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Doc21 - 12 Chapter 1 company Ahslracllorrl and redrnolugy...

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Unformatted text preview: 12 Chapter 1 company Ahslracllorrl and redrnolugy highelevul programming language it portahle language such as c, c+—.. lava, orVirual Basic that is composed or words and nlgchlaic natatinn that can he translated by a compiler into assembly language. to write one line for every instruction that the computer will follow, forcing the programmer to think like the computer. ' The recognition that a program could be written to lranslat: a more powerful language into computer instructions was one of the great breakthroughs ill the early days of computing. Programmers today owe their pruduciivilyiund their sanity—to the creation orlu'gh-level programming languages and compilers that translate programs in such languages into instructions. Figure 1.3 shows the rzlar tionships among these programs and languages. High-level snaot-nt vi], lrlL kl language lllll. Kelllt): program tenp -= vlkl: ttnet viti : vilell; vl‘<+1] e temp; @ Assemuly strap: language atli 52, s5,4 program adrl 32, 5432 (luerPs) lw 315. mm lw $16. 4021 SN S16, ntszr 5w S13, 4M2) Jr S31 Btnarymaclilnu nuunououlCluonotnnouuuuuacollnua language UllUllDlllJLlDl’lOliDODDIlOHDOUDClUDUU', program lBUDl103111lODDlDDCDUUDOUDDQDDflDD (lorMIFS) 10001100111toulnncououoouonuolco lDlfl OD]lllDUlUflC‘OUUUODDOflCODC(l 101 t ODDIIUOULDUOUUDDDDUDUUWDD 000000111llUOflDDDOIllJ/JUDUUUUUUC‘O noun: 1.3 c rungrlm oompirotl lMtn anemlrly language and than au‘mhl-d irm: hlnury maenrne language. Although the translation tront htglrlevrl language to htaary machine language is shown in two steps. same trrmpilrrs out out are middleman and produra binary niuchirllt- language directly. These languages and this ptogtatn are examined in more detail in chapter a. La Under the Cwlrs 13 A roinpilet enables a programmer to write this highrlevel language expression: A+B The compiler would compile it into this assembly language statement: add A,B As shown above. the assembler would lrallslalc this statement into the biliary instructions that tell the computer to add the two numbers A and E. Higltelevel programming languages offer several important benefits. First, they allow the programmer to think in a more natural language, using English words and algebraic notation, resulting in programs that look much more like text than like tables or eryptie symbols (see Figure 1.3). Moreover. they allow languages to be designed according to their intended use. Hence. Furlran was designed for scientific computation. Cohol for business data prneessing, Lisp ror symbol manipulation, and so on. There are also darn 'nrspecific languages for even narrower groups of users, such as those interested in simulation of fluids, for example. The second advantage of programming languages is improved programmer productivity. Onc orthe few areas of widespread agreement in software develop mom is that it takes less time to develop programs when they are written in languages that require fcwcr lines to express an idea, Coneiseness is a clear advantage alliiglrrlevcl languages over assenthlylanguage. The final advantage is that programming languages allow programs to be inde- pendent of the computer on which they were developed, some compilers and assemblers cati translate highrlevel language programs to the biliary instructions ofany computer. These three advantages are so strong lhat today little prograntr ming is done in asscmbly‘ language. Under the Covers Now that we have looked below your program to uncover the underlying software, let's open the enters ofyuul' Computer to learn about the underlying hardware. The underlying hardware in any com pater performs the same basic functions: inputting data, outputting data, processing data, and storing data How these Functions are performed is the primary topic or this hook, and subsequent rhaptet-s deal with different parts of these four tasks. When we come to an important point in this book, a point so important that we hope you will remember it forever. we emphasut: it by identirying it as a Big Picture item. We ltaVc about a dozen Big Pictures in this boolt, the first being ...
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