Pascal
Pascal is a high-level programming language, which is named after Blaise Pascal, a seventeenth century French mathematician who constructed one of the first mechanical adding machines. The language was developed by Niklaus Wirth in 1971. It resembles ALGOL, a now little used language devised for scientific computing
The person for whom Pascal is named, Blaise Pascal, lived from 1623 to 1662. He was a child prodigy and accomplished mathematician. In 1642, at 21 years of age, he invented a calculation machine. Pascal is credited with the discovery of the mathematical theory of probability. He also made fundamentally important contributions to number theory, geometry, and the advancement of scientific theory in the face of religious criticism.
A programming language contains a vocabulary, certain keywords and set of grammatical rules for instructing a computer to perform specific tasks. A high level programming language like Pascal is more or less independent of any particular type of computer. Also, the language uses English type statements that are converted to machine statements, which provide the computer with the instructions for a particular action.
Since 1971 many versions of Pascal have emerged, including versions by Borland, Inc. (Turbo Pascal), Microsoft (Quick Pascal), and Apple, Inc. (Macintosh Pascal). Pascal is a general purpose programming language, which enjoyed great popularity throughout the 1970s and the 1980s. Today, it remains a popular teaching tool.
The popularity of Pascal can be attributed in large measure to two things. First, in the early 1980's, the Educational Testing Service, the company that creates the primary college entrance exam in the United States, added a Computer Service exam to the placement exams taken by high school students. The computer language chosen was Pascal (it remained the choice until 1999). Thus, many students were of necessity exposed to Pascal programming. Secondly, the Borland International company marketed the Turbo Pascal compiler. The compiler was revolutionary because of its speed--a compilation rate of several thousand lines per minute. The benefit of speed made many users gravitate to the use of Pascal.
Pascal is best known for its high performance with structured programming techniques. Because the language is very data-oriented, the structure is imposed to prevent the mix up of data types. Even though Pascal reads very much like a natural language, the rigid structure of the language forces programmers to write programs that are methodically and carefully designed. This rigidity is one feature that has made it a popular teaching language. Another feature of Pascal is that it highlights concepts that are similar to all computer languages. So, learning Pascal makes the learning of other languages easier. Also, Pascal uses standardized language, which makes the writing of programs less arduous.
However, Pascal success in other spheres, such as a business tool, was not as pervasive due to the inflexibility of the language and the dearth of application development tools. In other applications too, Pascal has been supplanted by other languages, such a C, C++ and Java. To address some of the criticisms against Pascal, Wirth designed a new language called Modula-2. Modula-2 is similar to Pascal, but contains additional features enabling the separate compilation of program routines and multitasking.
In order to create a functional Pascal program, an editor, compiler and linker are needed. The editor create the Pascal source code. The compiler converts this source code to a machine readable form known as the object code. A number of compilers are marketed, such as Turbo Pascal. Finally, the linker functions to link the object code to create the executable code.
Pascal is comprised of simple text files, just like regular ASCI files, that contain so-called program statements. They are created using a text editor--a program, such as EMACA, that enables the user to create and edit text files. These files are also called the source program, and are denoted with the file extension ".pas" or ".p.". The text must then be compiled to turn it into a file capable of generating an action. Pascal programs can be compiled using the compiler called pc.
The basic format of every Pascal program is the same. The "PROGRAM" is always the first word of a Pascal program and is a keyword. The designation "TITLE" refers to the name that the programmer gives to the program. It is an identifier. There are rules concerning the format and length of the identifier. The "INPUT/OUTPUT" statement states what the program will do. Data is inputted from the keyboard and outputted to the screen. The begin statement defines the starting point of the program and provides a means of grouping statements together. All statements that are between the begin and end commands are considered part of the same group or block. The end statement must always be the final statement
A recent Pascal innovation is a revitalized system for the Windows operating environment. Called Delphi, the system's graphical design tools permit a much more rapid assembly of graphical interfaces than is possible using the C and C++ programming languages.
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