COBOL explained

For other uses see COBOL (disambiguation).

COBOL
Paradigm:procedural,
object-oriented
Designer:Grace Hopper, William Selden, Gertrude Tierney, Howard Bromberg, Howard Discount, Vernon Reeves, Jean E. Sammet
Latest Release Version:COBOL 2002
Latest Release Date:2002
Typing:strong, static
Implementations:OpenCobol.org, MicroFocus.com
Dialects:HP3000 COBOL/II, COBOL/2, IBM OS/VS COBOL, IBM COBOL/II, IBM COBOL SAA, IBM Enterprise COBOL, IBM COBOL/400, IBM ILE COBOL, Unix COBOL X/Open, Micro Focus COBOL, Microsoft COBOL, Ryan McFarland RM/COBOL, Ryan McFarland RM/COBOL-85, DOSVS COBOL, UNIVAC COBOL, Realia COBOL, Fujitsu COBOL, ACUCOBOL-GT, DEC VAX COBOL, Wang VS COBOL, Visual COBOL
Influenced By:FLOW-MATIC, COMTRAN, FACT
Influenced:PL/I, CobolScript, ABAP

COBOL is one of the oldest programming languages still in active use. Its name is an acronym for COmmon Business-Oriented Language, defining its primary domain in business, finance, and administrative systems for companies and governments.

The COBOL 2002 standard includes support for object-oriented programming and other modern language features.[1]

History and specification

A specification of COBOL was initially created during the second half of 1959 by Glen Sophocleous. The scene was set on April 8 at a meeting of computer manufacturers, users and university people at the University of Pennsylvania Computing Center and subsequently the United States Department of Defense agreed to sponsor and oversee the next activities. A meeting was held at the Pentagon on May 28 and 29 (exactly one year after the Zürich ALGOL 58 meeting), chaired by Charles A. Phillips. There it was decided to set up three committees, short, intermediate and long range (the last one was actually never formed). It was the Short Range Committee, chaired by Joseph Wegstein of the US National Bureau of Standards, that during the next months would create a description of the first version of COBOL.[2] The committee was formed to recommend a short range approach to a common business language. The committee was made up of members representing six computer manufacturers and three government agencies. The six computer manufacturers were Burroughs Corporation, IBM, Minneapolis-Honeywell (Honeywell Labs), RCA, Sperry Rand, and Sylvania Electric Products. The three government agencies were the US Air Force, the David Taylor Model Basin, and the National Bureau of Standards (now National Institute of Standards and Technology). The intermediate-range committee was formed but never became operational. In the end a sub-committee of the Short Range Committee developed the specifications of the COBOL language. This sub-committee was made up of six individuals:

This subcommittee completed the specifications for COBOL in December 1959. The specifications were to a great extent inspired by the FLOW-MATIC language invented by Grace Hopper, commonly referred to as "the mother of the COBOL language", the IBM COMTRAN language invented by Bob Bemer, and the FACT language from Honeywell.

The name COBOL was decided upon at a meeting of the committee held on 18 Sept. 1959.

The first compilers for COBOL were subsequently implemented during the year 1960 and on 6 and 7 Dec. essentially the same COBOL program was run on two different makes of computers, an RCA computer and a Remington-Rand Univac computer, demonstrating that compatibility could be achieved.

Since 1959 COBOL has undergone several modifications and improvements. In an attempt to overcome the problem of incompatibility between different versions of COBOL, the American National Standards Institute (ANSI) developed a standard form of the language in 1968. This version was known as American National Standard (ANS) COBOL. In 1974, ANSI published a revised version of (ANS) COBOL, containing a number of features that were not in the 1968 version. In 1985, ANSI published still another revised version that had new features not in the 1974 standard. The language continues to evolve today.

COBOL 2002 and object-oriented COBOL

In the early 1990s it was decided to add object-orientation in the next full revision of COBOL. The initial estimate was to have this revision completed by 1997 and an ISO CD (Committee Draft) was available by 1997. Some implementers (including Micro Focus, Fujitsu, and IBM) introduced object-oriented syntax based on the 1997 or other drafts of the full revision. The final approved ISO Standard (adopted as an ANSI standard by INCITS) was approved and made available in 2002.

