2. Why Cobol?
• Billions of lines of existing code with more
added each year
• Designed for business
• Great compilers
• Runs fast
• Relatively simple to learn
• The language keeps evolving
3. Enterprise Cobol for zOS
IBM COBOL:
• http://www-01.ibm.com/software/awdtools/cobol/zos/
IBM COBOL Documentation:
• http://www-01.ibm.com/software/awdtools/cobol/zos/library/
Languagage Reference
• http://publibfp.boulder.ibm.com/epubs/pdf/igy3lr50.pdf
Programming Guide
• http://publibfp.boulder.ibm.com/epubs/pdf/igy3pg50.pdf
4. Program Organization
• Program – Organized like a book
• Division – Identification, Environment, Data, Procedure
• Section
• Paragraph
• Sentence
• Clause
• Phrase
• Word
6. Coding Rules
• Cols 1-6 – left blank. Compiler fills in with sequence numbers
• Col 7 – Usually blank,* means comment line, - is continuation, D for
debugging lines
• Cols 8-11 – “A” margin or Area A
• Cols 12-72 – “B” margin or Area B
• Cols 73-80 – unused
• 1 2 3 4 5 6|7| 8 9 10 11|12 13 …71 71 |
Seq Nos | | Area A | Area B |
8. Continuation of Literals
• Continue the constant through column 71
• Put a “-” in column 7
• Continue constant with a ‘ OR “
• Continue constant in area B
9. Things That Go in Area A
Area A items:
• Division headers
• Section headers
• Paragraph headers or paragraph names
• Level indicators or level-numbers (01 and 77)
• DECLARATIVES and END DECLARATIVES
• End program, end class, and end method markers
10. Things That Go in Area B
Area B items:
• Entries, sentences, statements, and clauses
• Continuation lines
11. Things That Go in A or B
• Area A or B
• Level-numbers
• Comment lines
• Compiler-directing statements
• Debugging lines
• Pseudo-text
13. IDENTIFICATION DIVISION
IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.
AUTHOR. JOE SMITH.
INSTALLATION. TSYS.
DATE-WRITTEN. 12/03/2011.
DATE-COMPILED. 12/03/2011.
• Only PROGRAM-ID is required
• Some interesting parms can be coded on the
PROGRAM-ID
14. ENVIRONMENT DIVISION
This division connects external DD file names with internal
file names.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT MSTRFILE ASSIGN TO MSTRFILE
SELECT CUSTOMER-FILE
ASSIGN TO CUSTMAST
ORGANIZATION IS INDEXED
ACCESS MODE IS RANDOM
RECORD KEY IS COSTOMER-KEY
FILE STATUS IS CUSTOMER-FILE-STATUS.
Internal File
Name
External DD
File Name
15. DATA DIVISION
• Used to create variables and constant fields
• Only three data types
– numeric PIC 99999.
– alphanumeric (text/string) PIC XXX.
– alphabetic PIC AAA.
• Level numbers indicate subordination of fields.
Use levels 01-49
• Alphabetic is seldom used
16. Level Numbers
• Group item – a subdivided field
• Elementary item – a non-subdivided field
• 01 – Group or independent item
• Higher numbers indicate subordinate fields
17. Level Numbers
• 66, 77, 88 have special significance
• 66 – Used to rename (no longer used)
• 77 – An independent item (choose 01)
• 88 – Condition name
19. Condition Names
• 01 TRAN-CODE PIC X.
88 GOOD VALUE ‘G’.
88 BAD VALUE ‘B’.
88 INDIFFERENT VALUE ‘I’.
…
SET GOOD TO TRUE
…
IF (GOOD) …
Equivalent to MOVE ‘G’ TO TRAN-CODE
Equivalent to IF TRAN-CODE = ‘G’
22. Picture Clauses
• Picture clause values usually use 9, X, V,
S, A
• 9 – a decimal digit
• X – any alphanumeric character
• V – an implied decimal point
• S – a sign
• A – A-Z, and blank
25. USAGE Clause
• Specifies the format in which data is stored in
memory
• Normally, the phrase “USAGE IS” is omitted
01 COST USAGE IS PACKED-DECIMAL PIC S9(5).
01 COST PACKED-DECIMAL PIC S9(5).
01 FIRST-NAME USAGE IS DISPLAY PIC X(20).
01 FIRST-NAME PIC X(20).
26. DATA DIVISION
We define data used in input-output operations.
