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16-1 COBOL for the 21 st Century Nancy Stern Hofstra University Robert A. Stern Nassau Community College James P. Ley University of Wisconsin-Stout (Emeritus)

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Presentation on theme: "16-1 COBOL for the 21 st Century Nancy Stern Hofstra University Robert A. Stern Nassau Community College James P. Ley University of Wisconsin-Stout (Emeritus)"— Presentation transcript:

1 16-1 COBOL for the 21 st Century Nancy Stern Hofstra University Robert A. Stern Nassau Community College James P. Ley University of Wisconsin-Stout (Emeritus) John Wiley & Sons, Inc. 11th edition

2 16-2 Improving Program Productivity Using The COPY, CALL, and Other Statements Chapter 16

3 16-3 Chapter Objectives To familiarize you with COPY statement for copying parts of a program stored in a library CALL statement for executing called programs as subroutines Text manipulation with STRING and UNSTRING statements

4 16-4 Chapter Contents COPY Statement CALL Statement STRING and UNSTRING Statements

5 16-5 COPY Statement To copy prewritten COBOL entries stored in a library into a program Often used to copy –FD, 01 entries that define and describe files and records –Tables –SCREEN SECTIONs –Standard modules used in PROCEDURE DIVISION

6 16-6 Benefits of COPYing Entries Saves programmer coding, debugging time by using code already written Promotes program standardization - all entries copied from library are identical Reduces time needed to modify code - changes made once to library copy Library entries can be well-documented so meaningful to all users

7 16-7 COPY Statement COPY test-name OF library-name. IN Library-name is external-name, 1 to 8 characters, letters and digits only Use in ENVIRONMENT, DATA, or PROCEDURE DIVISION Format

8 16-8 COPY Statement Example Suppose file called Customer, stored in library contains following entries: 01Customer-Rec. 05Cust-NoPic X(5). 05Cust-NamePic X(20). 05Cust-AddressPic X(30). 05Cust-Bal-DuePic 9(4)V99.

9 16-9 COPY Statement Example Code COPY statement at point in program where entries should appear Data Division. File Section. FDCustFile. Copy Customer. In source listing, copied lines are marked with a C or other designator

10 16-10 Source Listing with COPY …... 11FDCustFile. 12Copy Customer. 13C01Customer-Rec. 14C05Cust-NoPic X(5). 15C05Cust-NamePic X(20). 16C05Cust-AddressPic X(30). 17C05Cust-Bal-DuePic 9(4)V99. Line numbers followed by C are copied statements

11 16-11 Changing COPYed Entries REPLACING ==pseudo-text-1== ==pseudo-text-2== identifier-1BY identifier-2... literal-1 literal-2 word-1 word-2 Add REPLACING clause to COPY to make changes to copied entries Format

12 16-12 Changing COPYed Entries Copy Customer Replacing Cust-No By Cust-Number, ==X(5)== By ==X(6)==. Changes copied line 14C –From: 14C05Cust-No Pic X(5). –To:14C05Cust-Number Pic X(6). Example

13 16-13 CALL Statement Used in PROCEDURE DIVISION to CALL or reference independent subprograms stored in library Calling program - main program that calls or references subprogram Called program - subprogram stored in separate file that is linked and executed within main program

14 16-14 Called Program (Subprogram) Compiled, debugged, stored in library to be called when needed Typical subprograms include: –Edit routines –Error control checks –Standard calculations –Summary, total printing

15 16-15 Advantages of Subprograms Avoids duplication of effort Improves programmer productivity Provides greater flexibility Changes to called program can be made without modifying calling program Results in greater standardization

16 16-16 CALL vs COPY COPY brings entries into program as is CALL causes an entire program (the called program) to be executed –Data passed from calling to called program –Entire called program (subprogram) executed –Data passed back from called program –Control returns to calling program

17 16-17 CALL vs COPY Typically, COPY ENVIROMENT, DATA DIVISION entries into source program CALL subprograms in PROCEDURE DIVISION rather than COPY them

