TABLES chp. 12

1
TABLES (chp. 12)

• group of storage locations (i.e. elements) with
  the same name
• accessed by name and subscript ex. var-name
  (sub)
• similar to arrays in other languages

2
OCCURS Clause

• Defines the number of elements in the table for
  each level
• Defines the maximum subscript for each level
• Up to seven levels of OCCURS permitted in COBOL
• Can not be used on 01 level item

SUBSCRIPTS

• Integer values from 1 to occurs clause value
  (specifies maximum value)
• Up to 7 subscripts are permitted in COBOL
• Subscripts are listed in parenthesis following
  the table name
• Each time the value of a subscript changes,
  data-name (sub) refers to a different element in
  the array
• Using a data-name as a subscript enables its
  contents to be varied
• Relative subscripting is used when what is in
  parenthesis can be an arithmetic expression
• if using subscript constants (named or literal)
  compiler will detect error
• if using subscript variables, error won't be
  detected until run-time

3
TABLE examples
If item defined by OCCURS has PIC clause, it
defines a series of elementary items 01 Totals.
05 Month-Totals Occurs 12 Times Pic 9(5)V99.
For your information When a variable name has an
OCCURS clause on it or above it with a smaller
level number, it must have one subscript when
referencing that memory location for each OCCURS.
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TABLE examples
Identifier used with OCCURS may also be group
item 01 Tax-Table. 05 Group-X Occurs 20
Times. 10 City Pic X(6). 10
Tax-Rate Pic V999.
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More TABLE examples
EXAMPLE 1 01 DAYS-OF-MONTH-TABLE.          
03 MONTHS     OCCURS 12 times.
                 05 Month-Name       PIC X(15).
                 05 Month-Num-Days PIC 99. Move
January to Month-Name (1) Move 31 to
Month-Num-Days (1) EXAMPLE 2 01
DAYS-OF-MONTH-TABLE.                  05
Month-Name   PIC X(15) OCCURS 12
TIMES.            05 Month-Num-Days PIC 99
OCCURS 12 TIMES. Move January to Month-Name
(1) Move 31 to Month-Num-Days (1)
How else initialize Month-Name and
Month-Num-Days?!
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One More TABLE example
01 GRADE-TABLE. 05 QUIZ-TABLE OCCURS 40
TIMES. 10 QUIZ1 PIC 9(2). 10 QUIZ2 PIC 9(2).
10 QUIZ3 PIC 9(2). 10 QUIZ4 PIC 9(2). ? How
do we average all the quiz scores for QUIZ4?
Compute-Average-Quiz4. MOVE ZERO TO
Total-Grade MOVE 1 TO Sub PERFORM UNTIL Sub gt
Num-Quizzes ADD QUIZ4(Sub) TO Total-Grade
ADD 1 TO Sub END-PERFORM DIVIDE
Total-Grade BY Num-Quizzes GIVING
Average-Score
Convert to Perform-Varying
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INITIALIZING TABLES
Two ways to use VALUE clause to initialize all
elements to zero 01 Array-1 Value Zero.
05 Totals Occurs 50 Times Pic 9(5). 01
Array-1. 05 Totals Occurs 50 Times Pic
9(5) Value Zero. Can also initialize each
element to different value 01 Day-Names Value
'SUNMONTUEWEDTHUFRISAT'. 05 Days Occurs
7 Times Pic X(3). ??? Can an initialization be
done on the 05 directly above??? INITIALIZE
STATEMENT (i.e. in Procedure Division) A series
of elementary items contained within a group item
can all be initialized. Numeric items will be
initialized to zero and nonnumeric items will be
initialized to blank. FORMAT INITIALIZE
identifier-1
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REDEFINES
Purpose Used to define a field with a value
clause then redefine it as an array. However,
you cannot do the reverse that is, once an entry
has been defined by an OCCURS clause, it may NOT
be redefined. FORMAT in Data Division L
identifier-1 REDEFINES identifier-2 finish
declaration where L means level
number Identifier-1 and identifier-2 must be on
the same level EXAMPLES See table example
program 01 Rates. 05 10Rate PIC 99V999
value 12.345. 05 100Rate REDEFINES 10Rate
PIC 999V99. 05 1000Rate REDEFINES 10Rate
PIC 9999V9. Result ? 100Rate 123.45 and
1000Rate 1234.5
01 HoldDate. 02 EuroDate. 03 EuroDay
PIC 99 value 11. 03 EuroMonth PIC 99
value 3. 03 EuroYear PIC 9(4) value
2003. 02 USDate REDEFINES EuroDate. 03
USMonth PIC 99. 03 USDay PIC
99. 03 USYear PIC 9(4). USMonth 3
and USDay 11
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2 dimensional TABLES (ex1)
Define array as follows 01 Temperature-Array.
05 Day-In-Week Occurs 7 Times. 10 Hour
Occurs 24 Times. 15 Temp Pic 9(3).
For your information If reading in from file,
what does input file look like?! FD input
file 01 input-rec pic 999. Find the average temp
for each day. Find the average temp for each
hour. PARTICIPATION POINTS (5) (due in one week
graded on if works!) What if have negative
temperatures? How solve?! That is, what does
input file look like? What does declaration look
like?
Perform a from 1 by 1 until a gt 7 perform b
from 1 by 1 until b gt 24 read input-file at
end.. move input-rec to temp (a
b) end-perform End-perform
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2 dimensional TABLES (ex2)
01 Jeans-Table. 05 Jean-Gender OCCURS 2
TIMES. 10 Jean-Color OCCURS 3
TIMES. 15 Jean-SalesValue PIC
9(8)V99. 15 Jean-NumSold
PIC 9(7).
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2 dimensional TABLES (ex3)
01 Jeans-Table. 05 Jean-Size OCCURS 10
TIMES. 10 Exact-Size PIC 99.
10 Jean-Style PIC X. 10
Jean-Color OCCURS 3 TIMES. 15
Jean-SalesValue PIC 9(8)V99. 15
Jean-NumSold PIC 9(7).