Encyclopedia of Computer Science and Technology

COBOL 91professional programmers. (This theme of “programmingwithout programmers” would recur with regard to otherlanguages such as RPG, BASIC, and various database systems,always with limited success.)Program StructureA COBOL program as a whole resembles a business form inthat it is divided into specific sections called divisions, eachwith required and optional items.The Identification division simply identifies the programmerand gives some information about the program:IDENTIFICATION DIVISION.PROGRAM-ID WEEKLY REPORT.AUTHOR JAMES BRADLEY.DATE-WRITTEN DECEMBER 10, 2000.DATE-COMPILED DECEMBER 12, 2000.REMARKS THIS IS AN EXAMPLE PROGRAM.The Environment division contains specifications aboutthe environment (hardware) for which the program willbe compiled. In some cases (for example, microcomputerversions of COBOL) it may not be needed. In other cases, itmight simply have a Configuration section that specifies themachine to be used:ENVIRONMENT DIVISION.CONFIGURATION SECTION.SOURCE-COMPUTER IBM-370.OBJECT-COMPUTER IBM-370.(The reason for the separate source and object computers isthat programs were sometimes compiled on one computerfor use on another, often smaller, one.)In some cases, the Environment Division must alsoinclude an Input-Output section that specifies devices andfiles that will be used by the program. For example:INPUT-OUTPUT SECTION.FILE-CONTROL.SELECT STUDENT-FILE ASSIGN TO READERSELECT STUDENT-LISTING ASSIGN TO LOCAL-PRINTERThe Data division gives a description of the data recordsand other items that will be processed by the program.It is roughly comparable to the declarations of variablesin languages such as Pascal, C, or BASIC. Since COBOLfocuses on the processing of file records and the formattingof reports, it tends to have fewer data types than manyother languages, but it makes it easier to describe the kindsof data structures commonly used in business applications.For example, it is easy to describe records that have fieldsand subfields by using level numbers to indicate the relationship:DATA DIVISION.FILE SECTION.FD INFILELABEL RECORDS ARE OMITTED.01 STUDENT-DATA.02 STUDENT-ID PIC 999999.02 STUDENT-NAME.03 LAST-NAME PIC X(15).03 INITIAL PIC X.03 FIRST-NAME PIC X(10).02 GPA PIC 9.99The “PIC” or picture clause specifies the type of data(using 9’s and a decimal point for numbers and X for text)and the length. In addition to specifying the input records,the Data division often includes items that specify the formatof the lines of output that are to be printed.The Procedure division provides the statements thatperform the actual data manipulation. Procedures can beorganized as subroutines (roughly equivalent to proceduresor functions on other languages). Some sample procedurestatements are:READ STUDENT-DATA INTO STUDENT-WORK-RECORDAT END MOVE ‘E’ TO PROC-FLAG-STGO TO EXIT-PRINTADD 1 TO TOTAL-STUDENT-RECORDSMathematical expressions can be computed using aCompute statement:COMPUTE GPA = TOTAL-GRADES / CLASSESBranching (if) statements are available, and looping isprovided by the Perform statement, for example:PERFORM 100-PRINT-LINEUNTIL LINES-FL IS EQUAL TO ‘E’(As with older versions of BASIC, subroutines are numbered.)Impact and ProspectsFrom the 1960s through the 1980s, COBOL became theworkhorse language for business applications for mainframeand mid-size computers, and it is still widely usedtoday. (The concerns about possible problems at the endof the century often involved older programs written inCOBOL, see y2k problem.) The main line of programminglanguage evolution bypassed COBOL and went throughAlgol (a contemporary of COBOL) and on into Pascal, C,and other block-structured languages (see also structuredprogramming).Some modern versions of COBOL have incorporatedlater developments in structured programming (such asmodularization) and even object-oriented design. COBOLhas also shown considerable versatility in accommodatingmodern development frameworks, including Microsoft.NETas well as processing now-ubiquitous XML data. Nevertheless,usage of COBOL continues to decline slowly as developersincreasingly turn to languages such as C++, scriptinglanguages, or database development systems.Further ReadingBivar de Oliveria, Rui. The Power of COBOL: For Systems Developersof the 21st Century. Charleston, S.C.: BookSurge, 2006.COBOL Portal. Available online. URL: http://www.cobolportal.com. Accessed June 8, 2007.