FILE SECTION.
FD CUSTOMER-FILE.
01 CUSTOMER-MASTER.
05 CUST-NUM PIC 9(2).
05 CUST-FNAME PIC X(20).
05 CUST-LNAME PIC X(20).
FD SALES-REPORT.
01 REPORT-AREA PIC X(132).
28. EBCDIC
• EBCDIC is an IBM format for storing alphanumeric
characters
A - X’C1’ J - X’D1’
B - X’C2’ K - X’D2’ S – X’E2’
C - X’C3’ L - X’D3’ T – X’E3’
D - X’C4’ M - X’D4’ U – X’E4’
E - X’C5’ N - X’D5’ V – X’E5’
F - X’C6’ O - X’D6’ W – X’E6’
G - X’C7’ P - X’D7’ X – X’E7’
H - X’C8’ Q - X’D8’ Y – X’E8’
I - X’C9’ R - X’D9’ Z – X’E9’
29. EBCDIC
• EBCDIC is an IBM format for storing alphanumeric
characters
0 - X’F0’ SPACE – X’40’
1 – X’F1’ . - X’4B’
2 - X’F2’ , - X’6B’
3 – X’F3’ * - X’5C’
4 - X’F4’ - - X’60’
5 – X’F5’
6 - X’F6’
7 – X’F7’
8 – X’F8’
9 – X’F9’
30. BINARY DATA
• Stored in 2’s Complement format
• Leftmost bit is a sign ( 0 +, 1 - )
• If the number is positive, interpret it as plain binary
01011 = 8 + 2 + 1 = + 11
• If the number is negative, compute the complement –
Invert. (Change all 1’s to 0’s and 0’s to 1’s.) Add 1. The
result is the additive complement
31. BINARY DATA
• 10011 is a negative number.
Inverting we have 01100.
Adding 1 we have 01100 + 1 = 01101. This is a positive
number. 01101 8 + 4 + 1 = 13, so the original
number is -13.
32. BINARY DATA
• Declaring a data field as BINARY causes the
data to be stored in 2’s complement format.
• 01 X-FIELD PIC S9(4) BINARY VALUE -1.
• X-FIELD will contain
1111111111111111 = X’FFFF’.
• Binary data is processed in a register
33. PACKED-DECIMAL DATA
• Defining a field to be PACKED-DECIMAL or Computational-3
causes the data to be stored internally in a packed decimal format.
• There are 2 decimal digits stored in each byte. A sign is stored in
the rightmost “nibble”. (C +, D -)
• Y-FIELD PIC S999 VALUE -23 PACKED-DECIMAL.
produces a 2 byte field containing X’023D’
• Most business arithmetic occurs in packed decimal.
34. Packed No-Sign Data
• Packed no-sign data is a non-native data
type that was created to save space on a
disk when storing dates
• If the digits in a date like 10/23/89 were
stored in a packed field, the field would
require 4 bytes: 01|02|38|9C
• By removing the sign, the date fits in 3
bytes: 10|23|89
35. Packed No-Sign Data
• These type fields require special handling
in Cobol
• Program PKNOSIGN illustrates how a
displayable date can be recovered from a
packed no-sign field.
36. ZONED-DECIMAL DATA
• A numeric field which is described as DISPLAY, or in
which the usage clause is omitted, is stored in a zoned
decimal format.
• In zoned decimal, each digit takes up one byte, and a
sign is stored in the zone portion of the rightmost byte of
the field.