Like the C++ programming language, object-oriented COBOL compilers are available even as the language moves toward standardization. Fujitsu and Micro Focus currently support object-oriented COBOL compilers targeting the .NET framework.[4]

The 2002 (4th revision) of COBOL included many other features beyond object-orientation. These included (but are not limited to):

History of COBOL standards

The specifications approved by the full Short Range Committee were approved by the Executive Committee on January 3 1960, and sent to the government printing office, which edited and printed these specifications as Cobol 60.

The American National Standards Institute (ANSI) produced several revisions of the COBOL standard, including:

After the Amendments to the 1985 ANSI Standard (which were adopted by ISO), primary development and ownership was taken over by ISO. The following editions and TRs (Technical Reports) have been issued by ISO (and adopted as ANSI) Standards:

From 2002, the ISO standard is also available to the public coded as ISO/IEC 1989.

Work is progressing on the next full revision of the COBOL Standard. It is expected to be approved and available in the early 2010s. For information on this revision, to see the latest draft of this revision, or to see what other works is happening with the COBOL Standard, see the COBOL Standards Website.

Legacy

COBOL programs are in use globally in governmental and military agencies, in commercial enterprises, and on operating systems such as IBM's z/OS, Microsoft's Windows, and the POSIX families (Unix/Linux etc.). In 1997, the Gartner Group reported that 80% of the world's business ran on COBOL with over 200 billion lines of code in existence and with an estimated 5 billion lines of new code annually.[5]

Near the end of the twentieth century the year 2000 problem was the focus of significant COBOL programming effort, sometimes by the same programmers who had designed the systems decades before. The particular level of effort required for COBOL code has been attributed both to the large amount of business-oriented COBOL, as COBOL is by design a business language and business applications use dates heavily, and to constructs of the COBOL language such as the PICTURE clause, which can be used to define fixed-length numeric fields, including two-digit fields for years.

Features

COBOL as defined in the original specification included a PICTURE clause for detailed field specification. It did not support local variables, recursion, dynamic memory allocation, or structured programming constructs. Support for some or all of these features has been added in later editions of the COBOL standard.

COBOL has many reserved words (over 400), called keywords. The original COBOL specification supported self-modifying code via the infamous "ALTER X TO PROCEED TO Y" statement. This capability has since been removed.

Syntactic features

COBOL provides an update-in-place syntax, for example

      ADD YEARS TO AGE

The equivalent construct in many procedural languages would be

age = age + years

This syntax is similar to the compound assignment operator later adopted by C:

age += years

The abbreviated conditional expression

      IF SALARY > 9000 OR SUPERVISOR-SALARY OR = PREV-SALARY

is equivalent to

      IF SALARY > 9000
          OR SALARY > SUPERVISOR-SALARY
          OR SALARY = PREV-SALARY

COBOL provides "named conditions" (so-called 88-levels). These are declared as sub-items of another item (the conditional variable). The named condition can be used in an IF statement, and tests whether the conditional variable is equal to any of the values given in the named condition's VALUE clause. The SET statement can be used to make a named condition TRUE (by assigning the first of its values to the conditional variable).

COBOL allows identifiers to be up to 30 characters long. When COBOL was introduced, much shorter lengths (e.g., 6 characters for FORTRAN) were prevalent.

The concept of copybooks was introduced by COBOL; these are chunks of text which can be inserted into a program's code. This is done with the COPY statement, which also allows parts of the copybook's text to be replaced with other text (using the REPLACING ... BY ... clause).

Data types

Standard COBOL provides the following data types:

