COBOL

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This article is about the compiled programming language. For other uses, see COBOL (disambiguation).
COBOL
Paradigm(s) procedural, imperative, object-oriented
Designed by Grace Hopper, William Selden, Gertrude Tierney, Howard Bromberg, Howard Discount, Vernon Reeves, Jean E. Sammet
Appeared in 1959 (1959)
Stable release ISO/IEC 1989:2014 / 2014
Typing discipline strong, static
Major implementations GNU Cobol, Micro Focus International (e.g. the Eclipse-plug-in Micro Focus Net Express)
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, ICL COBOL, ACUCOBOL-GT, isCOBOL, COBOL-IT, DEC COBOL-10, DEC VAX COBOL, Wang VS COBOL, Visual COBOL, Tandem (NonStop) COBOL85, Tandem (NonStop) SCOBOL, Unisys MCP COBOL74, Unisys MCP COBOL85
Influenced by FLOW-MATIC, COMTRAN, AIMACO, FACT
Influenced PL/I, CobolScript, ABAP
Filename extension(s) .cbl, .cob, .cpy

COBOL (/ˈkbɒl/) is a compiled computer programming language designed for business use. It is imperative, procedural and, since 2002, object-oriented. It was designed in 1959 by the Conference on Data Systems Languages (CODASYL) and was largely based on previous programming language design work by Grace Hopper, commonly referred to as "the mother of COBOL".[1][2] COBOL stands for COmmon Business-Oriented Language.

COBOL is primarily used in business, finance, and administrative systems for companies and governments. In 1997, Gartner Group estimated that there were a total of 200 billion lines of COBOL in existence which ran 80% of all business programs.[3]

COBOL was one of the first programming languages to be standardised: the first COBOL standard was issued by ANSI in 1968. The standard has been revised four times since then, with ISO publishing the latest standard as ISO/IEC 1989:2014.[4]

History and specification[edit]

Background[edit]

Computer users and manufacturers were becoming concerned about the rising cost of programming. A 1959 survey had found that in any data processing installation, programming cost at least $800,000 and that translating programs to run on new hardware would cost $600,000. In a time where new programming languages were proliferating at an ever increasing rate, the same survey suggested that if a common business-oriented language were used, conversion would be far cheaper and faster.[5]:282

caption
Grace Hopper, the inventor of FLOW-MATIC.

In 1959, Grace Hopper, inventor of the English-like data processing language FLOW-MATIC, led a group of users and manufacturers to ask the Department of Defense (DoD) to sponsor an effort to create a common, problem-oriented, hardware-independent programming language. The delegation impressed Charles A. Phillips, director of the Data System Research Staff at the DoD, who thought that they "thoroughly understood" the DoD's problems. The DoD operated 225 computers, had a further 175 on order and had spent over $200 million on implementing programs to run on them. Portable programs would save time, reduce costs and ease modernisation.[5]:283

Phillips agreed to sponsor the meeting and tasked the delegation with drafting the agenda.[5]:284

COBOL 60[edit]

On May 28 and 29 of 1959 (exactly one year after the Zürich ALGOL 58 meeting), a meeting was held at the Pentagon to discuss creating a common programming language for business. It was attended by 41 people and was chaired by Phillips.[6] The Department of Defense was concerned about whether it could run the same data processing programs on different computers. FORTRAN, the only mainstream language at the time, lacked the features needed to write such programs.[7]

Representatives enthusiastically described a language which could work in a wide variety of environments, from banking and insurance to utilities and inventory control. They agreed unanimously that more people should be able to program and that the new language should not be restricted by the limitations of contemporary technology. A majority agreed that the language should make maximum use of English, be capable of change, be machine-independent and be easy to use, even at the expense of power.[5]:286

The meeting resulted in the creation of CODASYL and three committees: short-, intermediate- and long-range. The short-range committee was given to September (three months) to produce specifications for an interim language.[8]:ID/9 Their official mission, however, was to identify the strengths and weaknesses of existing programming languages and did not explicitly direct them to create a new language.[7] Betty Holberton, a short-range committee member, described the three month deadline as "gross optimism" and doubted that the language really would be a stopgap.[7]:288

The short-range 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 Navy's David Taylor Model Basin, and the National Bureau of Standards (now the National Institute of Standards and Technology).[9](I.2.1.1) The committee was chaired by Joseph Wegstein of the US National Bureau of Standards.[10]

'And what name do you want inscribed?'
I said, 'I'll write it for you.' I wrote the name down: COBOL.
'What kind of name is that?'
'Well it's a Polish name. We shortened it and got rid of a lot of unnecessary notation.'

Howard Bromberg on how he bought the COBOL tombstone[11]

It soon became apparent that the committee was too large for any progress to be made quickly. A frustrated Howard Bromberg bought a tombstone with "COBOL" engraved on it and sent it to Charles Phillips to demonstrate his displeasure (the tombstone is currently at the Computer History Museum).[11][12] A sub-committee was formed to analyze existing languages and was made up of six individuals:[7][13][5]:289

  • William Selden and Gertrude Tierney of IBM
  • Howard Bromberg and Howard Discount of RCA
  • Vernon Reeves and Jean E. Sammet of Sylvania Electric Products

The sub-committee did most of the work creating the specification, leaving the short-range committee to review and modify their work before producing the finished specification.[7]

The committee mainly investigated the FLOW-MATIC, AIMACO and COMTRAN programming languages.[7][9](I.1.2) The FLOW-MATIC language was particularly influential because it had been implemented and because AIMACO was a derivative of it with only minor changes.[5]:290[14] FLOW-MATIC's inventor, Grace Hopper, served as a technical adviser to the committee.[15]:132