• Z-FIELD PIC S999 VALUE -32
produces a 3 byte field containing X’F0F3D2’.
37. ZONED-DECIMAL DATA
• Z-FIELD PIC S999 VALUE -32.
produces a 3 byte field containing X’F0F3D2’.
• Z-FIELD PIC S999 VALUE 32.
produces a 3 byte field containing X’F0F3C2’.
• W-FIELD PIC 999 VALUE 0.
MOVE -32 TO W-FIELD
produces a 3 byte field containing X’F0F3C2’.
38. DATA DIVISION
Define the data needed for internal processing in the
WORKING-STORAGE SECTION.
Storage is statically allocated and exists for the life of the
run unit.
WORKING-STORAGE SECTION.
01 TOTAL-FIELDS.
05 CUST-TOTAL PIC S9(7)V99 VALUE 0.
05 COST-TOTAL PIC S9(7)V99 VALUE 0.
01 DATE-AND-TIME.
05 CD-YEAR PIC 9999.
05 CD-MONTH PIC 99.
40. DATA DIVISION
• Describe data that exists in another program,
or storage you want to associate with a
symbolic name in the LINKAGE SECTION.
LINKAGE SECTION.
01 LK-DATA-AREA
05 NAME PIC X(40).
05 AGE PIC 999.
41. DATA DIVISION
The LOCAL-STORAGE SECTION is used to have
storage allocated each time a program is
entered, and deallocated on return from the
program. Used for compatibility with C or Java.
LOCAL-STORAGE SECTION.
01 CUST-NO PIC X(3).
01 COST PIC 9(5)V99.
42. Initialization of Storage
• WORKING-STORAGE for programs is allocated at
the start of the run unit.
• Any data items with VALUE clauses are
initialized to the appropriate value at that time.
43. Initialization of Storage
• For the duration of the run unit, WORKING-STORAGE
items persist in their last-used state. Exceptions are:
1) A program with INITIAL specified in the PROGRAM-
ID paragraph In this case, WORKING-STORAGE data
items are reinitialized each time the program is entered.
IDENTIFICATION DIVISION.
PROGRAM-ID. MAIN IS INITIAL.
...
44. Initialization of Storage
• For the duration of the run unit, WORKING-STORAGE
items persist in their last-used state. Exceptions are:
2) A subprogram that is dynamically called and then
canceled In this case, WORKING-STORAGE data items
are reinitialized on the first reentry into the program
following the CANCEL.
MOVE ‘PROG23’ TO PROGID
CALL PROGID
CANCEL PROGID
CALL PROGID
45. Group and Data Items
01 Customer-Record.
05 Customer-Name.
10 Last-Name Pic x(17).
10 Filler Pic x.
10 Initials Pic xx.
05 Part-Order.
10 Part-Name Pic x(15).
10 Part-Color Pic x(10).
46. REDEFINES
01 MONTH-NAMES.
05 STRING-1 PIC X(15)
VALUE “JANFEBMARAPRMAY’.
05 MONTH REDEFINES STRING-1
OCCURS 5 TIMES PIC XXX.
MOVE MONTH(3) TO MONTH-OUT
50. Constants
• A constant is a data item that has only one value and it
can never change
• Unfortunately, COBOL does not define a construct
specifically for constants
• Moral: All values are subject to change
Data Division.
01 Report-Header pic x(50)
value "Company Report".
01 Interest pic 9v9999
value 1.0265.
51. Figurative Constants
There are some figurative constants supplied by
the language:
• ZERO - an appropriate form of 0
• SPACE - x’40’
• HIGH-VALUES - binary 1’s
• LOW-VALUES - binary 0’s
• QUOTE - a single quote
• NULL - binary 0’s used for pointers
• ALL - Technically not a figurative
constant: X PIC X(5) VALUE ALL ‘3’.
52. Tables (Arrays)
• A table is a set of logically consecutive data items that
you define in the DATA DIVISION by using the OCCURS
clause.