18 16-18 CALL Statement CALL literal-1 [USING identifier-1 …] To call subprogram into main program literal-1 is PROGRAM-ID name in called program Enclose in quotes Format

19 16-19 Calling and Called Programs Identification Division.... Procedure Division.... Call 'Sub1'... Call 'Sub2'... Identification Division. Program-ID. Sub1. … Procedure Division. Exit Program. Identification Division. Program-ID. Sub2. … Procedure Division. Exit Program. 1 2 3 4

20 16-20 Calling and Called Programs 1.Subprogram Sub1 called and executed in its entirety 2.Control returns to calling program 3.Subprogram Sub2 called and executed in its entirety 4.Control returns to calling program

21 16-21 CALL … USING USING clause required if data passed between calling and called program Fields passed are called parameters Parameter passed in several ways: –Value of parameter may be passed to and used by subprogram but not changed –Value for parameter may be calculated by instructions in subprogram and passed back to main program

22 16-22 CALL … USING Example Suppose a main program –Reads in employee records –Produces report showing employee salary, Social Security tax and Medicaid tax (taxes referred to as FICA taxes) Subprogram is to calculate amount of each tax based on the salary field –Assume PROGRAM-ID is FICAProg

23 16-23 CALL … USING Example Parameters needed –Salary (WS-Ann-Sal) Passed to subprogram, used to calculate taxes but not changed by subprogram –Tax fields Soc-Sec and Med-Tax Subprogram calculates values for these parameters and passes them back to main program

24 16-24 Calling Program Requirements CALL statement with: –Literal same as PROGRAM-ID of called program –List of parameters in USING clause Call 'FICAProg' Using WS-Ann-Sal, Soc-Sec, Med-Tax Example

25 16-25 Called Program Requirements PROGRAM-ID identifier is literal used in CALL in main program LINKAGE SECTION must be defined in DATA DIVISION –Follows FILE and WORKING-STORAGE SECTIONs –Describes all items passed between main and subprogram –Format same as WORKING-STORAGE

26 16-26 Called Program Requirements PROCEDURE DIVISION header must include USING clause –Lists all parameters or fields defined in LINKAGE SECTION EXIT PROGRAM –Last executed statement in called program –Returns control back to calling program

27 16-27 Subprogram Example Identification Division. Program-ID. FICAProg. Data Division. Linkage Section. 01WS-Ann-SalPic 9(6). 01Soc-SecPic 9(4)V99. 01Med-TaxPic 9(5)V99.

28 16-28 Subprogram - Procedure Division Procedure Division Using WS-Ann-Sal, Soc-Sec, Med-Tax. If WS-Ann-Sal <= 84900 Compute Soc-Sec =.062 * WS-Ann-Sal Else Compute Soc-Sec =.062 * 84900 End-If Compute Med-Tax =.0145 * WS-Ann-Sal Exit Program.

29 16-29 Subprogram Example When FICAProg is called –Value of WS-Ann-Sal passed to subprogram –Value of Soc-Sec and Med-Tax undefined When FICAProg finished –Values calculated for Soc-Sec and Med- Tax passed back to main program

30 16-30 Parameter Correspondence Parameters passed in sequence –First parameter in CALL … USING passed to first parameter in PROCEDURE DIVISION USING clause and so on Number of parameters in both USING clause should be the same PIC clauses for corresponding parameters must be same

31 16-31 Parameter Correspondence Data-names of corresponding parameters may be same or different Parameters paired by sequence, not by data-name List parameters in same order in both USING clauses

32 16-32 Parameter Correspondence Assume USING clauses are: Call 'FICAProg' Using Soc-Sec, Med-Tax, WS-Ann-Sal Procedure Division Using WS-Ann-Sal, Soc-Sec, Med-Tax. –Soc-Sec passed as value for WS-Ann-Sal –Calculations in subprogram will be incorrect, values passed back incorrect

33 16-33 STRING Statement To combine or concatenate several fields into one Consider following entries: 05Name. 10Last-NamePic X(10). 10First-NamePic X(10). 10Middle-NamePic X(6).

