Java pro grammers do nt write co de with specif ic o

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Unformatted text preview: den Technology’s first customers? Who were among their first investors? 6. What are the security risks associated with connectivity, the I nternet, and distributed processing? 9.5 Writing Software L E A RN I N G OBJ E C T I V E S 1. Understand, at a managerial level, what programming languages are and how software is developed. 2. Recogniz e that an operating system and microprocessor constrain the platform upon which most compiled application software will run. 3. Understand what Java is and why it is significant. 4. Know what scripting languages are. So yo u’ve go t a great idea that yo u want to express in so f tware—ho w do yo u go abo ut creating a pro gram? P ro grammers write so f tware in a programming language. While each language has its strengths and weaknesses, mo st co mmercial so f tware is written in a variant o f the C pro gramming language such as C++ (pro no unced “see plus plus”), C# (pro no unced “see sharp”), o r Objective C (po pular f o r iOS app develo pment). Visual Basic (f ro m Micro so f t) and Java (f ro m Sun) are also amo ng the mo re po pular o f the do zens o f pro gramming languages available. Web develo pers may f avo r specialty languages like Ruby and P ytho n, while languages like SQL are used in databases. Mo st pro f essio nal pro grammers use an int egrat ed development environment (IDE) to write their co de. The IDE includes a text edito r, a debugger f o r sleuthing o ut erro rs, and o ther usef ul pro gramming to o ls. The mo st po pular IDE f o r Windo ws is Visual Studio , while Apple o f f ers the Xco de IDE. Mo st IDEs can suppo rt several dif f erent pro gramming languages. The IDE will also compile a pro grammer’s co de, turning the higher-level lines o f instructio ns that are readable by humans into lo wer-level instructio ns expressed as the patterns o f o nes and zero s that are readable by a co mputer’s micro pro cesso r. Figure 9. 8 Micros oft ’ s Vis ual St udio IDE s up p ort s des kt op , s erver, mobile, and cloud comp ut ing s oft ware develop ment . Lo o k at the side o f a bo x o f co mmercial so f tware and yo u’re likely to see system requirements that specif y the o perating system and pro cesso r that the so f tware is designed f o r (e.g., “this so f tware wo rks o n co mputers with Windo ws 7 and Intel-co mpatible pro cesso rs”). Wo uldn’t it be great if so f tware co uld be written o nce and run everywhere? That’s the idea behind Java—a pro gramming language develo ped by Sun Micro systems. Java pro grammers do n’t write co de with specif ic o perating system co mmands (say f o r Windo ws, Mac OS X, o r Linux), instead they use special Java co mmands to co ntro l their user interf ace o r interact with the display and o ther hardware. Java pro grams can run o n any co mputer that has a Java Virtual Machine (JVM), a so f tware layer that interprets Java co de so that it can be understo o d by the o perating system and pro cesso r o f a given co mputer. Java’s platf o rm independence—the ability f o r develo pers to “write o nce, run everywhere”—is its biggest selling po int. Many Web sites execute Java applets to run the animatio n yo u might see in advertisements o r games. Java has also been deplo yed o n o ver six billio n mo bile pho nes wo rldwide, and is po pular amo ng enterprise pro grammers who want to be sure their pro grams can scale f ro m smaller hardware up to high-end superco mputers. As lo ng as the machine receiving the Java co de has a JVM, then the Java applicatio n sho uld run. Ho wever, Java has no t been po pular f o r deskto p applicatio ns. Since Java isn’t o ptimized to take advantage o f interf ace elements specif ic to the Mac o r Windo ws, mo st Java deskto p applicatio ns lo o k clunky and unnatural. Java co de that runs thro ugh the JVM interpreter is also slo wer than co de co mpiled f o r the native OS and pro cesso r that make up a platf o rm.So me o f f erings have attempted to o verco me the speed issues asso ciated with interpreting Java co de. Just-in-time co mpilatio n sto res co de in native pro cesso r-executable f o rm af ter each segment is initially interpreted, f urther helping to speed executio n. Other enviro nments allo w f o r Java to be co mpiled ahead o f time so that it can be directly executed by a micro pro cesso r. Ho wever, this pro cess eliminates co de po rtability—Java’s key selling po int. And develo pers preparing their co de f o r the JVM actually preco mpile co de into so mething called Java byteco de, a f o rmat that’s less human f riendly but mo re quickly interpreted by JVM so f tware. Scripting languages are the f inal catego ry o f pro gramming to o l that we’ll co ver. Script ing languages typically execute within an applicatio n. Micro so f t o f f ers a scripting language called VB Script (a derivative o f Visual Basic) to auto mate f unctio ns in Of f ice. And mo st bro wsers and Web servers suppo rt JavaScript, a language that helps make the Web mo re i...
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This document was uploaded on 01/31/2014.

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