01 TABLE.
05 TABLE-ENTRY OCCURS 10 TIMES.
10 NUM PIC 99.
10 NAME PIC X(30).
10 ITEM PIC X(5) OCCURS 3 TIMES.
53. Referencing a Table
01 TABLE.
05 TABLE-ENTRY OCCURS 10 TIMES.
10 NUM PIC 99.
10 NAME PIC X(30).
10 ITEM PIC X(5) OCCURS 3 TIMES.
COBOL tables are 1-indexed
Some valid References with subscripts:
TABLE-ENTRY(SUB)
TABLE
NUM(SUB)
NAME(SUB)
ITEM(SUB1,SUB2)
54. Subscripts vs Indexes
• Subscripts are defined separately from the table
definitions.
01 MYTABLE.
05 ITEM PIC X(3) OCCURS 10 TIMES.
01 I PIC 9(4) BINARY.
...
MOVE 1 TO I
MOVE “ABC” TO ITEM(I)
• Subscripts are numeric fields – choose BINARY fields for
efficiency, although packed and zoned fields also work
55. Subscripts vs Indexes
• Subscripts can be easily printed
01 MYTABLE.
05 ITEM PIC X(3) OCCURS 10 TIMES.
01 I PIC 9(4) BINARY.
...
MOVE 1 TO I
MOVE “ABC” TO ITEM(I)
DISPLAY I
56. Subscripts vs Indexes
• Subscripts represent an occurrence number, 1 is
the first occurrence, 2 is the second, …
01 MYTABLE.
05 ITEM PIC X(3) OCCURS 10 TIMES.
01 I PIC 9(4) BINARY.
...
PERFORM VARYING I FROM 1 BY 1 UNTIL I > 10
DISPLAY ITEM(I)
END-PERFORM
58. Subscripts vs Indexes
• Indexes are created when a table is defined
01 MYTABLE.
10 LETTERVALS PIC X(10) VALUE 'ABCDEFGHIJ'.
10 LETTER REDEFINES LETTERVALS
PIC X(1) OCCURS 10 TIMES
INDEXED BY I.
• Indexes are manipulated with SET statements and
automatically altered by PERFORM statements
SET I TO 1
MOVE LETTER(I) TO CHAROUT
59. Subscripts vs Indexes
• Indexes are generally more efficient than subscripts
• Indexes represent offsets from the beginning of the table
SET I TO 1
Causes I to have the binary value 0 internally.
• It takes a bit of work to print them
61. Tables with Two Dimensions
01 TABLE.
05 TABLE-ENTRY OCCURS 10 TIMES
INDEXED BY SUB1.
10 NUM PIC 99.
10 NAME PIC X(30).
10 ITEM PIC X(5) OCCURS 3 TIMES
INDEXED BY SUB2.
Valid References with subscripts:
TABLE-ENTRY(SUB1)
TABLE
NUM(SUB1)
NAME(SUB1)
ITEM(SUB1,SUB2)
62. Subscripts and Indexes
• In a two-dimensional table, the two subscripts
correspond to the row and column numbers.
• In a three-dimensional table, the three
subscripts correspond to the depth, row, and
column numbers.
• Indexes use address computation to efficiently
reference items in a table.
64. PROCEDURE DIVISION
• The PROCEDURE DIVISION is where you code the
executable statements in your COBOL program
• Divided into Paragraphs (terminated with periods):
100-MAIN.
DISPLAY “HELLO…”
PERFORM 200-SUB
GOBACK
.
200-SUB.
DISPLAY “…WORLD!”
.
65. The Evils of Coding Periods
• Periods have proven troublesome in the
procedure division, and a new style of coding
has evolved to deal with them
• The period is a statement terminator but we
want to think of it as a paragraph terminator only
• We will code in a “period-less” style
• Only use periods to end a paragraph name
66. PROCEDURE DIVISION
• To resolve ambiguity caused by not using
periods, we will use statement delimiters:
END-IF
END-PERFORM
END-COMPUTE
...
