COBOL

From Wikipedia, the free encyclopedia

 This article needs additional citations for verification.
Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (February 2007)
COBOL
Paradigm procedural,
object-oriented
Appeared in 1959
Designed by Grace Hopper, William Selden, Gertrude Tierney, Howard Bromberg, Howard Discount, Vernon Reeves, Jean E. Sammet
Typing discipline strong, static
Major implementations http://www.opencobol.org/
Dialects 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
Influenced by FLOW-MATIC, COMTRAN
Influenced PL/I

COBOL (pronounced /ˈkoʊbɒl/) 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]

Contents

[edit] History and specification

COBOL was initially created in 1959 by The Short Range Committee, one of three committees proposed at a meeting held at the Pentagon on May 28 and 29, 1959, organized by Charles Phillips of the United States Department of Defense (exactly one year after the Zürich ALGOL 58 meeting).[2] The Short Range Committee was formed to recommend a short range approach to a common business language. It 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). This committee was chaired by a member of the NBS. An Intermediate-Range Committee and a Long-Range Committee were proposed at the Pentagon meeting as well. However although the Intermediate Range Committee was formed, it was never operational; and the Long-Range Committee was never even formed. 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 as the year of 1959 concluded. 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", and the IBM COMTRAN language invented by Bob Bemer.

COBOL (COmmon Business Oriented Language) was one of the earliest high-level programming languages. It was developed in 1959 by a group of computer professionals called the Conference on Data Systems Languages (CODASYL). Since 1959 it 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. Object-oriented COBOL is a subset of COBOL 97, which is the fourth edition in the continuing evolution of ANSI/ISO standard COBOL. COBOL 97 includes conventional improvements as well as object-oriented features. Like the C++ programming language, object-oriented COBOL compilers are available even as the language moves toward standardization.

[edit] 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) has since produced several revisions of the COBOL standard, including

  • COBOL-68
  • COBOL-74
  • COBOL-85
  • COBOL 2002

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

[edit] Defining 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.

[edit] 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.[4]

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.

[edit] Hello, world

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

[edit] 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".[5]

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.[6]

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.

[edit] Defense

Advocates claim that typically those who criticize the language have never been COBOL programmers and often misrepresent it. Critic Edsger Dijkstra was also positively impressed by Michael A. Jackson's ideas about "Structured Programming" in COBOL (Jackson Structured Programming).[citation needed]

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=\frac{-b \pm \sqrt {b^2-4ac\ }}{2a} ,

can be coded in COBOL using the "compute" verb as:

      COMPUTE X = (-B + (B ** 2 - (4 * A * C)) ** .5) / (2 * A)

The same formula could also be written less concisely as:

      MULTIPLY B BY B GIVING B-SQUARED.  
      MULTIPLY 4 BY A GIVING FOUR-A.  
      MULTIPLY FOUR-A BY C GIVING FOUR-A-C.  
      SUBTRACT FOUR-A-C FROM B-SQUARED GIVING RESULT-1.  
      COMPUTE RESULT-2 = RESULT-1 ** .5.
      SUBTRACT B FROM RESULT-2 GIVING NUMERATOR.
      MULTIPLY 2 BY A GIVING DENOMINATOR.
      DIVIDE NUMERATOR BY DENOMINATOR GIVING X.

Which form to use is a matter of style. In some cases the less concise form may be easier to read. For example:

      ADD YEARS TO AGE.
      MULTIPLY PRICE BY QUANTITY GIVING COST.
      SUBTRACT DISCOUNT FROM COST GIVING FINAL-COST.

Older versions of COBOL supported local variables via embedded programs (scope-delimited by the keywords PROGRAM-ID and END-PROGRAM). Variables declared within the embedded program are invisible outside its scope. Also, local variables could be accomplished via separately compiled sub-programs. Newer COBOL compilers support the LOCAL-STORAGE section for local variables.

[edit] 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 > 80000 OR SUPERVISOR-SALARY OR = PREV-SALARY

is equivalent to

      IF SALARY > 80000 OR SALARY > SUPERVISOR-SALARY OR SALARY = PREV-SALARY

COBOL provides "named conditions" (so-called 88-levels).

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.

