysical disk drives and presents them to thecomputer as logical units. It almost alwaysimplements hardware RAID. RAID (Redundant Arrayof Independent Drives) is a technology that employsthe simultaneous use of two or more hard diskdrives to achieve greater levels ofperformance, reliability, and/or larger data volumesizes. A disk array controller also provides additionaldisk cache.