Text 1. PROGRAMMING LANGUAGES

a) __________ Some, but not all, authors restrict the term "programming language" to those languages that can express all possible algorithms.

b) __________ However, the usage of both terms varies among authors, including the exact scope of each. One usage describes programming languages as a subset of computer languages. In this vein, languages used in computing that have a different goal than expressing computer programs are generically designated computer languages. For instance, markup languages are sometimes referred to as computer languages to emphasize that they are not meant to be used for programming. Another usage regards programming languages as theoretical constructs for programming abstract machines, and computer languages as the subset there of that runs on physical computers, which have finite hardware resources. It is emphasized that formal specification languages are just as much programming languages as are the languages intended for execution.

c) __________ Each language has a unique set of keywords (words that it understands) and a special syntax for organizing program instructions. High-level programming languages, while simple compared to human languages, are more complex than the languages the computer actually understands, called machine languages. Machine languages are the only languages understood by computers. While easily understood by computers, machine languages are almost impossible for humans to use because they consist entirely of numbers. Programmers, therefore, use either a high-level programming language or an assembly language. An assembly language contains the same instructions as a machine language, but the instructions and variables have names instead of being just numbers. Programs written in high-level languages are translated into assembly language or machine language by a compiler. Assembly language programs are translated into machine language by a program called an assembler. Each type of CPU has its own machine language and assembly language, so an assembly language program written for one type of CPU won't run on another.

d) __________ Now, most programs are written in a high-level language such as FORTRAN or C. Programmers still use assembly language when speed is essential or when they need to perform an operation that isn't possible in a high-level language. A programming language such as C, FORTRAN, or Pascal that enables a programmer to write programs that are more or less independent of a particular type of computer. Such languages are considered high-level because they are closer to human languages and further from machine languages. In contrast, assembly languages are considered low-level because they are very close to machine languages. The main advantage of high-level languages over low-level languages is that they are easier to read, write, and maintain. Ultimately, programs written in a high-level language must be translated into machine language by a compiler or interpreter. The first high-level programming languages were designed in the 1950s. Now there are dozens of different languages, including Algol, BASIC, COBOL, C, C++, FORTRAN, Pascal, and Prolog.

e) __________ 4GLs are far removed from machine languages and represent the class of computer languages closest to human languages. Often abbreviated 4GL, fourth-generation languages are programming languages closer to human languages than typical high-level programming languages. Most 4GLs are used to access databases. For example, a typical 4GL command is FIND ALL RECORDS WHERE NAME IS "SMITH" The other four generations of computer languages are: first generation: machine language; second generation: assembly language; third generation: high-level programming languages, such as C,C++; fourth generation: languages used for artificial intelligence and neural networks. Regardless of what language you use, you eventually need to convert your program into machine language so that the computer can understand it. There are two ways to do this: 1) compile the program; 2) interpret the program. The question of which language is best is one that consumes a lot of time and energy among computer professionals. Every language has its strengths and weaknesses. For example, FORTRAN is a particularly good language for processing numerical data, but it does not lend itself very well to organizing large programs. Pascal is very good for writing well-structured and readable programs, but it is not as flexible as the C programming language. C++ embodies powerful object-oriented features, but it is complex and difficult to learn. The choice of which language to use depends on the type of computer the program is to run on, what sort of program it is, and the expertise of the programmer.

3. Answer the questions on the text:

1) How do authors restrict the term "programming language"? 2) What organizes program instructions? 3) What types of languages can computers understand? 4) What do you have to do to make the computer understand your program? 5) Why are assembly languages considered to be low-level? 6) What does the choice of the language to use depend on?

4. Look at the text again and complete the sentences:

1) A programming language is …

2) Programming languages can be described as … and …

3) The term “programming language” usually refers to …

4) The four generations of computer languages are …

5) The main advantage of high-level languages over low-level languages is …

6) You convert a program to make the computer understand it in two ways. They are …

5. Retell the text using the following phrases:

The text I’m going to retell is devoted to …

First of all, the author draws our attention to the fact that …

In the next passage the author’s attention is focused on …

The examples mentioned in this text illustrate well enough …

According to the text …

The author arrives to the following conclusions: …

I find the text rather difficult/interesting/challenging, because …

<== попередня сторінка	\|	наступна сторінка ==>
READING	\|	Read Text 2 about the popular programming languages and say what fields of programming these languages are used in?

Не знайшли потрібну інформацію? Скористайтесь пошуком google:

Генерація сторінки за: 0.003 сек.