Structured COBOL Programming

Structured COBOL Programming
“Copyright @ 2000 John Wiley & Sons, In. 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 permission of the copyright owner is unlawful. Request for further information should be addressed to the permissions Department , John Wily & 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.” Nancy Stern Hofstra University Robert A. Stern Nassau Community College 9th Edition PowerPoint Presentation: Richard H. Baum, Ph.D. DeVry Institute of Technology

Structured COBOL Programming, Stern & Stern, 9th Edition
CHAPTER 16 Improving Program Performance Using The COPY, CALL, and Other Statements Structured COBOL Programming, Stern & Stern, 9th Edition

OBJECTIVES To familiarize you with: 1. The COPY statement for copying parts of a program that are stored in a library. 2. The CALL statement for executing called programs as subroutines. 3. Text manipulation with the STRING and UNSTRING statements. Structured COBOL Programming, Stern & Stern, 9th Edition

CONTENTS COPY STATEMENT Introduction Entries that Can be Copied An Example The Full Format for the COPY Statement Self-Test CALL STATEMENT Why Use a CALL Statement? Format of the CALL Statement Called Program Requirements Calling Program Requirements Structured COBOL Programming, Stern & Stern, 9th Edition

CONTENTS Text Manipulation with the STRING and UNSTRING Statements The STRING Statement The Basic Format OVERFLOW Option POINTER Option General Rules for Using the STRING The UNSTRING Statement General Rules for Using the UNSTRING Structured COBOL Programming, Stern & Stern, 9th Edition

COPY STATEMENT A COPY statement is used to bring into a program a series of prewritten COBOL entries that have been stored in a library. Benefits of copy libraries include: (1) Saving the programmer a considerable amount of coding and debugging time; (2) Promoting program standardization since all programs that copy entries from a library will be using common data-names and/or procedures; Structured COBOL Programming, Stern & Stern, 9th Edition

COPY STATEMENT (3) Reducing the time it takes to make modifications and reducing duplication of effort; if a change needs to be made to a data entry, it can be made just once in the library without the need to alter individual programs; (4) Providing extensively annotated library entries that they are meaningful to all users; this annotation results in better-documented programs and systems. Structured COBOL Programming, Stern & Stern, 9th Edition

COPY STATEMENT Most often, the COPY statement is used to copy FD and 01 entries that define and describe files and records. In addition, standard modules to be used in the PROCEDURE DIVISION of several programs may also be stored in a library and copied as needed. Structured COBOL Programming, Stern & Stern, 9th Edition

COPY STATEMENT An Example:--Creating a library entry called CUSTOMER To copy CUSTOMER into a source program code the following : COPY CUSTOMER Structured COBOL Programming, Stern & Stern, 9th Edition

COPY STATEMENT The source listing might appear as follows(lower case is the copied library; the numbers are source line numbers; the lines that include a C after the line number are the copied statements): 1 IDENTIFICATION DIVISION. 2 PROGRAM-ID. CUST01. . . . 10 DATA DIVISION. 11 FD CUSTFILE LABEL RECORDS ARE STANDARD. 12 COPY CUSTOMER. 13 c 01 customer-rec. 14 c 05 cust-no pic x(5). 15 c 05 cust-name pic x(20). 16 c 05 cust-address pic x(30). 17 c 05 cust-bal-due pic 9(4)v99. Structured COBOL Programming, Stern & Stern, 9th Edition

The Full Format for the COPY Statement
COPY text-name-1 [{OF}{IN} library-name-1] [REPLACING {{==pseudo-text-1==} {identifier-1}{literal-1} {word-1} BY{==pseudo-text-2} {identifier-2}{literal-2}{word-2}. . . ] If the REPLACING clause is omitted from the COPY statement, the library text is copied unchanged. The REPLACING option allows virtually any library entry to be changed when it is being copied into the user's source program. Structured COBOL Programming, Stern & Stern, 9th Edition

The Full Format for the COPY Statement
The REPLACING clause does not alter the prewritten entries in the library. That is, the changes are made to the user's source program only. Typically, FDs with long or complex record descriptions are copied into programs, as are SCREEN SECTIONs and even modules or paragraphs that are common to more than one program. Tables are also often copied. Structured COBOL Programming, Stern & Stern, 9th Edition

QUESTIONS? Structured COBOL Programming, Stern & Stern, 9th Edition

SELF-TEST 1. A single series of file or record description entries may be used in several different programs by placing it in a _____ and _____ it when needed. Solution: library; copying Structured COBOL Programming, Stern & Stern, 9th Edition