70. MOVE STATEMENT
• Used to copy data from one field to
another
• Example -
MOVE X-FIELD TO Y-FIELD Z-FIELD
• Data is copied from the sending field to the
receiving field
71. MOVE STATEMENT
• To move data from one field to another field, the two
fields should be “compatible” but don’t have to be
identically pictured
• Alphanumeric - PIC X(10)
• Numeric - PIC 999v99
• Numeric-Edited - PIC 999.99-
Compatible moves:
-Alphanumeric to Alphanumeric
-Numeric to Numeric
-Numeric to Numeric edited
72. MOVE STATEMENT
• Compatible moves:
-Alphanumeric to Numeric if the sending field is an
unsigned integer
-Alphanumeric to Numeric edited if the sending field is an
unsigned integer
-Numeric to Alphanumeric if the sending field is an
unsigned integer
73. MOVE STATEMENT
• Compatible moves:
-Numeric edited fields can be sent to Numeric and
Numeric edited fields – this causes a de-edit process to
occur
-Numeric edited fields can be sent to Alphanumeric and
Alphanumeric edited fields – this causes a de-edit
process to occur
74. MOVE STATEMENT
• Moving data can cause data conversions
to occur.
01 X PIC S9(4) BINARY.
01 Y PIC S9(5) PACKED-DECIMAL.
MOVE X TO Y
75. MOVE STATEMENT
• If the receiving field is larger than the sending
field, the receiving field is filled with leading 0’s
in a numeric move:
01 X PIC S9(3) VALUE 123.
01 Y PIC S9(5) VALUE 0.
MOVE X TO Y
RESULT: Y = X’F0F0F1F2C3’
76. MOVE STATEMENT
• If the receiving field is larger than the sending
field, the receiving field is filled with trailing
spaces in a alphanumeric move.
01 X PIC X(3) VALUE “ABC”.
01 Y PIC X(5) VALUE SPACES.
MOVE X TO Y
RESULT: Y = X’C1C2C34040’
77. MOVE STATEMENT
• If the receiving field is smaller than the sending
field, data will be truncated on the left for
numeric moves and on the right for
alphanumeric moves
01 X PIC S9(5) VALUE 12345.
01 Y PIC S9(3) VALUE 0.
01 A PIC X(5) VALUE ‘ABCDE’
01 B PIC X(3) VALUE SPACES.
MOVE X TO Y
MOVE A TO B
RESULT: Y = X’F3F4F5’
B = X’C1C2C3’
78. Use Move for Assignment
01 WORK.
05 A-FIELD PIC X(3).
05 B-FIELD PIC S999V99.
MOVE “ABC” TO A-FIELD
MOVE 123.45 TO B-FIELD
MOVE LOW-VALUE TO WORK
79. Assignment Can Cause
Conversions
Consider the following move:
01 A PIC S999V99.
01 B PIC ZZ9.99-.
01 C PIC S9(5)V9999 PACKED-DECIMAL.
MOVE A TO B Zoned to Numeric-edited
MOVE A TO C Zoned to Packed-decimal
80. MOVE CORRESPONDING
MOVE CORRESPONDING identifier-1 TO identifier-2
CORR
• Usually a bad idea
• Both identifiers must name group items.
• Elementary items with the same name are moved.
• 01 A-GROUP. 01 B-GROUP.
05 W PIC X(3). 05 W PIC X(3).
05 X PIC X(2). 05 X PIC X(2).
05 Y PIC 999. 05 Y PIC 999.
MOVE CORRESPONDING A-GROUP TO B-GROUP
• W to W, X to X, Y to Y
81. MOVE CORRESPONDING
• Subordinate items must not be identified by the keyword
FILLER
• No reference modification for either identifier
• Subordinate items must not include a REDEFINES,
RENAMES, OCCURS, INDEX or POINTER description
• 01 A-GROUP. 01 B-GROUP.
