The ALGOL Programming Language
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ALGOL (ALGOrithmic Language) is one of several high level languages designed specifically for programming scientific computations. It started out in the late 1950's, first formalized in a report titled ALGOL 58, and then progressed through reports ALGOL 60, and ALGOL 68. It was designed by an international committee to be a universal language. Their original conference, which took place in Zurich, was one of the first formal attempts to address the issue of software portability. ALGOL's machine independence permitted the designers to be more creative, but it made implementation much more difficult.
Although ALGOL never reached the level of commercial popularity of FORTRAN and COBOL, it is considered the most important language of its era in terms of its influence on later language development. ALGOL’s lexical and syntactic structures became so popular that virtually all languages designed since have been referred to as "ALGOL - like"; that is they have been hierarchical in structure with nesting of both environments and control structures.
Significant Language Features
ALGOL was the first second-generation programming language and its characteristics are typical of the entire generation. First consider the data structures, which are very close to first generation structures. In ALGOL 60 the block structure was introduced: the ability to create blocks of statements for the scope of variables and the extent of influence of control statements. Along with that, two different means of passing parameters to subprograms; call by value and call by name.
Structured control statements: if - then - else and the use of a general condition for iteration control were also features, as was the concept of recursion: the ability of a procedure to call itself.
One of the greatest impacts ALGOL 60 had was a result of its description as found in Naur (1963). A major contribution of this report was the introduction of BNF notation for defining the syntax of the language. Overall, ALGOL is considered to be perhaps the most orthogonal programming language, meaning it has a relatively small number of basic constructs and a set of rules for combining those constructs. Every construct has a type associated with it and there are no restrictions on those types. In addition, most constructs produce values.
Several of ALGOL’s other characteristics are listed below:
Areas of Application
ALGOL was used mostly by research computer scientists in the United States and in Europe. Its use in commercial applications was hindered by the absence of standard input/output facilities in its description and the lack of interest in the language by large computer vendors. ALGOL 60 did however become the standard for the publication of algorithms and had a profound effect on future language development.
Sample Program:
Source Code:
// the main program (this is a comment)
BEGIN
FILE F (KIND=REMOTE);
EBCDIC ARRAY E [0:11];
REPLACE E BY "HELLO WORLD!";
WHILE TRUE DO
BEGIN
WRITE (F, *, E);
END;
END.
This program demonstrates the text output function of the ALGOL programming language by displaying the message "Hello world!". This code runs on a Unisys (Burroughs) A-series mainframe.
This program has NOT been tested due to the inability to locate the necessary compiler. It is posted here just to give you an example of what ALGOL source code looks like. Compare it to the other example listed to see the syntactic differences that exist in the language.