IBM's COMTRAN language invented by Bob Bemer was also drawn upon, but it was regarded as a competitor to FLOW-MATIC[5]:292 by a short-range committee made up of colleagues of Grace Hopper.[5]:296 Some of its features were not incorporated into COBOL so that it would not look like IBM had dominated the design process.[8]:ID/9 When Roy Goldfinger, author of the COMTRAN manual and intermediate-range committee member, attended a subcommittee meeting to support his language and encourage the use of algebraic expressions, Grace Hopper sent a memo to the short-range committee reiterating Sperry Rand's efforts to create a language based on English.[5]:291 In 1980, Grace Hopper commented that "COBOL 60 is 95% FLOW-MATIC" and that COMTRAN had had an "extremely small" influence. Furthermore, she said that she would claim that work was influenced by both FLOW-MATIC and COMTRAN only to "keep other people happy [so they] wouldn't try to knock us out".[16]:37 Features from COMTRAN incorporated into COBOL included an improved IF statement which obviated the need for GO TO's and a more robust file management system.[5]:292

In October, the intermediate-range committee received copies of the FACT language specification created by Roy Nutt. Its features impressed the committee so much that they passed a resolution to base COBOL on it.[5]:293 This was a blow to the short-range committee, who had made good progress on the specification. Despite being technically superior, FACT had not been created with portability in mind or through manufacturer and user consensus, allowing supporters of a FLOW-MATIC-based COBOL to overturn the resolution. RCA representative Howard Bromberg also decided to block FACT so that RCA's work on a COBOL implementation would not go to waste.[5]:294

The name "COBOL" was coined by Bob Bemer.[17][18] The subcommittee completed the specifications for COBOL in December 1959.[9](I.2.1)

The specifications approved by the short-range committee were approved by the Executive Committee on January 3, 1960, and sent to the government printing office, which printed these as COBOL 60. The language's stated objectives were to allow efficient, portable programs to be easily written, to allow users to move to new systems with minimal effort and cost, and to be suitable for inexperienced programmers.[9](I.1.1) The CODASYL Executive Committee later created the COBOL Maintenance Committee to answer questions from users and vendors and to improve and expand the specifications.[19]:47

During 1960, RCA and Sperry Rand worked on creating a COBOL compiler. The first COBOL program was run on 17 August on an RCA 501.[5]:297 On December 6 and 7, the same COBOL program (albeit with minor changes) ran on an RCA computer and a Remington-Rand Univac computer, demonstrating that compatibility could be achieved.[20]

COBOL-61 to COBOL-65[edit]

COBOL 60 was replaced in 1961 by COBOL-61. This was then replaced by the COBOL-61 Extended specifications in 1963 which introduced the sort and report writer facilities.[19]:48 The added facilities fixed flaws identified by Honeywell in late 1959 in a letter to the short-range committee.[5]:297 COBOL, Edition 1965 brought further clarifications to the specifications and introduced facilities for handling mass storage files and tables.[9](I.2.2.4)

COBOL 1968[edit]

Efforts began to standardise COBOL to overcome incompatibilities between versions. In late 1962, both ISO and the United States of America Standards Institute (now ANSI) formed groups to create standards. ANSI produced USA Standard COBOL X3.23 in August 1968 which became the cornerstone for further versions.[9](I.2.3) This version was known as American National Standard (ANS) COBOL.

COBOL 1974[edit]

By 1970, COBOL had become the most widely used programming language in the world.[5]:301

Independently of the ANSI committee, the CODASYL Programming Language Committee was working on improving the language. They described new versions in 1968, 1969, 1970 and 1973, including changes such as new inter-program communication, debugging and file merging facilities as well as improved string-handling and library inclusion features.[19]:49 Although CODASYL was independent of the ANSI committee, the CODASYL Journal of Development was used by ANSI to identify features which were popular enough to warrant implementing.[19]:52 The Programming Language Committee also liaised with ECMA and the Japanese COBOL Standard committee.[19]:49

In 1974, ANSI published a revised version of (ANS) COBOL, containing new features such as file organizations, the DELETE statement[21] and the segmentation module.[22]:16 Deleted features included the NOTE statement, the EXAMINE statement (which was replaced by INSPECT) and the implementer-defined random access module (which was superseded by the new sequential and relative I/O modules). These made up 44 changes which rendered existing statements incompatible with the new standard.[23] The report writer was slated to be removed from COBOL, but was reinstated before the standard was published.[24][25]

COBOL 1985[edit]

In June 1978, work began on revising COBOL-74. The proposed standard (commonly called COBOL-80) differed significantly from the previous one, causing concerns about incompatibility and conversion costs. In January 1981, Joseph T. Brophy, Senior Vice-President of Travelers Insurance, threatened to sue the standard committee because it was not upwards compatible with COBOL-74. Mr. Brophy described previous conversions of their 40 million line code base as "non-productive" and a "complete waste of our programmer resources".[26] Later that year, the Data Processing Management Association (DPMA) said it was "strongly opposed" to the new standard, citing "prohibitive" conversion costs and enhancements that were "forced on the user".[27][28]

During the first public review period, the committee received 2,200 responses, of which 1,700 were negative form letters.[29] Other responses were detailed analyses of the effect COBOL-80 would have on their systems; conversion costs were predicted to be at least 50 cents per line of code. Fewer than a dozen of the responses were in favor of the proposed standard.[30]

