Cobol

An algorithmic language oriented towards problems of data processing (COBOL is an acronym for COmmon Business Oriented Language). The method of writing a program is close to natural English and is convenient for the study, documentation and transportation of the program from one computer to another. Cobol was developed in the U.S.A. starting in 1959; it has spread widely and has become a national standard [1]. The Russian version of Cobol was published in 1968 [2] and in 1978 the State standard was introduced [3].

A source program in Cobol consists of four divisions:

1) The identification division contains the names of the program and the author, the date and other reference information.

2) The enviroment division defines the configuration of the compiler and of the object computer, of the special hardware characteristics and of the input-output control.

3) The data division contains a machine-independent description of the type and structure of the input, intermediate and output data. Numerical and non-numerical elementary data are allowed, which can be combined into groups, groups of groups, etc. This structural hierarchy is defined by numbers of levels. The highest level is assigned to a logical record. The collections of homogeneous or heterogeneous records form files. Directions are admissible when they increase the effectiveness of the internal interpretation of the data format.

4) The procedure division defines the data processing operations. It has the form of a sequence of statements, named paragraphs and sections, containing imperative statements, conditional statements and compiler-directing statements.

According to their purpose, the elements of Cobol are divided into a nucleus and 11 functional processing modules. The nucleus contains the elements of the language necessary for data processing in the internal memory of the computer. The functional modules contain, respectively, means of: table handling; access, random access and indexed input-output for the organization of the external file access; sorting-merging; output report writing; segmentation of the program for overlaying during execution time; modification of texts in Cobol from a library; and inclusion of them into the program debugging and control of data and procedures; organization of inter-program communications with other programs; and also a communication facility for transmitting and receiving messages.

The flexibility of choice of standard subsets of Cobol for specific compiler implementations is based on distinguishing some fixed levels in the nucleus and the functional modules. The elements of the language are arranged in levels, so that the higher levels ensure a more complete realization of the corresponding function and contain the lower levels as proper subsets. Some functional modules contain, as their lowest level, a null set.

The main directions of subsequent development of Cobol have been the organization of interaction with data bases and the use of ideas from structured programming.

References

[1]	, American National Standard. Programming language COBOL , ANSI X3.23 , ANSI (1974)
[2]	L.P. Babenko, et al., "Algorithmic languages" , Proc. 1-st All-union Conf. Programming , Kiev (1968) pp. 3–15 (In Russian)
[3]	, The programing language COBOL , GOST 22558–77 (In Russian)
[4]	E.L. Yushchenko, et al., "COBOL" , Kiev (1974) (In Russian)