05 W PIC X(3). 05 P PIC X(3).
05 X PIC X(2). 05 X PIC X(2).
05 Y PIC 999. 05 W PIC 999.
MOVE CORRESPONDING A-GROUP TO B-GROUP
• W to W, X to X
83. INITIALIZE
• SPACE is the implied sending item for
receiving items of category alphabetic,
alphanumeric, alphanumeric-edited,
DBCS, national, or national-edited.
• ZERO is the implied sending item for
receiving items of category numeric or
numeric-edited.
86. ADD Semantics
• All identifiers or literals that precede the keyword
TO are added together, and this sum is added to
and stored in identifier-2. This process is
repeated for each successive occurrence of
identifier-2 in the left-to-right order in which
identifier-2 is specified.
ADD X Y Z TO P Q
Before X=1, Y=2, Z=3, P=4, Q=6
After X=1, Y=2, Z=3, P=10, Q=12
87. ADD EXAMPLES
• ADD X TO Y
• ADD X Y Z TO P
• ADD X Y TO P Q
• ADD 1 TO Z
• ADD X TO Y ROUNDED
• ADD X TO Y
ON SIZE ERROR
DISPLAY “ADD ERROR”
END-ADD
89. ADD…GIVING Semantics
• All identifiers or literals that precede the keyword TO are
added together, and this sum is added to identifier-2 to
obtain a temporary sum. (Identifier-2 is unchanged)
• The the temporary sum is moved to identifier-3.
ADD X Y Z TO V GIVING P
Before X=1, Y=2, Z=3, V=4, P=6
After X=1, Y=2, Z=3, V=4, P=10
91. SUBTRACT
• All identifiers or literals preceding the keyword FROM are
added together and their sum is subtracted from and
stored immediately in identifier-2. This process is
repeated for each successive occurrence of identifier-2,
in the left-to-right order in which identifier-2 is specified.
SUBTRACT X Y FROM P Q
Before: X=1,Y=2, P=3,Q=4
After: X=1,Y=2, P=0,Q=1
93. SUBTRACT Semantics
• All identifiers or literals preceding the keyword FROM are
added together and their sum is subtracted from
identifier-2 to obtain a temporary value which is moved
to identifier-3.
SUBTRACT X Y FROM P GIVING Q
Before: X=1,Y=2,P=5,Q=6
After: X=1,Y=2,P=5,Q=2
95. MULTIPLY Semantics
• In format 1, the value of identifier-1 or literal-1 is
multiplied by the value of identifier-2; the product is then
placed in identifier-2. For each successive occurrence of
identifier-2, the multiplication takes place in the left-to-
right order in which identifier-2 is specified.
MULTIPLY X BY P Q
Before: X=2,P=4,Q=5
After: X=2,P=8,Q=10
97. MULTIPLY
• In format 2, the value of identifier-1 or literal-1 is
multiplied by the value of identifier-2 or literal-2. The
product is then stored in the data items referenced by
identifier-3. Identifier-2 is unchanged.
MULTIPLY X BY Y GIVING Z
Before: X=2, Y=3, Z=4
After: X=2, Y=3, Z=6
99. DIVIDE
• In format 1, the value of identifier-1 or literal-1 is divided
into the value of identifier-2, and the quotient is then
stored in identifier-2. For each successive occurrence of
identifier-2, the division takes place in the left-to-right
order in which identifier-2 is specified.
DIVIDE X INTO Y Z
Before: X=3, Y=7, Z=12
After: X=3, Y=2, Z=4
101. DIVIDE
• In format 2, the value of identifier-1 or literal-1 is divided
into the value of identifier-2 or literal-2. The value of the
quotient is stored in each data item referenced by
identifier-3.
DIVIDE X INTO Y GIVING Z
Before: X = 2, Y = 13, Z = 1
After: X = 2, Y = 13, Z = 6
103. DIVIDE
• In format 3, the value of identifier-1 or literal-1 is
divided by the value of identifier-2 or literal-2.