[edit] Data types

Standard COBOL provides the following data types:

Data type Sample declaration Notes
Character PIC X(20)
PIC A(4)9(5)X(7)		 Alphanumeric and alphabetic-only
Single-byte character set (SBCS)
Edited character PIC X99BAXX Formatted and inserted characters
Numeric fixed-point binary PIC S999V99
USAGE COMPUTATIONAL		 Binary 16, 32, or 64 bits (2, 4, or 8 bytes)
Signed or unsigned
Numeric fixed-point packed decimal PIC S999V99
USAGE PACKED-DECIMAL		 1 to 18 decimal digits (1 to 10 bytes)
Signed or unsigned
Numeric fixed-point zoned decimal PIC S999V99 1 to 18 decimal digits (1 to 18 bytes)
Signed or unsigned
Numeric floating-point PIC S9V999ES99 Binary floating-point
Edited numeric PIC +Z,ZZ9.99
PIC $***,**9.99CR		 Formatted characters and digits
Group (record) 01 CUST-NAME.
  05 CUST-LAST PIC X(20).
  05 CUST-FIRST PIC X(20).		 Aggregated elements
Table (array) OCCURS 12 TIMES Fixed-size array, row-major order
Up to 7 dimensions
Variable-length table OCCURS 0 to 12 TIMES
DEPENDING ON CUST-COUNT		 Variable-sized array, row-major order
Up to 7 dimensions
Renames (variant or union data) 66 RAW-RECORD
  RENAMES CUST-RECORD		 Character data overlaying other variables
Condition name 88 IS-RETIRED-AGE
  VALUES 65 THRU 150		 Boolean value
dependent upon another variable
Array index USAGE INDEX Array subscript

Most vendors provide additional types, such as:

Data type Sample declaration Notes
Numeric fixed-point binary
in native byte order		 PIC S999V99
USAGE COMPUTATIONAL-4		 Binary 16, 32, or 64 bits (2, 4, or 8 bytes)
Signed or unsigned
Numeric fixed-point binary
in big-endian byte order		 PIC S999V99
USAGE COMPUTATIONAL-5		 Binary 16, 32, or 64 bits (2, 4, or 8 bytes)
Signed or unsigned
Wide character PIC G(20) Alphanumeric
Double-byte character set (DBCS)
Edited wide character PIC G99BGGG Formatted and inserted wide characters
Edited floating-point PIC +9.9(6)E+99 Formatted characters and decimal digits
Data pointer USAGE POINTER Data memory address
Code pointer USAGE PROCEDURE-POINTER Code memory address

[edit] Aphorisms and humor about COBOL

It has been said of languages like C, C++, and Java that the only way to modify legacy code is to rewrite it - write once and write once again; or write once and throw away. On the other hand, it has been said of COBOL that there actually is one original COBOL program, and it has only been copied and modified millions of times.

The name "ADD 1 TO COBOL GIVING COBOL" has been suggested for a hypothetical object-oriented dialect of COBOL, as a play on the name C++. While this is meant to suggest that COBOL is inherently verbose, the form given is more verbose than COBOL actually requires; the succinct form would be "ADD 1 TO COBOL".

Another suggested name is "POSTINCREMENT COBOL BY 1", which not only reflects the verbose nature of COBOL statements, but also highlights the tendency for COBOL features to require their own dedicated reserved keywords (standard COBOL employs over 400 reserved words), this example being the case for a hypothetical new POSTINCREMENT operator.

[edit] COBOL 2002 and object-oriented COBOL

The COBOL2002 standard supports Unicode, XML generation and parsing, calling conventions to and from non-COBOL languages such as C, and support for execution within framework environments such as Microsoft's .NET and Java (including COBOL instantiated as Enterprise JavaBeans). However, no vendor has yet produced a completely conforming compiler.[7]

[edit] See also

[edit] Other third-generation programming languages

[edit] Other

[edit] References

  1. ^ Oliveira, Rui (2006). The Power of Cobol. City: BookSurge Publishing. ISBN 0620346523. 
  2. ^ Garfunkel, Jerome (1987). The Cobol 85 Example Book. New York: Wiley. ISBN 0471804614. 
  3. ^ Wexelblat, Richard (1981). History of Programming Languages. Boston: Academic Press. ISBN 0127450408. 
  4. ^ Future of COBOL (PDF) 5. LegacyJ Corporation (2003). Retrieved on 2006-11-08.
  5. ^ Dijkstra (2006). E. W. Dijkstra Archive: How do we tell truths that might hurt? (EWD498) (English). University of Texas at Austin. Retrieved on August 29, 2007.
  6. ^ (The COBOL 85 Example Book)
  7. ^ Stern, Nancy (2003). Cobol for the 21st Century. New York: Wiley. ISBN 0471073210. 

[edit] Sources

  • Ebbinkhuijsen, Wim B.C., COBOL Alphen aan den Rijn/Diegem: Samson Bedrijfsinformatie bv, 1990. ISBN 90-14-04560-3. (Dutch)

[edit] External links

Wikibooks
Wikibooks has more on the topic of