SELF-TEST 2. With the statement _______you can include prewritten entries in your program. Solution: COPY Structured COBOL Programming, Stern & Stern, 9th Edition

SELF-TEST 3. (T or F) A user or source program can copy library routines and make changes to the field-names initially specified in the library. Solution: T Structured COBOL Programming, Stern & Stern, 9th Edition

SELF-TEST 4. (T or F) Using the REPLACING option of the COPY statement, it is possible to alter the field-names stored in the library itself. Solution: F--This option only alters library functions for the user program Structured COBOL Programming, Stern & Stern, 9th Edition

SELF-TEST 5. Two purposes of using library functions are to _____ and to ____ . Solution: make coding and debugging easier; increase standardization Structured COBOL Programming, Stern & Stern, 9th Edition

CALL STATEMENT Why Use the CALL Statement? Structured programs should consist of a series of independent modules that are executed from the main module. Modules within a program can be viewed as subroutines that are called or executed from the main module. But a program may also CALL or reference independent subprograms stored in a library that are entirely separate from the main program. Structured COBOL Programming, Stern & Stern, 9th Edition

CALL STATEMENT The program that references--or calls--a subprogram is referred to as the calling program. The subprogram that is linked and executed within the calling program is the called program. Structured COBOL Programming, Stern & Stern, 9th Edition

WHY USE A CALL STATEMENT?
The called program would need to be compiled, debugged, and catalogued or stored in a library so that it may be called when needed. Typical subprograms that may be used by numerous calling programs include edit routines, error control checks, standard calculations, and summary and total printing. Structured COBOL Programming, Stern & Stern, 9th Edition

ADVANTAGES OF CALLING SUBPROGRAMS
1. Avoids duplication of effort. When modules need to be included in more than one program, it is best to write them separately and call them into each program as needed. 2. Improves programmer productivity. Programmers can specialize or code modules that make use of their specific talents or skills. Structured COBOL Programming, Stern & Stern, 9th Edition

ADVANTAGES OF CALLING SUBPROGRAMS
3. Provides greater flexibility. Subprograms may be written in any programming language, but are typically written in a language best suited to the specific task required. 4. Allows changes to the called program to be made without needing to modify the calling program. 5. Results in greater standardization. Structured COBOL Programming, Stern & Stern, 9th Edition

Differences between CALL and COPY
The COPY brings into a user program separate ENVIRONMENT, DATA, or PROCEDURE DIVISION segments as is. The copied entries are compiled and executed together with the source program. The CALL causes an entire program, which is already in machine language, to be executed. The calling and called programs are separate, but data may be passed from the called program to the calling program or from the calling program to the called program. Structured COBOL Programming, Stern & Stern, 9th Edition

Differences between CALL and COPY
When the CALL is performed, data is passed from the calling to the called program. The entire called program is executed, data is passed from the called program back to the calling program, and control returns to the calling program. Typically, we COPY ENVIRONMENT and DATA DIVISION entries into a source program and we CALL programs from a library rather than COPY them. Structured COBOL Programming, Stern & Stern, 9th Edition

Format of the CALL Statement
CALL literal-1 [USING identifier-1....] Literal-1 is the name of the called program as specified in its PROGRAM-ID statement; it is enclosed in quotes like a nonnumeric literal. The USING clause of the CALL statement is required if the subprogram performs any operations in which data is to be passed from one program to another. Structured COBOL Programming, Stern & Stern, 9th Edition

Format of the CALL Statement
The CALL ... USING identifies fields in the main or calling program that will be either passed to the called program before it is executed, or passed back to the calling program after the called program has been executed. Since the purpose of calling a subprogram is to perform operations or calculations on data, we almost always employ the USING option. Structured COBOL Programming, Stern & Stern, 9th Edition

Called Program Requirements
PROGRAM-ID. The literal used in the CALL statement of the main program to extract a subprogram or routine from a library and execute it must be identical to the called program's PROGRAM-ID. In the calling program, we code CALL 'literal-1' USING ... . In the called program, we code PROGRAM-ID. literal-1. Structured COBOL Programming, Stern & Stern, 9th Edition

LINKAGE SECTION. A LINKAGE SECTION must be defined in the called program for identifying those items that: (1) will be passed to the called program from the calling program and (2) passed back from the called program to the calling program. The LINKAGE SECTION of the called program, then, describes all items to be passed between the two programs. Structured COBOL Programming, Stern & Stern, 9th Edition