The value of the quotient is stored in each data
item referenced by identifier-3.
DIVIDE X BY Y GIVING Z
Before: X = 10, Y = 3, Z = 1
After: X = 10, Y = 3, Z = 3
105. DIVIDE
• In format 4, the value of identifier-1 or literal-1 is divided
into identifier-2 or literal-2. The value of the quotient is
stored in identifier-3, and the value of the remainder is
stored in identifier-4.
DIVIDE X INTO Y
GIVING Z
REMAINDER R
Before: X = 2, Y = 9, Z = 8, R = 7
After: X = 2, Y = 9, Z = 4, R = 1
107. COMPUTE
• COMPUTE can be used to initialize a numeric field
• Usually reserved for nontrivial computations. For
simple computations choose ADD, SUBTRACT,
MULTIPLY or DIVIDE
05 X PIC S9(4)V9 PACKED DECIMAL.
COMPUTE X ROUNDED = (A + B) / 2.3
ON SIZE ERROR
DISPLAY “X WAS TRUNCATED”
END-COMPUTE
110. Move Mode I/O
Input Buffers Output Buffers
READ MYFILE INTO
MYREC
…
WRITE RECOUT
FROM MYREC
Region
01 MYREC PIC X(80).
111. QSAM FILE OPERATIONS
ENVIRONMENT DIVISION.
INPUT-OUTPUT-SECTION.
FILE-CONTROL.
SELECT MY-INPUT-FILE
ASSIGN TO MASTER
FILE STATUS IS MAST-STAT.
• MY-INPUT-FILE – Internal file name
• MASTER – External DD name
• MAST-STAT – A two byte PIC XX field in which the
operating system returns a status code. Consult IBM
Language Reference page 315 for status code details.
112. QSAM FILE OPERATIONS
ENVIRONMENT DIVISION.
INPUT-OUTPUT-SECTION.
FILE-CONTROL.
SELECT MY-INPUT-FILE
ASSIGN TO MASTER
FILE STATUS IS MAST-STAT.
DATA DIVISION.
FILE SECTION.
FD MY-INPUT-FILE
01 RECORD-AREA PIC X(80).
113. QSAM
• Queued Sequential Access Method
• For input files, records are buffered when the file
is OPENed
• For output, records are buffered before being
written
• Records are processed from the beginning
record sequentially to the end of the file
• Very efficient access method for sequential files
• Sometimes referred to as “flat” files
114. QSAM FILE OPERATIONS
• Every file must be OPENed before it can
be processed.
• Opening a QSAM Input file queues
records for subsequent read operations
• OPEN INPUT MY-INPUT-FILE
• OPEN OUTPUT MY-OUTPUT-FILE
• Files should be closed when you have
finished processing the records
• CLOSE MY-FILE
118. QSAM Input File Operations
• Remember: READ a file, WRITE a record.
READ MY-INPUT-FILE
AT END MOVE ‘NO’ TO MORE-RECS
END-READ
• This is a locate-mode read and the most
efficient way to read records
119. File Reading
READ MY-INPUT-FILE INTO MY-REC
AT END MOVE ‘NO’ TO MORE-RECS
END-READ WRITE
• This is a move-mode read and the least
efficient way to deliver records
120. QSAM Output File Operations
• Write a record!
