Text 5. Programming Languages

A programming language is an artificial language that can be used to control the behavior of a machine, particularly a computer. Programming languages, like human languages, are defined through the use of syntactic and semantic rules, to determine structure and meaning respectively.

Programming languages are used to facilitate communication about the task of organizing and manipulating information, and to express algorithms precisely. Thousands of different programming languages have been created, and new ones are created every year.

There is no precise definition, but traits often consider important requirements and objectives of the language to be characterized as a programming language. Let’s speak about their function, target, construct and expressive power.

Function: A programming language is a language used to write computer programs, which instruct a computer to perform some kind of computation, and/or organize the flow of control between external devices (such as a printer, a robot, or any peripheral).

Target: Programming languages differ from natural languages in that natural languages are only used for interaction between people, while programming languages also allow humans to communicate instructions to machines. In some cases, programming languages are used by one program or machine to program another; PostScript source code, for example, is frequently generated programmatically to control a computer printer or display.

Constructs: Programming languages may contain constructs for defining and manipulating data structures or for controlling the flow of execution.

Expressive power: The theory of computation classifies languages by the computations they can express. All Turing complete languages can implement the same set of algorithms. ANSI/ISO SQL and Charity are examples of languages that are not Turing complete yet often called programming languages.

Non-computational languages, such as markup languages like HTML or formal grammars like BNF, are usually not considered programming languages. It is a usual approach to embed a programming language into the non-computational (host) language, to express templates for the host language.

What is the purpose of programming languages? A prominent purpose of programming languages is to provide instructions to a computer. As such, programming languages differ from most other forms of human expression in that they require a greater degree of precision and completeness. When using a natural language to communicate with other people, human authors and speakers can be ambiguous and make small errors, and still expect their intent to be understood. However, computers do exactly what they are told to do, and cannot understand the code the programmer “intended” to write. The combination of the language definition, the program, and the program’s inputs must fully specify the external behavior that occurs when the program is executed.

All the programming languages can be divided into high-level languages and machine-level languages. High-level languages such as BASIC or FORTRAN are machine independent because any program written in this language can easily be executed by different computer system, they are easy to learn and produce fast results. On the other hand, machine-level languages such as assembly languages require that computer and peripheral devices should correspond. That is why machine-level languages are machine-dependent languages. But system programmers use machine-level languages for writing programs that must be as fast and efficient as possible.

Exercise 1. Read the text and discuss these questions:

1. How can we define programming languages?

2. Why do we need programming languages?

3. Is the function of the programming languages so important?

4. How can we explain the difference between the natural languages and programming languages?

5. What languages aren’t usually considered programming languages?

6. Why should programming languages possess a greater degree of preciseness and completeness than human languages?

7. What is the difference between high-level languages and machine-level languages?