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Using The COPY, CALL, STRING , UNSTRING STATEMENTS

Chapter 16. Using The COPY, CALL, STRING , UNSTRING STATEMENTS. 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.

sydney-greer
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Using The COPY, CALL, STRING , UNSTRING STATEMENTS

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  1. Chapter 16 Using The COPY, CALL, STRING , UNSTRINGSTATEMENTS

  2. 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

  3. 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

  4. 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

  5. COPY Statement Format COPY test-name OF library-name. IN • Use in ENVIRONMENT, DATA, or PROCEDURE DIVISION • Library-name is external-name, 1 to 8 characters, letters and digits only • We’ll have to check to see how to create library on the alpha

  6. COPY Statement Example • Suppose file called Customer, stored in library contains following entries: 01 Customer-Rec. 05 Cust-No Pic X(5). 05 Cust-Name Pic X(20). 05 Cust-Address Pic X(30). 05 Cust-Bal-Due Pic 9(4)V99.

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

  8. Source Listing with COPY … ... 11 FD CustFile. 12 Copy Customer. 13C 01 Customer-Rec. 14C 05 Cust-No Pic X(5). 15C 05 Cust-Name Pic X(20). 16C 05 Cust-Address Pic X(30). 17C 05 Cust-Bal-Due Pic 9(4)V99. Line numbers followed by C are copied statements

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

  10. Changing COPYed Entries Example Copy Customer Replacing Cust-No By Cust-Number, ==X(5)== By ==X(6)==. • Changes copied line 14C • From: 14C 05 Cust-No Pic X(5). • To: 14C 05 Cust-Number Pic X(6).

  11. 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

  12. 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

  13. 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

  14. 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 • COPY is like include in C • CALL is like a function

  15. CALL vs COPY • Typically, COPY ENVIROMENT, DATA DIVISION entries into source program • CALL subprograms in PROCEDURE DIVISION rather than COPY them

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

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

  18. 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 Same as other languages

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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

  24. 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

  25. Subprogram Example Identification Division. Program-ID. FICAProg. Data Division. Linkage Section. 01 WS-Ann-Sal Pic 9(6). 01 Soc-Sec Pic 9(4)V99. 01 Med-Tax Pic 9(5)V99.

  26. 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.

  27. 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

  28. 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

  29. Parameter Correspondence • Data-names of corresponding parameters may be same or different • Parameters paired by sequence, not by data-name (same as C) • List parameters in same order in both USING clauses

  30. 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

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

  32. STRING Statement • Suppose name fields have values below • Print name with single blank between parts: THOMAS ALVA EDISON

  33. STRING Statement Format STRING identifier-1 ... literal-1 identifier-2 DELIMITED BY literal-2 ... SIZE INTO identifier-3 [END-STRING]

  34. 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

  35. 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

  36. 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

  37. 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

  38. POINTER Option • To count number of characters moved in STRING statement • Increments specified field by one for every character moved • If you need to know how may characters were concatenated

  39. 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) • Initialize WS-Count to 1 or 0

  40. 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

  41. 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

  42. 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

  43. 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

  44. UNSTRING Statement Format UNSTRING identifier-1 DELIMITED BY [ALL] identifier-2 literal-1 OR[ALL] identifier-3 literal-2 … INTOidentifier-4 … [END-UNSTRING]

  45. 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

  46. 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

  47. Chapter Summary COPY statement most often used for • Copying standard file and record description entries • Modules used in PROCEDURE DIVISION

  48. 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

  49. 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

  50. 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

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