PROCEDURE DIVISION USING. The identifiers specified in the USING clause in the PROCEDURE DIVISION entry include all fields defined in the LINKAGE SECTION; these identifiers will be passed from one program to the other. They are passed to and from corresponding identifiers in the CALL ... USING of the main program. Structured COBOL Programming, Stern & Stern, 9th Edition

EXIT PROGRAM. The last executed statement in the called program must be the EXIT PROGRAM. It signals the computer to return control back to the calling program. Structured COBOL Programming, Stern & Stern, 9th Edition

Calling Program Requirements
To execute a subprogram stored in a library, the only statement required in the calling program is the CALL 'literal-1' USING . . . The literal specified in the CALL statement of the main program should be the same as in the PROGRAM-ID of the called program, but it is enclosed in quotes in the CALL. Structured COBOL Programming, Stern & Stern, 9th Edition

With COBOL 74, you pass 01-level items. With COBOL 85 you can pass parameters at any level as long as they are elementary items. Structured COBOL Programming, Stern & Stern, 9th Edition

TEXT MANIPULATION WITH THE STRING AND UNSTRING STATEMENTS
Structured COBOL Programming, Stern & Stern, 9th Edition

Interactive Processing
When data is entered interactively, we sometimes need to convert it into a more concise form for processing purposes or for storing it on disk. Similarly, when data is to be displayed, we sometimes need to convert it from a concise form to a more readable form. We can use the STRING and UNSTRING for these purposes. Structured COBOL Programming, Stern & Stern, 9th Edition

The STRING Statement The Basic Format A STRING statement may be used to combine several fields to form one concise field. This process is called concatenation. Structured COBOL Programming, Stern & Stern, 9th Edition

The STRING Statement A simplified format of the STRING statement is: STRING {{identifier-1}{literal-1} . . . DELIMITED BY {identifier-2} {literal-2}{SIZE}} . . . INTO identifier-3 [END-STRING] Structured COBOL Programming, Stern & Stern, 9th Edition

The STRING Statement For example, we can instruct the computer to transmit only significant or nonblank characters in FIRST-NAME, MIDDLE-NAME, and LAST-NAME. Once a blank is reached, we stop transmitting that field: STRING FIRST-NAME DELIMITED BY ' ' MIDDLE-NAME DELIMITED BY ' ' LAST-NAME DELIMITED BY ' ' INTO NAME-OUT The delimiter itself would not be placed in the receiving field. Structured COBOL Programming, Stern & Stern, 9th Edition

The STRING Statement We can also use literals between clauses, to insert blanks between significant characters as follows: STRING FIRST-NAME DELIMITED BY ‘ ‘ ‘ ‘ DELIMITED BY SIZE MIDDLE-NAME DELIMITED BY ‘ ‘ LAST-NAME DELIMITED BY ‘ ‘ INTO NAME In this instance the NAME would be displayed as: THOMAS ALVA EDISON Structured COBOL Programming, Stern & Stern, 9th Edition

The STRING Statement The delimiter SIZE means that the entire content of the specified literal is transmitted (it could have been a field as well). Each time ' ' DELIMITED BY SIZE is executed, a one-position blank is transmitted. Structured COBOL Programming, Stern & Stern, 9th Edition

The STRING Statement As noted, the delimiter SIZE means that the entire content of the field is transmitted. The delimiter for STATE and ZIP can also be SIZE because we will always print two characters for STATE and five characters for ZIP. Note that this coding would not be correct if city consisted of more than 1 word ( NEW ORLEANS). Structured COBOL Programming, Stern & Stern, 9th Edition

The STRING Statement There are numerous additional options available with the STRING, only some of which we will discuss. OVERFLOW Option STRING... [ON OVERFLOW imperative statement-1] The OVERFLOW option specifies the operation(s) to be performed if the receiving field is not large enough to accommodate the result. Structured COBOL Programming, Stern & Stern, 9th Edition

The STRING Statement POINTER Option We may also count the number of characters actually moved in a STRING statement: STRING ... [WITH POINTER identifier- 1] [ON OVERFLOW ...] The identifier will specify the number of nonblank characters moved to the receiving field if it is initialized at one. Structured COBOL Programming, Stern & Stern, 9th Edition

The STRING Statement RULES FOR USING THE STRING STATEMENT 1. The DELIMITED BY clause is required. It can indicate: SIZE: The entire sending field is transmitted. Literal: The transfer of data is terminated when the specified literal is encountered; the literal itself is not moved. Identifier: The transfer of data is terminated when the contents of the identifier is encountered. Structured COBOL Programming, Stern & Stern, 9th Edition