In 1983, the DPMA withdrew its opposition to the standard, citing the responsiveness of the committee to public concerns. In the same year, a National Bureau of Standards study concluded that the proposed standard would present few problems.[28]:41 A year later, a COBOL-80 compiler was released to DEC VAX users, who noted that conversion of COBOL-74 programs posed few problems. The new EVALUATE statement and inline PERFORM were particularly well received and improved productivity, thanks to simplified control flow and debugging.[31]

The second public review drew another 1,000 (mainly negative) responses, while the last drew just 25, by which time many concerns had been addressed.[28]

In late 1985, ANSI published the revised standard. 60 features were changed or deprecated and many[quantify] were added, such as:[10]:150[32]

  • scope terminators (END-IF, END-PERFORM, END-READ, etc.)
  • nested subprograms
  • the CONTINUE statement
  • the EVALUATE statement
  • the INITIALIZE statement
  • inline PERFORM body
  • reference modification
  • I/O status codes

Two amendments followed in 1989 and 1993, the first introducing intrinsic functions and the other providing corrections. The 1985 standard and its amendments were adopted by ISO who subsequently took primary ownership and development of the standard.

COBOL 2002 and object-oriented COBOL[edit]

In the early 1990s it was decided to add object-orientation in the next full revision of COBOL. Object-orientated features were taken from C++ and Smalltalk.[33][34] The initial estimate was to have this revision completed by 1997 and an ISO Committee Draft (CD) was available by 1997. Some vendors (including Micro Focus, Fujitsu, and IBM) introduced object-oriented syntax based on drafts of the full revision. The final approved ISO standard (adopted as an ANSI standard by INCITS) was approved and made available in 2002.

Fujitsu/GTSoftware,[35] Micro Focus and RainCode introduced object-oriented COBOL compilers targeting the .NET Framework.

There were many other new features, many of which had been in the CODASYL COBOL Journal of Development since 1978 and had missed the opportunity to be included in COBOL-85.[36] These other features included:[37](Annex D)[22]:21

Three corringenda were published for the standard: two in 2006 and one in 2009.

There are three technical reports which describe object finalization, XML processing and collection classes for COBOL.[38]

COBOL 2014[edit]

COBOL 2014 includes the following changes:[39](Annex E)

  • Portable arithmetic results have been replaced by IEEE 754 data types
  • Major features have been made optional, such as object-orientation, the VALIDATE facility, the report writer and the screen-handling facility.
  • Method overloading
  • Dynamic capacity tables (a feature dropped from the draft of COBOL 2002)[40]

Legacy[edit]

COBOL programs are used globally in governments and businesses, and are running on diverse operating systems such as z/OS, VME, Unix and Windows. In 1997, the Gartner Group reported that 80% of the world's business ran on COBOL with over 200 billion lines of code and 5 billion lines more being written annually.[41]

Near the end of the twentieth century, the year 2000 problem (Y2K) 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 to fix COBOL code has been attributed[by whom?] to the large amount of business-oriented COBOL, as business applications use dates heavily, and to fixed-length data fields. After the clean-up effort put into these programs for Y2K, a 2003 survey found that many remained in use.[42]:16 The authors said that the survey data suggest "a gradual decline in the importance of Cobol in application development over the [following] 10 years unless ... integration with other languages and technologies can be adopted".[42]:10

In 2006 and 2012, Computerworld surveys found that over 60% of organisations used COBOL (more than C++ and Visual Basic .NET) and that for half of those, COBOL was used for the majority of their internal software.[43][44] 36% of managers said they planned to migrate from COBOL and 25% said they would like to if it was cheaper. Instead, some businesses have migrated their systems from expensive mainframes to cheaper, more modern systems, while maintaining their COBOL programs.[43]

Features[edit]

Syntax[edit]

COBOL has an English-like syntax which is used to describe nearly everything in a program. For example, a condition can be expressed as  x IS GREATER THAN y or more concisely as  x GREATER y  or  x > y. More complex conditions can be "abbreviated" by removing repeated conditions and variables. For example,  a > b AND a > c OR a = d  can be shortened to a > b AND c OR = d. As a consequence of this English-like syntax, COBOL has over 300 keywords.[39](8.9) However, compiler extensions mean many implementations have far more: one implementation recognizes over 1,100 keywords.[45]

A COBOL program is split into four divisions: the identification division, the environment division, the data division and the procedure division. The environment division specifies any program features that depend on the system running it, such as files and character sets. The data division is used to declare variables and parameters. The procedure division contains the program's statements. Each division is sub-divided into sections which are made up of paragraphs. Within these are sentences made up of statements.

Statements are made up of clauses and further statements. Statements containing statements may be terminated in two ways: by a period (implicit termination), which terminates all unterminated statements contained, or by a scope terminator, which terminates the nearest matching open statement.

*> Terminator period ("implicit termination")
IF invalid-record
    IF no-more-records
        NEXT SENTENCE
    ELSE
        READ record-file
            AT END SET no-more-records TO TRUE.
 
*> Scope terminators ("explicit termination")
IF invalid-record
    IF no-more-records
        CONTINUE
    ELSE
        READ record-file
            AT END SET no-more-records TO TRUE
        END-READ
    END-IF
END-IF

Nested statements terminated with a period are a common source of bugs.[46](8.4) For example, examine the following code:

IF x
    DISPLAY y.
    DISPLAY z.

Here, the intent is to display y and z if condition x is true. However, z will be displayed whatever the value of x because the IF statement is terminated by an erroneous period after  DISPLAY y.

