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A computer carries out the instructions given in "absolute" machine languages. But people-programmers don't write programs in machine languages, but in programming languages – i.e., the tools, programmers use to create programs, just as English and other spoken languages are the tools writers use to create books. Perhaps the first thing we need to know is the distinction between assembly languages and all other programming languages, collectively called high-level languages.

Writing a program in the assembly language is an exceedingly long and tedious process – a medium-sized program has about 20,000 machine-language instructions in it. A large and complex program can consist of hundreds of thousands of separate machine-language instructions, high-level languages are designed to eliminate the tedium and error-prone nature of assembly language by letting the computer do itself much of the work of generating the detailed machine-language instructions. Assembly languages and high-level languages have their own benefits and drawbacks. There are literally hundreds of programming languages and easily dozens that are used on the PC - the most important are BASIC, Pascal, C and d BASE.

BASIC is the closest thing we have so far to a universal language for personal computers. Its strength is that it is easy to fiddle with and includes features that give us easy access to most of the PC family's spe­cial features, such as the capability to play music on the computer's speaker. Two other well-known languages that are well-suited for profes­sional programming are Pascal and C. Both have the features that are considered most useful in helping programmers create well-crafted pro­grams that are reliable and easy to update. Pascal and C have many similarities, including structural features that promote good programming practices. Pascal finds its champions among those who have studied it in school. It is the language most favored for teaching computer science, and it was originally created as a language for teaching, rather than for professional use. C is favored by the programmers who are looking for the utmost efficiency in this language, for writing programs that need to be tight and efficient.

Usually a programming language is chosen on very pragmatic ground: which languages the programmer already knows (or can easily learn) and how well suited the programming language into the work that the program has to accomplish. Personal taste and convenience also play a major part in the selection of a programming language and why shouldn't they?

The last group of programming languages are application languages – the integral part of major application programs. Individually each of the application languages is a whole world “into” itself. Probably, the most widely known and used kind of application languages is the spreadsheet, which allows to set up and stove commands that can be used over and over again, which is the essence of what a programming language is. A spreadsheet is much more specialized programming language than other languages, because it has to work within its own spreadsheet context.

As artificial intelligence (AI) evolved, it has produced specific pro­grams that solve specific kinds of programs and a set of tools that help one construct other program-solving programs. By the end of 1950 it was recognized that the standard programming languages of the time, which had been designed to support a primarily numeric processing, were not very effective in supporting the nonnumeric symbolic comput­ing that AI programs do. LISP – a language designed for symbolic com­puting, particularly list processing, had appeared by 1960. LISP still serves (although in several greatly extended forms) as the basis for most AI program development. LISP is an interpreted language, although compilers for it are available as well. But when it is run interpretively, it supports significant interactive symboling debugging.

In recent years other kinds of AI languages have emerged. Prolog – is a language whose main control structure is not the sequential execution of a set of statements, but rather the application of a specific inference mechanism to the program, which is actually a set of logical assertions. Prolog has been designed to exploit the communicational possibilities associated with the sequential execution of programs.