понедельник, 4 марта 2019 г.
Computer programming Essay
1. What common programming language statement, in your opinion, is most deleterious to readability and why do you think that?The go to statement in my opinion hindquarters be the most detrimental to program readability, beca spend up it practises it ticklish to keep track of where the program has been and will go during debugging. Extensive substance ab expend of go to statements make it difficult to impossible to keep the program cipher in a top down format.2. How does the chance uponing amid upper- and lowercase in identifiers push the three criteria?The affect to readability can be demonstrable when it is utilized in conjunction with a cohesive programming technique. The persona of upper case letters to help certain causes of identifiers stand give away in the code can be highly beneficial.The affect on writability will be positivistic because the readability of a program helps to amend the writability.The affect on reliability will also be positive degree bec ause the more readable, and writable a language then there is a positive affect on the reliability.3. How do type declaration statements for innocent variables affect the readability of a language?Having type declarations that are easy to scan are very important to the readability of a programming language. When the type declarations are cryptic or easily confused it degrades the readability because it is non as easy to identify the variable type or distinguish between them.4. Write an evaluation of java and of C++, using the criteria set forth in this chapter. Please be radical and provide a terra firma/justification for your evaluation.C++ReadabilityC++ is not an overall simple language which complicates its readability. It does however take over very good control structures and entropy type structures which can help the readability. But in general it can be difficult to read.WritabilityC++ allows for high levels of selective information abstraction, and expressivitys in the language allowing the programmer to create a myriad of structures to solve distinct programming problems making it very writable.ReliabilityC++ has extensive exclusion treatment and type checking capabilities, which lead to a more reliable language.JavaReadabilityJava because it is a functional programming language, which is structured tout ensemble unlikely than all other common programming languages. All of the computations in Java are carried out by applying functions to arguments. Java does not have the assignment statements or variables common in other languages. Alone this causes passable of a problem with the readability of Java, but the syntax for Java is double ambiguous because the same exact syntax is used for both data and function calls.WritabilityJava has a high amount of expressivitys with the use of functions, but the difficulties that can be encountered in readability will affect the writability of the language.ReliabilityJava does not have the extensive exception handling of C++.5. Evaluate both Java and C++ with respect to the crowning(prenominal) total cost (as discussed in Chapter 1 of the Sebesta text). Again, please be thorough and provide a reason/justification for your evaluation.The total cost of C++ is acceptable. C++ is a very complex language that for a programmer to learn completely can take well over a year, but a programmer can learn enough to make powerful programs in a relatively bypass time. The style constructs of C++ help to improve its maintainability over time which is a major component to the cost of software development.The total cost of Java is potentially more than that of C++. The functional programming environment is sufficiently different from all other imperative languages that training for programmers to learn and become dependable in Java can take longer. Also the syntax similarities with data will make tutelage costs for Java programs to be high because of their poor readability.Readability. Re quiring the declaration of variables forces the programmer to document his/her expectations regarding variable names, data types, and place setting (the region of the program where the variable will be applicable). Thus, the program becomes overmuch more readable to the programmer and to others.Writability. Requiring the declaration of variables may actually falloff writability in its most direct sense, since a programmer cannot simply use variables as needed, but must write declarations in their catch places to nullify error messages. This cast upd burden on the programmer can increase programming time. On the other hand, without declarations there can be no topical anesthetic variables, and the use of local variables can increase writability by allowing the programmer to reuse names without worrying about non-local references. Forcing the programmer to plan the use of variables may also improve writability over the long run.Efficiency. As we saw, readability and writability can be viewed as efficiency issues from the point of view of maintenance and software engineering, so the comments about those issues also apply here in that sense. The use of declarations may also permit more high-octane executing of the program. Without declarations, if no assumptions are made about the size of variables, less efficient access mechanisms using pointers must be used. Also, the programmer can use declarations to specify the exact size of variable needed (such as short int or long int). Restricting scope by using local variables can also save memory space by allowing the automatic rifle deallocation of variables. Note, however, that Fortran is a very efficient language in terms of movement speed, so it is not always true that requiring declarations must improve effectuation speed.Also, speed of translation may actually be decreased by the use of declarations, since more information must be kept in tables to keep track of the declarations. (It is not true, as Fo rtran and BASIC attest, that without declarations a translating program must be multi-pass.) Security. Requiring declarations enhances the translators ability to track the use of variables and report errors. A clear example of this appears in the difference between ANSI C and old-style Unix C. Early C did not require that parameters to functions be declared with function prototypes. (While not exactly variable declarations, parameter declarations are well related and can be viewed as essentially the same concept.) This meant that a C compiler could not guarantee that a function was called with the appropriate number or types of parameters. Such errors only appeared as crashes or dribble values during program execution.The use of parameter declarations in ANSI C greatly improved the security of the C language. Expressiveness. Expressiveness may be reduced by requiring the declaration of variables, since they cannot then be used in arbitrary ways. Scheme, for example, piece of mus ic requiring declarations, does not require that data types be given, so that a iodin variable can be used to store data of each data type. This increases expressiveness at the cost of efficiency and security.