Another bug is a result of the dangling else problem, when two IF statements can associate with an ELSE.

IF x
    IF y
        DISPLAY a
ELSE
    DISPLAY b.

In the above fragment, the ELSE associates with the  IF y  statement instead of the  IF x  statement, causing a bug. Prior to the introduction of explicit scope terminators, preventing it would require  ELSE NEXT SENTENCE  to be placed after the inner IF.[46](8.4)

Code format[edit]

Fixed format code is the default code format. Up to COBOL-85, fixed-format code was split into 5 areas:

Name Column(s) Usage
Sequence number area 1–6 Originally used for card/line numbers, this area was ignored by the compiler.
Indicator area 7 The following characters could go here:
  • * – a comment line
  • / – a comment line which would be printed on a new page of a source listing
  • - – a continuation line where words from the previous line could be continued
  • D – a line used for debugging, which would otherwise be ignored
Area A 8–11 The following had to begin here: DIVISION, SECTION and procedure headers, 01 and 77 level numbers and FD and SD record descriptors.
Area B 12–72 Any other code not allowed in Area A.
Program name area 73– Historically up to column 80 for punched cards, it was used to identify the program the card belonged to.

In COBOL 2002, free-format code was introduced. It allowed code to be placed in any column of the file, like newer languages such as C and Pascal. The * comment indicator was replaced by *> which could be placed anywhere and be used in fixed-format source code.The / indicator was replaced with a new compiler directive and words cannot be continued. Fixed-format code remains the default format, however, and the only changes to it in COBOL 2002 were that Areas A and B were merged and their size left to the implementer.[37](D.2)

Aggregated Data[edit]

Data items in COBOL are declared hierarchically through the use of level-numbers which indicate if a data item is part of another. An item with a higher level-number is subordinate to an item with a lower one. Data items which are not subordinate to another item are called records. Items that have no subordinate data items are called elementary items; those that do are called group items.[47](App. A)

       01  some-record.
           03  num            PIC 9(10).
           03  the-date.
               05  the-year   PIC 9(4).
               05  the-month  PIC 99.
               05  the-day    PIC 99.

In the above example, num and the-date are subordinate to the record some-record while the-year, the-month and the-day are part of the group item the-date.

Level-numbers used to describe standard data items are between 1 and 49. A level-number of 66 is used to declare a re-grouping of previously defined items, irrespective of how those items are structured.[46](19.9) 77 indicates the item is stand-alone and in such situations, is equivalent to the level-number 1. 88 declares condition names (so-called 88-levels) which are true when the parent data item contains one of the values specified in the condition.[47](5.8.5)

Data types[edit]

Standard COBOL provides the following data types:[39]:118

Data type Sample declaration Notes
Alphabetic PIC A(30) May only contain letters or spaces
Alphanumeric PIC X(30) May contain any characters
Boolean PIC 1 USAGE BIT Data stored in the form of 0s and 1s, as a binary number
Index USAGE INDEX Used to reference table elements
National PIC N(30) Similar to alphanumeric, but using an extended character set, e.g. UTF-8
Numeric PIC 9(5)V9(5) May contain only numbers
Object USAGE OBJECT REFERENCE May reference either an object or be NULL
Pointer USAGE POINTER

Numeric[edit]

Numeric data can be stored in several formats:[39](13.18.59.3)

  • Binary, where a minimum size is either specified by the PICTURE clause or by a USAGE clause such as BINARY-LONG.
  • USAGE COMPUTATIONAL, where data may be stored in whatever format the implementation provides; often equivalent to  USAGE BINARY
  • USAGE DISPLAY, the default format, where data is stored as a string
  • Floating-point, in either an implementation-dependent format or according to IEEE 754.
  • USAGE NATIONAL, where data is stored as a string using an extended character set
  • USAGE PACKED-DECIMAL, where data is stored in the smallest possible decimal format (typically packed binary-coded decimal)

Edited[edit]

Edited data are formatted string types that are specified by a PICTURE clause. For example, a 9 indicates that there will be a numeric character at a position and a , indicates that there will be a comma character at that position unless the character after it is a space, in which case it will also be a space.[47](5.9.33) There are 3 types of edited data: alphanumeric-edited, national-edited and numeric-edited. Numeric-edited data can be represented using either the normal character set or the NATIONAL set.

Extensions[edit]

Most vendors provide additional types, equivalents of which are now in the standard. These extensions include:[47](5.9.48)[48]

Data type Sample declaration Notes
Single-precision floating-point USAGE COMPUTATIONAL-1 Equivalent to USAGE FLOAT-SHORT.
Double-precision floating-point USAGE COMPUTATIONAL-2 Equivalent to USAGE FLOAT-LONG.
Signed packed decimal PIC S9V999 USAGE COMPUTATIONAL-3 Equivalent to USAGE PACKED-DECIMAL.
Fixed-point binary PIC S999V99 USAGE COMPUTATIONAL-4 Equivalent to USAGE BINARY.
Fixed-point native binary PIC S9(5) USAGE COMPUTATIONAL-5 May be signed or unsigned. The PICTURE clause does not directly state the size of the variable which can either have 16, 32 or 64 bits. For example, the example specifies that it will have a maximum value of 2147483647 instead of 99999.
Unsigned packed decimal PIC 99V999 USAGE COMPUTATIONAL-6
Double-byte characters PIC G(20) Equivalent to alphanumeric data, but using a double-byte character set.

