Chapter 11

Introduction to Tables

Tables / Arrays - A Matter of Semantics

Arrays used to store multiple occurrences of a set data items Can represent data in an input/output record Used in working storage to establish a set of like accumulators

Tables used to retrieve some reference value need for processing

Both handled the same way in programming

Problem - Represent 12 Months Sales

01 ANNUAL-SALES-DATA. 05 JAN-SALES PIC 9(6). 05 FEB-SALES PIC 9(6). 05 MAR-SALES PIC 9(6). 05 APR-SALES PIC 9(6). 05 MAY-SALES PIC 9(6). 05 JUN-SALES PIC 9(6). 05 JUL-SALES PIC 9(6). 05 AUG-SALES PIC 9(6). 05 SEP-SALES PIC 9(6). 05 OCT-SALES PIC 9(6). 05 NOV-SALES PIC 9(6). 05 DEC-SALES PIC 9(6).

Accumulate Total-Sales

COMPUTE TOTAL-SALES = JAN-SALES + FEB-SALES + MAR-SALES + APR-SALES + MAY-SALES + JUN-SALES +

JUL-SALES + AUG-SALES + SEP-SALES + OCT-SALES + NOV-SALES + DEC-SALES

Is there a better way?

•Occurs Clause

Provides for grouping similar data Represents multiple occurrences same type Format is the same (ie. Picture) for each item

Allows use of same data name Individual data items identified by a

subscript or indexOCCURS integer TIMESCannot be used at 01 level

The Table Concept

01 ANNUAL-SALES-DATA. 05 SALES OCCURS 12 TIMES PIC 9(6).

(b) OCCURS Clause

ANNUAL-SALES-DATA

SALES (1) SALES (2) SALES (12)

. . .

(c) Memory Storage Schematic

Figure 11.1 The Table Concept01 ANNUAL-SALES-DATA. 05 JAN-SALES PIC 9(6). 05 FEB-SALES PIC 9(6). 05 MAR-SALES PIC 9(6). 05 APR-SALES PIC 9(6). 05 MAY-SALES PIC 9(6). 05 JUN-SALES PIC 9(6). 05 JUL-SALES PIC 9(6). 05 AUG-SALES PIC 9(6). 05 SEP-SALES PIC 9(6). 05 OCT-SALES PIC 9(6). 05 NOV-SALES PIC 9(6). 05 DEC-SALES PIC 9(6).

(a) Brute Force

01 ANNUAL-SALES-DATA. 05 SALES OCCURS 12 TIMES PIC 9(6).

(b) OCCURS Clause

ANNUAL-SALES-DATA

SALES (1) SALES (2) SALES (12)

. . .

(c) Storage Schematic

PERFORM VARYING

PERFORM [procedure name]

[WITH TEST {BEFORE/ AFTER}] <= BEFORE is Default

VARYING identifier-1 FROM {literal-1 / identifier-2}

BY {literal-2 / identifier-3}

UNTIL condition-1

[imperative-statement(s) END-PERFORM

identifier-1 define in ws - we refer to it as a subscript{literal-1 / identifier-2} an integer value defining starting point{literal-2 / identifier-3} an integer value defining increment amount

PERFORM VARYING steps (with TEST BEFORE)

Initializes the variableTests the conditionEnters the loopIncrements the variableRetests the variable

Figure 11.2 PERFORM VARYING (with TEST BEFORE)

Initializeidentifier-1

to FROM value

Evaluatecondition=1

Performprocedure-1

or imperative-statement

Incrementidentifier-1

with BY value

TRUE

FALSE

Figure 11.3 Processing a Table

MOVE ZERO TO ANNUAL-TOTAL.PERFORM 400-INCREMENT-ANNUAL-TOTAL

VARYING SALES-SUB FROM 1 BY 1UNTIL SALES-SUB > 12.

. .400-INCREMENT-ANNUAL-TOTAL.

ADD SALES (SALES-SUB) TO ANNUAL-TOTAL.

(a) Performing a Paragraph

MOVE ZERO TO ANNUAL-TOTAL.PERFORM

VARYING SALES-SUB FROM 1 BY 1UNTIL SALES-SUB > 12

ADD SALES (SALES-SUB) TO ANNUAL-TOTALEND-PERFORM.

(b) In-line Perform

Problem Definition

We need to define a group of data items that repeat - such as

Salaryand Salary effective date

Want to keep track of current salary and previous threesalaries

05 SALARY-DATA OCCURS 4 TIMES.10 SALARY PIC 9(6)V99.10 SAL-DATE PIC 9(4).

Figure 11.4 OCCURS Clause at the Group Level

SALARY-DATA (2)

SALARY (2) SAL-DATE (2)

SALARY-DATA (1)

SALARY (1) SAL-DATE (1)

SALARY-DATA (3)

SALARY (3) SAL-DATE (3)

(a) COBOL Statements

(b) Storage Schematic

05 SALARY-DATA. 10 SALARY OCCURS 4 TIMES PIC 9(6)V99.10 SAL-DATE OCCURS 4 TIMES PIC 9(4).

Figure 11.5 OCCURS Clause at the Elementary Level

SALARY (2) SAL-DATE (2)

