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<h3>Computer Science</h3>
<pre><![if !supportEmptyParas]> <![endif]><o:p></o:p></pre><pre>Even before the first computer was conceptualized, data had already been</pre><pre>stored on hard copy medium and used with a machine.<span style="mso-spacerun: yes"> </span>As early as 1801, the</pre><pre>punched card was used as a control device for mechanical looms.<span style="mso-spacerun: yes"> </span>One and</pre><pre>one-half centuries later, IBM joined punched cards to computers, encoding</pre><pre>binary information as patterns of small rectangular holes.<span style="mso-spacerun: yes"> </span>Today, punch</pre><pre>cards are rarely used with computers. Instead, they are used for a handful</pre><pre>of train tickets and election ballots.<span style="mso-spacerun: yes"> </span>Although some may find it</pre><pre>surprising, a computer printout is another type of hard copy medium.<span style="mso-spacerun: yes"> </span></pre><pre>Pictures, barcodes, and term papers are modern examples of data storage</pre><pre>that can later be retrieved using optical technology.<span style="mso-spacerun: yes"> </span>Although it</pre><pre>consumes physical space and requires proper care, non-acidic paper</pre><pre>printouts can hold information for centuries.<span style="mso-spacerun: yes"> </span>If long-term storage is not</pre><pre>of prime concern, magnetic medium can retain tremendous amounts of data</pre><pre>and consume less space than a single piece of paper.</pre><pre><![if !supportEmptyParas]> <![endif]><o:p></o:p></pre><pre>The magnetic technology used for computer data storage is the same</pre><pre>technology used in the various forms of magnetic tape from audiocassette</pre><pre>to videocassette recorders.<span style="mso-spacerun: yes"> </span>One of the first computer storage devices was</pre><pre>the magnetic tape drive. Magnetic tape is a sequential data storage</pre><pre>medium. To read data, a tape drive must wind through the spool of tape to</pre><pre>the exact location of the desired information. To write, the tape drive</pre><pre>encodes data sequentially on the tape. Because tape drives cannot randomly</pre><pre>access or write data like disk drives, and are thus much slower, they have</pre><pre>been replaced as the primary storage device with the hard drive.<span style="mso-spacerun: yes"> </span>The hard</pre><pre>drive is composed of thin layers of rigid magnetic platters stacked on top</pre><pre>of one another like records in a jukebox, and the heads that read and</pre><pre>write data to the spinning platters resemble the arm of a record player.<span style="mso-spacerun: yes"> </span></pre><pre>Floppy disks are another common magnetic storage medium.<span style="mso-spacerun: yes"> </span>They offer</pre><pre>relatively small storage capacity when compared to hard drives, but unlike</pre><pre>hard drives, are portable.<span style="mso-spacerun: yes"> </span>Floppy disks are constructed of a flexible</pre><pre>disk covered by a thin layer of iron oxide that stores data in the form of</pre><pre>magnetic dots. A plastic casing protects the disk: soft for the 51/4-inch</pre><pre>disk, and hard for the 31/2-inch disk.<span style="mso-spacerun: yes"> </span>Magnetic storage medium, for all</pre><pre>its advantages, only has a life expectancy of twenty years.</pre><pre><![if !supportEmptyParas]> <![endif]><o:p></o:p></pre><pre>Data can be stored on electronic medium, such as memory chips.<span style="mso-spacerun: yes"> </span>Every</pre><pre>modern personal computer utilizes electronic circuits to hold data and</pre><pre>instructions.<span style="mso-spacerun: yes"> </span>These devices are categorized as RAM (random access memory)</pre><pre>or ROM (read-only memory), and are compact, reliable, and efficient.<span style="mso-spacerun: yes"> </span>RAM</pre><pre>is volatile, and is primarily used for the temporary storage of programs</pre><pre>that are running.<span style="mso-spacerun: yes"> </span>ROM is non-volatile, and usually holds the basic</pre><pre>instruction sets a computer needs to operate.<span style="mso-spacerun: yes"> </span>Electronic medium is</pre><pre>susceptible to static electricity damage and has a limited life</pre><pre>expectancy, but in the modern personal computer, electronic hardware</pre><pre>usually becomes obsolete before it fails.<span style="mso-spacerun: yes"> </span>Optical storage medium, on the</pre><pre>other hand, will last indefinitely.</pre><pre><![if !supportEmptyParas]> <![endif]><o:p></o:p></pre><pre>Optical storage is an increasingly popular method of storing data.<span style="mso-spacerun: yes"> </span></pre><pre>Optical disk drives use lasers to read and write to their medium. When</pre><pre>writing to an optical disk, a laser creates pits on its surface to</pre><pre>represent data. Areas not burned into pits by the laser are called lands.</pre><pre>The laser reads back the data on the optical disk by scanning for pits and</pre><pre>lands. There are three primary optical disk mediums available for storage:</pre><pre>CD-ROM (compact disc read-only memory), WORM (write once read many), and</pre><pre>rewritable optical disks. The CD-ROM is, by far, the most popular form of</pre><pre>optical disk storage; however, CD-ROMs are read-only. At the factory,</pre><pre>lasers are used to create a master CD-ROM, and a mold is made from the</pre><pre>master and used to create copies. WORM drives are used almost exclusively</pre><pre>for archival storage where it is important that the data cannot be changed</pre><pre>or erased after it is written, for example, financial record storage.</pre><pre>Rewritable optical disks are typically used for data backup and archiving</pre><pre>massive amounts of data, such as image databases.</pre><pre><![if !supportEmptyParas]> <![endif]><o:p></o:p></pre><pre>Although there are many manufacturers of the data storage devices used in</pre><pre>the modern personal computer, each fits into one of four technological</pre><pre>classes according to the material and methods it uses to record</pre><pre>information.<span style="mso-spacerun: yes"> </span>Hardcopy medium existed before the invention of the</pre><pre>computer, and magnetic medium is predominantly used today.<span style="mso-spacerun: yes"> </span>Electronic</pre><pre>medium is used by every computer system, and is used to store instructions</pre><pre>or temporarily hold data.<span style="mso-spacerun: yes"> </span>Finally, optical storage medium utilizes lasers</pre><pre>to read and write information to a disk that lasts indefinitely.<span style="mso-spacerun: yes"> </span>Each</pre><pre>type of medium is suitable for certain functions that computer users</pre><pre>require. Although they use differing technologies, they all have equal</pre><pre>importance in the modern personal computer system.</pre></div>
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