Files[edit]

COBOL supports three file formats, or organizations: sequential, indexed and relative. In sequential files, records are contiguous and must be traversed sequentially, similarly to a linked list. Indexed files have one or more indexes which allow records to be randomly accessed and which can be sorted on them. Each record must have a unique key, but alternate record keys need not be unique. Implementations of indexed files vary between vendors, although common implementations, such as C-ISAM and VSAM, are based on IBM's ISAM. Relative files, like indexed files, have a unique record key, but they do not have alternate keys. A relative record's key is its ordinal position; for example, the 10th record has a key of 10. This means that creating a record with a key of 5 may require the creation of (empty) preceding records. Relative files also allow for both sequential and random access.[39](D.2.1)

A common non-standard extension is the line sequential organization, used to process text files. Records in a file are terminated by a newline and may be of varying length.[49]

Procedures[edit]

The sections and paragraphs in the procedure division can be used as labels and simple subroutines. Unlike in other divisions, paragraphs do not need to be in sections. Execution goes down through the procedures of a program until it is terminated. Procedures can be used with the PERFORM statement which acts like a GOSUB in BASIC. Performing a section means that execution travels through any paragraphs it contains, even if doing so will take control flow out of the specified procedures.

In COBOL-74, subprograms were added, allowing the separation and encapsulation of different parts of the program. Subprograms can be called either statically or dynamically. Static calls are known at compile time, but dynamic calls are evaluated at runtime based on a string or pointer variable.

Intrinsic functions were added to COBOL in the 1989 addendum to COBOL-85. The addendum added various common mathematical, string and date functions including SIN, UPPER-CASE and CURRENT-DATE.[50] Functions may be preceded by the word FUNCTION and those with no parameters may be used with or without parentheses.[39](8.4.2.2) In 2002, user-defined functions were added.

Self-modifying code[edit]

The original COBOL specification supported the infamous  ALTER X TO PROCEED TO Y  statement, for which many compilers generated self-modifying code. X and Y are paragraph labels, and any  GO TO X  statements executed after such an ALTER statement mean  GO TO Y  instead. Many compilers still support it,[51] but it was deemed obsolete in the COBOL 1985 standard[52] and should not be used in new programs. The use of ALTER has been banned altogether for some time by many software companies as part of their programming practices.

Object-oriented programming[edit]

Classes and interfaces were added in COBOL 2002. Classes have factory objects, containing class methods and variables, and instance objects, containing instance methods and variables.[39](D.18.2) Inheritance and interfaces provide polymorphism. Support for generic programming is provided through parameterized classes, which can be instantiated to use any class or interface. Objects are stored as references which may be restricted to a certain type. There are two ways of called a method: the INVOKE statement, which acts similarly to CALL, or through inline method invocation, which is analogous to using functions.[39](D.18)

*> These are equivalent.
INVOKE my-class "foo" RETURNING bar
MOVE my-class::"foo" TO bar *> Inline method invocation

COBOL does not provide a way to hide methods. Class data can be hidden, however, by declaring it without a PROPERTY clause, which leaves the user with no way to access it.[39]:100 Method overloading was added in COBOL 2014.[39]:873

Hello, world[edit]

A "Hello, world" program in COBOL:

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

Criticism and defense[edit]

Lack of structure[edit]

In his letter to an editor in 1975 entitled "How do we tell truths that might hurt?" which was critical of several of COBOL's contemporaries, 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."[53]

In his dissenting response to Dijkstra's article and the above "offensive statement," computer scientist Howard E. Tompkins defended structured COBOL: "COBOL programs with convoluted control flow indeed tend to 'cripple the mind'," but this was because "There are too many such business application programs written by programmers that have never had the benefit of structured COBOL taught well..."[54]

COBOL lacked any facility for defining independent subprograms until COBOL-74. This complicated development because it meant that all variables were global and could be modified anywhere within the program. However, its varied control structures reduced the need for GO TOs; the PERFORM statement, for example, allowed programmers to easily access powerful looping facilities.[55]:349–350

Additionally, the introduction of OO-COBOL has added support for object-oriented programming as well as user-defined functions and user-defined data types to COBOL's repertoire.

Compatibility issues after standardization[edit]

COBOL-85 was not fully compatible with earlier versions, resulting in the "caesarean birth" of COBOL-85.[clarification needed] Joseph T. Brophy, the CIO of Travelers Insurance, spearheaded an effort to inform users of COBOL of the heavy reprogramming costs of implementing the new standard.[10]:11 As a result, the ANSI COBOL Committee received more than 2,200 letters from the public, mostly negative, requiring the committee to make changes. On the other hand, conversion to COBOL-85 was thought to increase productivity in future years, thus justifying the conversion costs.[10]

Verbose syntax[edit]

COBOL syntax has often been criticized for its verbosity. However, proponents note that this was intentional in the language design because it made the code self-documenting, easing program maintenance.[19]:53 COBOL was intended to be easier for programmers to learn and use,[9](II.1.1) but while being readable to non-technical staff such as managers.[8]:ID/10[55]:350 The desire for readability and good program documentation is why COBOL has English-like syntax and structural elements, such as nouns, verbs, clauses, sentences, sections, and divisions. Consequently, COBOL is considered by one source to be "The most readable, understandable and self-documenting programming language in use today. [...] Not only does this readability generally assist the maintenance process but the older a program gets the more valuable this readability becomes."[56] On the other hand, by 1984, maintainers of COBOL programs were struggling to deal with "incomprehensible" code[8]:ID/10 and the main changes in COBOL-85 were there to help ease maintenance.[29]:48