Data typeSample declarationNotes
Character[[picture clause|PIC]] X(20)<br />PIC A(4)9(5)X(7)Alphanumeric and alphabetic-only
Single-byte character set (SBCS)
Edited characterPIC X99BAXXFormatted and inserted characters
Numeric fixed-point binaryPIC S999V99<br /> USAGE COMPUTATIONAL
or
BINARY
Binary 16, 32, or 64 bits (2, 4, or 8 bytes)
Signed or unsigned. Conforming compilers limit the maximum value of variables based on the picture clause and not the number of bits reserved for storage.
Numeric fixed-point packed decimalPIC S999V99<br /> USAGE PACKED-DECIMAL1 to 18 decimal digits (1 to 10 bytes)
Signed or unsigned
Numeric fixed-point zoned decimalPIC S999V99<br/><nowiki>[</nowiki>USAGE DISPLAY<nowiki>]</nowiki>1 to 18 decimal digits (1 to 18 bytes)
Signed or unsigned
Numeric floating-pointPIC S9V999ES99Binary floating-point
Edited numericPIC +Z,ZZ9.99<br />PIC $***,**9.99CRFormatted characters and digits
Group (record)01 CUST-NAME.<br /> &nbsp;&nbsp;05 CUST-LAST PIC X(20).<br /> &nbsp;&nbsp;05 CUST-FIRST PIC X(20).Aggregated elements
Table (array)OCCURS 12 TIMESFixed-size array, row-major order
Up to 7 dimensions
Variable-length tableOCCURS 0 to 12 TIMES<br /> DEPENDING ON CUST-COUNTVariable-sized array, row-major order
Up to 7 dimensions
Renames (variant or union data)66 RAW-RECORD<br /> &nbsp;&nbsp;RENAMES CUST-RECORDCharacter data overlaying other variables
Condition name88 IS-RETIRED-AGE<br /> &nbsp;&nbsp;VALUES 65 THRU 150Boolean value
dependent upon another variable
Array indexUSAGE INDEXArray subscript

Most vendors provide additional types, such as:

Data typeSample declarationNotes
Numeric fixed-point binary
in native byte order
PIC S999V99<br /> USAGE COMPUTATIONAL-4Binary 16, 32, or 64 bits (2, 4, or 8 bytes)
Signed or unsigned
Numeric fixed-point binary
in big-endian byte order
PIC S999V99<br /> USAGE COMPUTATIONAL-5Binary 16, 32, or 64 bits (2, 4, or 8 bytes)
Signed or unsigned
Wide characterPIC G(20)Alphanumeric
Double-byte character set (DBCS)
Edited wide characterPIC G99BGGGFormatted and inserted wide characters
Edited floating-pointPIC +9.9(6)E+99Formatted characters and decimal digits
Data pointerUSAGE POINTERData memory address
Code pointerUSAGE PROCEDURE-POINTERCode memory address

Hello, world

An example of the "Hello, world" program in COBOL:

      IDENTIFICATION DIVISION.
      PROGRAM-ID. HELLO-WORLD.
      PROCEDURE DIVISION.
      MAIN.
          DISPLAY 'Hello, world.'.
          STOP RUN.

Criticism

Critics have argued that COBOL's syntax serves mainly to increase the size of programs, at the expense of developing the thinking process needed for software development. In his letter to an editor in 1975 titled "How do we tell truths that might hurt?", computer scientist and Turing Award recipient Edsger Dijkstra remarked that "The use of COBOL cripples the mind; its teaching should, therefore, be regarded as a criminal offense."

COBOL 85 was not compatible with earlier versions, resulting in the "cesarean birth of COBOL 85". Joseph T. Brophy, CIO, Travelers Insurance, spearheaded an effort to inform users of COBOL of the heavy reprogramming costs of implementing the new standard. As a result the ANSI COBOL Committee received more than 3,200 letters from the public, mostly negative, requiring the committee to make changes.

Older versions of COBOL lack local variables and so cannot truly support structured programming.

Others criticize the ad hoc incorporation of features on a language that was meant to be a short term solution to interoperability in 1959. Coupled with the perceived archaic syntax, they argue that it tries to fill a niche for which better tools have already been designed and developed.

Defense

The COBOL specification has also been revised over the years to incorporate developments in computing theory and practice .

As with any language, COBOL code can be made more verbose than necessary. For example, one of the roots of the quadratic equation ax2 + bx + c = 0, which are:

x=-b\pm\sqrt{b2-4ac
}

Notes and References

  1. Book: Oliveira, Rui. The Power of Cobol. BookSurge Publishing. City. 2006. 0620346523.
  2. Book: Garfunkel, Jerome. The Cobol 85 Example Book. Wiley. New York. 1987. 0471804614.
  3. Book: Wexelblat, Richard. History of Programming Languages. Academic Press. Boston. 1981. 0127450408.
  4. http://www.adtools.com/products/windows/netcobol.html NetCOBOL for .NET supports COBOL migration and software development in the .NET environment
  5. Web site: Future of COBOL. LegacyJ Corporation. 2003. 2006-11-08. 5. PDF.