SALARY-DATA

SALARY (1) SAL-DATE (1) SAL-DATE (3)SALARY (3)

(b) Storage Schematic

(a) COBOL Statements

SUBSCRIPTS

Defined in WORKING-STORAGEUSAGE COMP - internal

representation binarySyntax

DATE (2) or DATE (Month-No)Relative Subscripting

BONUS (YEARS + 2)

CAVEATS

Data defined with an OCCURS must be referenced with a subscript or index

Syntax error if no subscript usedRuntime error if subscript 0 or

greater than table size

SALARY REPORT FORXXXXXXXXXXXXXXXXXXXXXXXXXXXX

CURRENT SALARY EFFECTIVE DATE PERCENT INCREASE $46,000 09/93 15.0% $40,000 09/92 11.1% $36,000 09/91 12.5% $32,000 09/90

Report Specifications

(b) Computation of Percent Salary Increase

PERFORM VARYING SUB FROM 1 BY 1UNTIL SUB > 3 OR SALARY (SUB + 1) = 0 COMPUTE PCT-SALARY-INC (SUB)

= 100 * ((SALARY (SUB) - SALARY (SUB+1)) / SALARY (SUB + 1)

END-COMPUTEEND-PERFORM

Figure 11.6 Relative Subscripting

OCCURS DEPENDING ON

Variable length records

OCCURS {integer-1 TO integer-2} DEPENDING ON data-name

FD STUDENT-TRANSCRIPT-FILE RECORD CONTAINS 42 TO 1131 CHARACTERS DATA RECORD IS STUDENT-RECORD.01 STUDETN-RECORD. 05 ST-NAME PIC X(30). 05 ST-MAJOR PIC X(10). 05 ST-COURSES-COMPLETED PIC 99. 05 ST-COURSE-INFO

OCCURS 0 TO 99 TIMESDEPENDING ON ST-COURSES-COMPLETED.10 ST-COURSE-NUMBER PIC

9(6).10 ST-GRADE PIC X.10 ST-COURSE-DATE PIC 9(4).

Figure 11.7 Variable-length Records

Depending On

05 ST-COURSES-COMPLETED PIC 99. 05 ST-COURSE-INFO

OCCURS 0 TO 99 TIMES DEPENDING ON ST-COURSES-COMPLETED.10 ST-COURSE-NUMBER PIC 9(6).10 ST-GRADE PIC X.10 ST-COURSE-DATE PIC 9(4).

Figure 11.9 Calculation of Grade Point Average

COURSE COURSE GRADE COURSE CREDITS

Course Number 1 A 2 Course Number 2 B 4

(a) Hypothetical Grades

SUB GRADE (SUB) CREDITS (SUB) MULTIPLIER TOTAL-QUALITY-POINTS TOTAL-CREDITS 1 A 2 4 8 (0 + 2*4) 2 2 B 4 3 20 (8 + 4*3) 6

(b) Incrementing Counters

GRADE-POINT-AVERAGE = TOTAL-QUALITY-POINTS / TOTAL-CREDITS = 20 / 6 = 3.33

(c) Calculation of Grade Point Average

300-W RIT ET RANS

HEADING

410-INCREM ENTCOUNT ERS

420-W RIT EDET AIL

LINE

310-PROCESSCOURSES

320-W RIT EG PA

330-ADD T ODEANS

LIST

200-CREAT ET RANSCRIPT

340-W RIT EDEANS-LIST

HEADING

350-W RIT EDEANS-LIST

DET AILS

210-W RIT EDEANS

LIST

100-PROCESSST UDENTRECORDS

Figure 11.10 Hierarchy Chart for Transcript Program

Figure 11.11 Pseudocode for Transcript Program

Open filesDO WHILE data remains READ Student file AT END

Indicate no more data NOT AT END

Write transcript headingMove zero to quality-point and credit countersDO for each course Determine multiplier for this course Increment total quality points Increment total credit counter Write detail line for this courseENDDOCOMPUTE grade-point-average = total quality points /’ total creditsWrite grade-point-averageIF dean’s list IF students on dean’s list > 100

Display appropriate error message ELSE

Increment students on dean’s listMove this student to dean’s list table

END-IFEND-IF

ENDREADENDDOWrite heading for dean’s listDO for every student on dean’s list Write student dataENDDOClose filesStop run

INDEXES

Defined as part of the OCCURS clauseMore efficient than subscripts

OCCURS integer-1 TIMES [ASCENDING/DESCENDING KEY IS data-name][INDEXED BY index-name-1]

Used the same as a SubscriptRequires no other definitionMust use SET verb

Table 11.1 Indexes versus Subscripts

INDEXES SUBSCRIPTSDefined with a specific table; can be used Defined in Working-Storage; the same subscript only with the table with which they are defined can be used with multiple tables although this is not recommended

Initialized and incremented via the SET May not be used with SET statements (MOVE and can also be manipulated in ADD are used instead); can also be manipulated in

PERFORM statements

Provide more efficient object code than USAGE IS COMPUTATIONAL makes subscriptssubscripts more efficient, although indexes are still faster