Jean Sammet, a short-range committee member, noted that "little attempt was made to cater to the professional programmer, in fact people whose main interest in programming tend to be very unhappy with COBOL" which she attributed to COBOL's verbose syntax.[8]:ID/14

Alienation from the computer science community[edit]

The COBOL community has always been isolated from the computer science community. No academic computer scientists participated in the design of COBOL; all of those on the committee from commerce or government. This was due to the differing interests of computer scientists at the time, who were more interested in fields like numerical analysis, physics and system programming than the commercial file-processing problems which COBOL development tackled. The COBOL specification did not use the new Backus-Naur form to describe the language's syntax, resulting in severe criticism at the time.[55]:348–349

Later, COBOL suffered from a shortage of material covering it; it took until 1963 for introductory books to appear. By 1985, there were twice as many books on Fortran and four times as many on BASIC than on COBOL in the Library of Congress.[55]:349 As COBOL became a mainstream language, COBOL suffered as university professors taught more modern, state-of-the-art languages and techniques instead of COBOL which was said to have a "trade school" nature.[55]:351 Donald Nelson, the chair of the CODASYL COBOL committee said in 1984 that "academics ... hate COBOL" and that computer science graduates "had 'hate COBOL' drilled into them".[57]

Flawed language features[edit]

COBOL suffered from poor string-handling facilities, which were only fixed in COBOL-74. The hard to spot and easily mislaid scope-delimiting period was superseded in COBOL-85 by scope-terminators, 25 years after the beginend delimiters were introduced in ALGOL.[58] Until COBOL-85, only paragraphs could be used in PERFORM statements, which made programs harder to understand as the reader had to search for the body of the statement.[55]:350 Functions were introduced in the 1989 Amendments and user-defined functions were only introduced in COBOL 2002.[37](D.1)

Design by committee[edit]

There were doubts about the effectiveness of the design process (sometimes from those taking part in it). Short-term committee member Howard Bromberg said that there was "little control" over the development process and that it was "plagued by discontinuity of personnel and ... a lack of talent".[5]:301

COBOL standards have repeatedly suffered from delays: COBOL-85 arrived five years later than hoped,[59] COBOL 2002 was five years late,[33] and COBOL 2014 was six years late.[60] To combat delays, the standard committee allowed the creation of optional addenda which would add features more quickly than by waiting for the next standard revision. However, some committee members raised concerns about incompatibilities between implementations and frequent modifications of the standard.[61]

Other defenses[edit]

COBOL's data structures influenced subsequent programming languages. Its record and file structure influenced PL/I and Pascal, and the REDEFINES clause was a predecessor to Pascal's variant records. Explicit file structure definitions preceded the development of database management systems and aggregated data was a significant advance over Fortran's arrays.[55]:349

COBOL included "primitive capabilities for a library system" in 1959 through the INCLUDE statement (later COPY),[13]:274[9](2.2.5) the same year that JOVIAL introduced the "Communication Pool" concept, which allowed programs to share data by providing a centralised data description.[13]:369 Despite Jean Sammet describing these capabilities as "inadequate" in retrospect,[13]:258 the COPY facility became a successful feature that influenced the development of include directives.[55]

Until COBOL 2002, COBOL was a simple language with a limited scope of function (with no pointers, no user-defined types, and no user-defined functions), encouraging a straightforward coding style. This has made it well-suited to its primary domain of business computing—where the program complexity lies in the business rules that need to be encoded rather than sophisticated algorithms or data structures.

Standardization meant programs written in COBOL are portable and language has since spread on to a wide variety of hardware platforms and operating systems.[62] Additionally, the rigid hierarchical structure restricts the definition of external references to the Environment Division, which simplifies platform changes in particular.[56]

See also[edit]

References[edit]