34 16-34 STRING Statement Suppose name fields have values below Print name with single blank between parts: THOMAS ALVA EDISON

35 16-35 STRING Statement Format STRINGidentifier-1... literal-1 identifier-2 DELIMITED BYliteral-2... SIZE INTO identifier-3 [END-STRING]

36 16-36 STRING Statement identifier-1 or literal-1 is field or value to be combined identifier-3 is field in which all identifiers or literals are combined DELIMITED BY clause –Transmitting of characters ends when value of identifier-2 or literal-2 encountered –SIZE means entire contents to be copied

37 16-37 STRING Example String First-Name Delimited By ' ' Middle-Name Delimited By ' ' Last-Name Delimited By ' ' Into Name-Out Copies characters from named fields to Name-Out up to first blank in field Name-Out is THOMASALVAEDISON

38 16-38 STRING Example To insert a blank between parts of name String First-Name Delimited By ' ' ' ' Delimited By Size Middle-Name Delimited By ' ' ' ' Delimited By Size Last-Name Delimited By ' ' Into Name-Out Places blank after each field

39 16-39 OVERFLOW Option Specifies operation(s) to be performed if receiving field not large enough to accommodate result NOT ON OVERFLOW option may also be used END-STRING scope terminator also available

40 16-40 POINTER Option To count number of characters moved in STRING statement Increments specified field by one for every character moved

41 16-41 POINTER Option Example Move 1 To WS-Count String First-Name Delimited By ' ' Into Name-Out With Pointer WS-Count If First-Name is 'Paul', WS-Count is five after STRING Subtract one from WS-Count to get length of actual move (4)

42 16-42 POINTER Option Also used to move data to receiving field beginning at some point other than first position If WS-Count initialized to 15 before STRING, First-Name moved to Name- Out beginning with fifteenth position of Name-Out

43 16-43 STRING Statement Rules DELIMITED BY clause required Receiving field must be elementary data item - no editing symbols or JUSTIFIED RIGHT clause All literals must be nonnumeric Identifier with POINTER clause must be elementary Moves data left to right but does not pad with low-order blanks

44 16-44 UNSTRING Statement To separate a field into its components Suppose Name-In equals TAFT, WILLIAM, H The last name, first name and middle initial can be stored in separate fields without commas with the following UNSTRING statement

45 16-45 UNSTRING Example Unstring Name-In Delimited By ',' Into Last-Name First-Name Middle-Initial TAFT will be stored in Last-Name, William in First-Name and H in Middle- Initial

46 16-46 UNSTRING Statement Format UNSTRING identifier-1 DELIMITED BY [ALL] identifier-2 literal-1 OR [ALL] identifier-3 literal-2… INTO identifier-4 … [END-UNSTRING]

47 16-47 UNSTRING Statement Sending field, as well as literal, must be nonnumeric Receiving fields may be numeric or nonnumeric ALL phrase means one or more occurrences of literal or identifier treated as one POINTER and OVERFLOW clauses may also be used

48 16-48 Chapter Summary COPY Statement To copy entries stored in a library to a user program Entries for ENVIRONMENT, DATA, and PROCEDURE DIVISIONs may be copied

49 16-49 Chapter Summary COPY statement most often used for Copying standard file and record description entries Modules used in PROCEDURE DIVISION

50 16-50 Chapter Summary CALL Statement To call or reference entire programs stored in a library Calling program is user program Called program (subprogram) is program accessed from library

51 16-51 Chapter Summary To pass data between calling program and called program CALL statement must include USING clause listing name of fields being passed PROCEDURE DIVISION statement of called program must also have USING clause Called program must have LINKAGE SECTION defining fields passed Identifiers in calling and called program may be same or different

52 16-52 Chapter Summary STRING statement joins or concatenates fields or portions of fields into one field UNSTRING statement breaks a long string into parts and thus enables processing of portion of sending field

53 16-53 Copyright © 2003 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in Section 117 of the 1976 United States Copyright Act without the express written permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages, caused by the use of these programs or from the use of the information contained herein.

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