What is COBOL ? .. Introduction Tutorial

COBOL is a high-level programming language first developed by the CODASYL Committee (Conference on Data Systems Languages) in 1960. Since then, responsibility for developing new COBOL standards has been assumed by the American National Standards Institute (ANSI).

Three ANSI standards for COBOL have been produced: in 1968, 1974 and 1985. A new COBOL standard introducing object-oriented programming to COBOL, is due within the next few years.

The word COBOL is an acronym that stands for COmmon Business Oriented Language. As the the expanded acronym indicates, COBOL is designed for developing business, typically file-oriented, applications. It is not designed for writing systems programs. For instance you would not develop an operating system or a compiler using COBOL.

COBOL is self-documenting
One of the design goals for COBOL was to make it possible for non-programmers such as supervisors, managers and users, to read and understand COBOL code. As a result, COBOL contains such English-like structural elements as verbs, clauses, sentences, sections and divisions. As it happens, this design goal was not realized. Managers and users nowadays do not read COBOL programs. Computer programs are just too complex for most laymen to understand them, however familiar the syntactic elements. But the design goal and its effect on COBOL syntax has had one important side-effect. It has made COBOL the most readable, understandable and self-documenting programming language in use today. It has also made it the most verbose.

It is easy for programmers unused to the business programming paradigm, where programming with a view to ease of maintenance is very important, to dismiss the advantage that COBOL’s readability imparts. Not only does this readability generally assist the maintenance process but the older a program gets the more valuable this readability becomes.

When programs are new, both the in-program comments and the external documentation accurately reflect the program code. But over time, as more and more revisions are applied to the code, it gets out of step with the documentation until the documentation is actually a hindrance to maintenance rather than a help. The self-documenting nature of COBOL means that this problem is not as severe with COBOL programs as it is with other languages

Readers who are familiar with C or C++ or Java might want to consider how difficult it becomes to maintain programs written in these languages. C programs that you have written yourself are difficult enough to understand when you come back to them six months later. Consider how much more difficult it would be to understand a program that had been written fifteen years previously, by someone else, and which had since been amended and added to by so many others that the documentation no longer accurately reflects the program code. This is a nightmare still awaiting maintenance programmers of the future

COBOL is simple
COBOL is a simple language (no pointers, no user defined functions, no user defined types) with a limited scope of function. It encourages a simple straightforward programming style. Curiously enough though, despite its limitations, COBOL has proven itself to be well suited to its targeted problem domain (business computing). Most COBOL programs operate in a domain where the program complexity lies in the business rules that have to be encoded rather than in the sophistication of the data structures or algorithms required. And in cases where sophisticated algorithms are required COBOL usually meets the need with an appropriate verb such as the SORT and the SEARCH.

We noted above that COBOL is a simple language with a limited scope of function. And that is the way it used to be but the introduction of OO-COBOL has changed all that. OO-COBOL retains all the advantages of previous versions but now includes -

User Defined Functions
Object Orientation
National Characters – Unicode
Multiple Currency Symbols
Cultural Adaptability (Locales)
Dynamic Memory Allocation (pointers)
Data Validation Using New VALIDATE Verb
Binary and Floating Point Data Types
User Defined Data Types

COBOL is non-proprietary (portable)
The COBOL standard does not belong to any particular vendor. The vendor independent ANSI COBOL committee legislates formal, non-vendor-specific syntax and semantic language standards. COBOL has been ported to virtually every hardware platform – from every favour of Windows, to every falser of Unix, to AS/400, VSE, OS/2, DOS, VMS, Unisys, DG, VM, and MVS.

COBOL is Maintainable
COBOL has a 30 year proven track record for application maintenance, enhancement and production support at the enterprise level. Early indications from the year 2000 problem are that COBOL applications were actually cheaper to fix than applications written in more recent languages.

One reason for the maintainability of COBOL programs has been given above – the readability of COBOL code. Another reason is COBOL’s rigid hierarchical structure. In COBOL programs all external references, such as to devices, files, command sequences, collating sequences, the currency symbol and the decimal point symbol, are defined in the Environment Division.
When a COBOL program is moved to a new machine, or has new peripheral devices attached, or is required to work in a different country; COBOL programmers know that the parts of the program that will have to be altered to accommodate these changes will be isolated in the Environment Division. In other programming languages, programmer discipline could have ensured that the references liable to change were restricted to one part of the program but they could just as easily be spread throughout the program. In COBOL programs, programmers have no choice. COBOL’s rigid hierarchical structure ensures that these items are restricted to the Environment Division.

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