  1. ^ Porter Adams, Vicki (5 October 1981). "Captain Grace M. Hopper: the Mother of COBOL". InfoWorld 3 (20): 33. ISSN 0199-6649. 
  2. ^ Betts, Mitch (6 Jan 1992). "Grace Hopper, mother of Cobol, dies". Computerworld 26 (1): 14. ISSN 0010-4841. 
  3. ^ Robinson, Brian (9 July 2009). "Cobol remains old standby at agencies despite showing its age". FCW. Public Sector Media Group. Retrieved 26 April 2014. 
  4. ^ "ISO/IEC 1989:2014". ISO. 26 May 2014. Retrieved 7 June 2014. 
  5. ^ a b c d e f g h i j k l m n o p Beyer, Kurt (2009). Grace Hopper and the Invention of the Information Age. MIT Press. ISBN 978-0262013109. LCCN 2008044229. 
  6. ^ "Early Meetings of the Conference on Data Systems Languages". IEEE Annals of the History of Computing 7 (4): 316. 1985. doi:10.1109/MAHC.1985.10047.  edit
  7. ^ a b c d e f Sammet, Jean E. (23 July 2004). "COBOL". In Riley, Edwin D. Concise Encyclopedia of Computer Science. Wiley. ISBN 978-0470090954. OCLC 249810423. 
  8. ^ a b c d e Conner, Richard L. (14 May 1984). "Cobol, your age is showing". Computerworld 18 (20): ID/7–ID/18. ISSN 0010-4841. 
  9. ^ a b c d e f g h CODASYL (July 1969). CODASYL COBOL Journal of Development 1968. National Bureau of Standards. LCCN 73601243. 
  10. ^ a b c d Garfunkel, Jerome (1987). The COBOL 85 Example Book. New York: Wiley-Interscience. ISBN 0-471-80461-4. 
  11. ^ a b "The Story of the COBOL Tombstone" (PDF). The Computer Museum Report (The Computer Museum) 13: 8–9. Summer 1985. Archived from the original on 3 April 2014. Retrieved 29 June 2014. 
  12. ^ "COBOL Tombstone". Computer History Museum. Retrieved 29 June 2014. 
  13. ^ a b c d Wexelblat, Richard (1981). History of Programming Languages. Boston: Academic Press. ISBN 0-12-745040-8. 
  14. ^ Sammet, Jean (1978). "The Early History of COBOL". ACM SIGPLAN Notices (Association for Computing Machinery, Inc.) 13 (8): 121–161. doi:10.1145/960118.808378. Retrieved 14 January 2010. 
  15. ^ Bemer, Robert William. "A View of the History of COBOL" (PDF). Honeywell Computer Journal (Honeywell): 130–135. Retrieved 28 June 2014. 
  16. ^ "Oral History of Captain Grace Hopper" (PDF). Computer History Museum. December 1980. Retrieved 28 June 2014. 
  17. ^ Sullivan, Patricia (25 June 2004). "Computer Pioneer Bob Bemer, 84". The Washington Post. pp. B06. Retrieved 28 June 2014. 
  18. ^ Bemer, Bob. "Thoughts on the Past and Future". Archived from the original on 16 May 2014. Retrieved 28 June 2014. 
  19. ^ a b c d e f Belzer, Jack; Holzman, Albert G.; Kent, Allen (1 December 1976). "COBOL". Encyclopedia of Computer Science and Technology: Volume 5. CRC Press. ISBN 978-0824722555. 
  20. ^ Williams, Kathleen Broome (10 November 2012). Grace Hopper: Admiral of the Cyber Sea. US Naval Institute Press. ISBN 978-1612512655. OCLC 818867202. 
  21. ^ Triance, J. M. (1974). Programming in COBOL: A Course of Twelve Television Lectures. Manchester University Press. p. 87. ISBN 0-7190-0592-2. 
  22. ^ a b Klein, William M. (4 October 2010). "The History of COBOL" (PDF). Archived from the original on 7 January 2013. Retrieved 7 January 2014. 
  23. ^ Baird, George N.; Oliver, Paul (May 1977). "1974 Standard (X3.23–1974)". Programming Language Standards — Who Needs Them?. pp. 19–21. Archived from the original on 7 January 2014. Retrieved 7 January 2014. 
  24. ^ Culleton, John R., Jr. (23 July 1975). "'Spotty' Availability A Problem...". Computerworld 9 (30): 17. ISSN 0010-4841. 
  25. ^ Simmons, Williams B. (18 June 1975). "Does Cobol's Report Writer Really Miss the Mark?". Computerworld 9 (25): 20. ISSN 0010-4841. 
  26. ^ Shoor, Rita (26 January 1981). "User Threatens Suit Over Ansi Cobol-80". Computerworld 15 (4): 1, 8. ISSN 0010-4841. 
  27. ^ Shoor, Rita (26 October 1981). "DPMA Takes Stand Against Cobol Draft". Computerworld 15 (43): 1–2. ISSN 0010-4841. 
  28. ^ a b c Gallant, John (16 September 1985). "Revised Cobol standard may be ready in late '85". Computerworld 19 (37): 1, 8. ISSN 0010-4841. 
  29. ^ a b "Expert addresses Cobol 85 standard". Computerworld 19 (37): 41, 48. 16 September 1985. ISSN 0010-4841. 
  30. ^ Paul, Lois (15 March 1982). "Responses to Cobol-80 Overwhelmingly Negative". Computerworld 16 (11): 1, 5. ISSN 0010-4841. 
  31. ^ Gillin, Paul (19 November 1984). "DEC users get head start implementing Cobol-80". Computerworld 18 (47): 1, 6. ISSN 0010-4841. 
  32. ^ Roy, M K; Dastidar, D Ghost (1 June 1989). "Features of COBOL - 85". COBOL Programming: Problems and Solutions (2nd ed.). McGraw-Hill Education. pp. 438–451. ISBN 978-0074603185. 
  33. ^ a b Saade, Henry; Wallace, Ann (October 1995). "COBOL '97: A Status Report". Dr. Dobb's Journal. Retrieved 21 April 2014. 
  34. ^ Arranga, Edmund C.; Coyle, Frank P. (February 1998). Object-Oriented COBOL. Cambridge University Press. p. 15. ISBN 978-0132611404. "Object-Oriented COBOL's style reflects the influence of Smalltalk and C++" 
  35. ^ "NetCOBOL for .Net". netcobol.com. GTSoftware. 2013. Retrieved 29 January 2014. 