The STRING Statement 2. The receiving field must be an elementary data item with no editing symbols or JUSTIFIED RIGHT clause. 3. All literals must be described as nonnumeric. Structured COBOL Programming, Stern & Stern, 9th Edition

The STRING Statement 4. The identifier specified with the POINTER clause must be an elementary numeric item. 5. The STRING statement moves data from left to right just like alphanumeric fields are moved, but a STRING does not pad with low-order blanks, unlike an alphanumeric MOVE. Structured COBOL Programming, Stern & Stern, 9th Edition

THE UNSTRING STATEMENT
The Basic Format The UNSTRING statement may be used to convert keyed data to a more appropriate form for storing it on disk. For example, a program may include a statement that causes the following to be displayed on a screen: ENTER NAME: LAST, FIRST, MIDDLE INITIAL : USE COMMAS TO SEPARATE ENTRIES The message to the operator is fairly clear. When the name is entered, is stored in an alphanumeric field called NAME- IN. Structured COBOL Programming, Stern & Stern, 9th Edition

Suppose we wish to store the name in an output disk record as follows: 01 PAYROLL-REC. 05 NAME-OUT. 10 LAST-NAME PIC X(20). 10 FIRST-NAME PIC X(15). 10 MIDDLE-INITIAL PIC X. Structured COBOL Programming, Stern & Stern, 9th Edition

With an UNSTRING statement, we can instruct the computer to separate the NAME-IN into its components and store them without the commas: UNSTRING NAME-IN DELIMITED BY ‘,’ INTO LAST-NAME FIRST-NAME MIDDLE-INITIAL Structured COBOL Programming, Stern & Stern, 9th Edition

UNSTRING Format UNSTRING identifier-1 [DELIMITED BY [ALL]{identifier-2}{literal-1} [OR [ALL] {identifier-3}{literal-2}]...] INTO identifier-4... [END-UNSTRING] Structured COBOL Programming, Stern & Stern, 9th Edition

We may use any literal, even a blank, as a delimiter. We may also ACCEPT a name from a keyboard and UNSTRING it so that we can use just the last name for looking up a corresponding disk record with last name as a RECORD KEY or ALTERNATE RECORD KEY. When the ALL phrase is included, one or more occurrences of the literal or identifier are treated as just one occurrence. Structured COBOL Programming, Stern & Stern, 9th Edition

SUMMARY RULES FOR USING THE UNSTRING STATEMENT 1. The sending field must be nonnumeric. The receiving fields may be numeric or nonnumeric. 2. Each literal must be nonnumeric. 3. The [WITH POINTER identifier] and [ON OVERFLOW imperative-statement] clauses may be used in the same way as with the STRING. Structured COBOL Programming, Stern & Stern, 9th Edition

CHAPTER SLIDES END HERE
CHAPTER SUMMARY COMES NEXT Structured COBOL Programming, Stern & Stern, 9th Edition

CHAPTER SUMMARY A. COPY Statement 1. To copy entries stored in a library to a user program. 2. ENVIRONMENT, DATA, and PROCEDURE DIVISION entries may be copied. 3. Most often used for copying standard file and record description entries or modules to be used in the PROCEDURE DIVISION. 4. The format is: COPY text-name {OF}{IN} library-name. Structured COBOL Programming, Stern & Stern, 9th Edition

CHAPTER SUMMARY B. CALL Statement 1. To call or reference entire programs stored in a library. 2. The user program is referred to as the calling program; the program accessed from the library will serve as a subprogram and is referred to as the called program. 3. To pass data from the called program to the calling program. a. The CALL statement can include a USING clause that lists the names of the fields in the calling program that are passed to the called program and fields that will be passed back from the called program. Structured COBOL Programming, Stern & Stern, 9th Edition

CHAPTER SUMMARY b. The PROCEDURE DIVISION statement of the called program also includes a USING clause to indicate identifiers specified in this subprogram that will correspond to identifiers in the calling program. c. Identifiers in the called and calling program may be the same or they may be different, but their picture clauses should match. d. The called program must have a LINKAGE SECTION in which fields to be passed to and from the calling program are defined. This is the last section of the DATA DIVISION. Structured COBOL Programming, Stern & Stern, 9th Edition

CHAPTER SUMMARY e. The called program must end with an EXIT PROGRAM statement. This must be in a separate paragraph only for COBOL 74. C. The STRING statement joins or concatenates fields or portions of fields into one field. The UNSTRING statement enables processing of a portion of a sending field. Structured COBOL Programming, Stern & Stern, 9th Edition

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