  36. ^ "A list of Codasyl Cobol features". Computerworld 18 (37). 10 September 1984. p. ID/28. ISSN 0010-4841. Retrieved 8 June 2014. 
  37. ^ a b c "Proposed Revision of ISO 1989:1985" (ZIP). ISO. 22 February 1998. Archived from the original on 12 December 2000. Retrieved 12 July 2014. 
  38. ^ "JTC1/SC22/WG4 - COBOL". ISO. 30 June 2010. Retrieved 27 April 2014. 
  39. ^ a b c d e f g h i j "ISO/IEC 1989:20xx FCD 1.0 - Programming language COBOL" (PDF). ISO. 13 July 2010. Retrieved 9 February 2014. 
  40. ^ Schricker, Don (2 December 1998). "J4: COBOL Standardization". Micro Focus. Archived from the original on 24 February 1999. Retrieved 12 July 2014. 
  41. ^ Kizior, Ronald J.; Carr, Donald; Halpern, Paul. "Does COBOL Have a Future?". The Proceedings of the Information Systems Education Conference 2000 17 (126). Retrieved 2012-09-30. 
  42. ^ a b Carr, Donald; Kizior, Ronald J. (13 June 2003). "Continued Relevance of COBOL in Business and Academia: Current Situation and Comparison to the Year 2000 Study" (PDF). Retrieved 5 January 2014. 
  43. ^ a b Mitchell, Robert L. (4 October 2006). "Cobol: Not Dead Yet". Computerworld. Retrieved 27 April 2014. 
  44. ^ "Cobol brain drain: Survey results". Computerworld. 14 March 2012. Retrieved 27 April 2014. 
  45. ^ "Reserved Words Table". Micro Focus Visual COBOL 2.2 COBOL Language Reference. Micro Focus. Retrieved 3 March 2014. 
  46. ^ a b c McCracken, Daniel D.; Golden, Donald G. (1988). A Simplified Guide to Structured COBOL Programming (2nd ed.). Wiley. ISBN 0-471-61054-2. LCCN 87034608. 
  47. ^ a b c d Cutler, Gary (9 April 2014). "GNU COBOL Programmer's Guide" (3rd ed.). Retrieved 25 February 2014. 
  48. ^ "DATA DIVISION—Data description entry". Enterprise COBOL for z/OS Language Reference. IBM. 2013. Retrieved 25 February 2014. 
  49. ^ "File Organizations". File Handling. Micro Focus. 1998. Retrieved 27 June 2014. 
  50. ^ Parkin, Andrew; Yorke, Richard (1 December 1995). "Intrinsic Functions". Cobol for Students. Elsevier. ISBN 0-340-64552-0. 
  51. ^ Examples of compiler support for ALTER can be seen in the following:
    • Tiffin, Brian. September 2013. "State of the Project". GNU Cobol. Retrieved 5 January 2014. 
    • "The ALTER Statement". Micro Focus Visual COBOL 2.2 for Visual Studio 2013 COBOL Language Reference. Micro Focus. Retrieved 5 January 2014. 
    • "ALTER Statement (Nucleus)" (PDF). COBOL85 Reference Manual. Fujitsu. November 1996. p. 555. Retrieved 5 January 2014. 
    • "ALTER Statement". Enterprise COBOL for z/OS Language Reference. IBM. June 2013. Retrieved 5 January 2014. 
  52. ^ "The ALTER Statement". Micro Focus Visual COBOL 2.2 for Visual Studio 2013 COBOL Language Reference. Micro Focus. Retrieved 28 December 2013. "The ALTER statement is classed as an obsolete element in the ANSI'85 standard and is scheduled to be deleted from the next full revision of the ANSI Standard." 
  53. ^ Dijkstra, Edsger W. (2006). "E. W. Dijkstra Archive: How do we tell truths that might hurt? (EWD498)". University of Texas at Austin. Retrieved August 29, 2007. 
  54. ^ Tompkins, H. E. (1983). "In defense of teaching structured COBOL as computer science". ACM SIGPLAN Notices 18 (4): 86. doi:10.1145/948176.948186.  edit
  55. ^ a b c d e f g h Shneiderman, B. (October 1985). "The Relationship Between COBOL and Computer Science". Annals of the History of Computing (IEEE) 7 (4): 348–352. doi:10.1109/MAHC.1985.10041. 
  56. ^ a b Coughlan, Michael (2002). "Introduction to COBOL". Retrieved 3 February 2014. 
  57. ^ "An interview: Cobol defender". Computerworld 18 (37). 10 September 1984. pp. ID/29–ID/32. ISSN 0010-4841. Retrieved 8 June 2014. 
  58. ^ O'Regan, Gerard (6 March 2012). A Brief History of Computing (2nd ed.). Springer. p. 128. doi:10.1007/978-1-4471-2359-0. ISBN 978-1-4471-2358-3. LCCN 2012934180. 
  59. ^ "(Unknown)". Proceedings of Share (Share Inc.) 52 (2): 1975. 1979. "The earliest date that a new COBOL standard could be developed and approved is the year 1980, so the revision of X3.23-1974 is referenced as COBOL 80" 
  60. ^ "Resolutions from WG4 meeting 24 - June 26-28, 2003 Las Vegas, Nevada, USA" (doc). 11 July 2003. p. 1. Retrieved 29 June 2014. "a June 2008 revision of the COBOL standard" 
  61. ^ Babcock, Charles (14 July 1986). "Cobol standard add-ons flayed". Computerworld 20 (28): 1, 12. 
  62. ^ This can be seen in:
    • "Visual COBOL". IBM PartnerWorld. IBM. 21 August 2013. Archived from the original on 12 July 2014. Retrieved 5 February 2014. "Micro Focus Visual COBOL delivers the next generation of COBOL development and deployment for Linux x86-64, Linux for System z, AIX, HP/UX, Solaris, and Windows." 
    • "COBOL Compilers family". ibm.com. IBM. Archived from the original on 23 February 2014. Retrieved 5 February 2014. 
    • Tiffin, Brian (4 January 2014). "What platforms are supported by GNU Cobol?". GNU Cobol FAQ. Archived from the original on 14 December 2013. Retrieved 5 February 2014. 

External links[edit]