• WRITE MY-RECORD (locate mode)
• WRITE MY-RECORD FROM REC-BUFF
END-WRITE (move mode)
• CLOSE MY-OUTPUT-FILE
• CLOSE MY-INPUT-FILE
121. Sequential File Reading Pattern
READ MYFILE
AT END MOVE ‘N’ TO MORE-RECS
END-READ
PERFORM UNTIL MORE-RECS = ‘N’
(process a record code)
READ MYFILE
AT END MOVE ‘N’ TO MORE-RECS
END-READ
END-PERFORM
PRIMING READ
CONTINUATION
READ
122. File Status Codes
• 00 – normal
• 10 – end of file
• 2x – invalid key
• 3x – permanent i/o error
• 4x – logic error
• 9x – unsuccessful operation
123. Exercise #1
• Create a file of 80 byte records
• Each record has 3 fields
• AFIELD – ZONED DECIMAL
with 4 DIGITS & 2 DECIMALS
• BFIELD – PACKED DECIMAL
with 7 DIGITS & 3 DECIMALS
• CFIELD - PACKED DECIMAL
with 7 DIGITS & 1 DECIMAL
• Print a report with a column for each field and a column for the
computed value :
(AFIELD + BFIELD)/ CFIELD
Print the result with 2 decimals rounded.
Total each column.
124. FLOW OF CONTROL
• There is a theoretical result in Computer Science by two
Italian mathematicians, Boehm and Jacopini, that states
that only 3 control structures are required to write any
program:
• Sequence - Do this, now do this, now do this, …
• Selection - If something is true do this, else do that
• Repetition – While something is true, do this
• Practice has shown that being able to create procedures
is helpful in overcoming complexity, but they aren’t
strictly necessary
• One implication of this result is that GO TO statements
aren’t needed
127. IF
• The condition is tested and either the true
or false blocks are selected for execution
• Don’t use NEXT SENTENCE if you are
using END-IF as the delimiter (and you
should). Use of NEXT SENTENCE causes
execution to continue with the next closest
period, which is probably the end of the
paragraph.
128. IF Examples
IF X < Y
ADD 1 TO X
DISPLAY “AAA”
ELSE
DISPLAY “BBB”
END-IF
IF X > Y
DISPLAY “X WAS BIGGER”
END-IF
129. NESTED IFs
• Each ELSE is matched with the nearest preceding IF
IF X < Y
DISPLAY “XXX”
IF Y < Z
DISPLAY “ZZZ”
ELSE
DISPLAY “AAA”
END-IF
• MORAL: Indent properly and terminate all if statements
with END-IF
131. EVALUATE
EVALUATE PLANET-NUMBER
WHEN 1 MOVE "Mercury" TO PLANET-NAME
WHEN 2 MOVE "Venus " TO PLANET-NAME
WHEN 3 MOVE "Earth " TO PLANET-NAME
WHEN 4 MOVE "Mars " TO PLANET-NAME
WHEN 5 MOVE "Jupiter" TO PLANET-NAME
WHEN 6 MOVE "Saturn " TO PLANET-NAME
WHEN 7 MOVE "Uranus " TO PLANET-NAME
WHEN 8 MOVE "Neptune" TO PLANET-NAME
WHEN 9 MOVE "Pluto " TO PLANET-NAME
WHEN OTHER MOVE " " TO PLANET-NAME
END-EVALUATE.
132. EVALUATE
EVALUATE PLANET-NAME
WHEN "Mercury" MOVE 1 TO PLANET-NUMBER
WHEN "Venus " MOVE 2 TO PLANET-NUMBER
WHEN "Earth " MOVE 3 TO PLANET-NUMBER
WHEN "Mars " MOVE 4 TO PLANET-NUMBER
WHEN "Jupiter" MOVE 5 TO PLANET-NUMBER
WHEN "Saturn " MOVE 6 TO PLANET-NUMBER
WHEN "Uranus " MOVE 7 TO PLANET-NUMBER
WHEN "Neptune" MOVE 8 TO PLANET-NUMBER
WHEN "Pluto " MOVE 9 TO PLANET-NUMBER
WHEN OTHER MOVE 0 TO PLANET-NUMBER
END-EVALUATE.
133. EVALUATE
EVALUATE TRUE
WHEN PLANET-NAME = "Mercury" MOVE 1 TO PLANET-NUMBER
WHEN PLANET-NAME = "Venus " MOVE 2 TO PLANET-NUMBER
WHEN PLANET-NAME = "Earth " MOVE 3 TO PLANET-NUMBER
WHEN PLANET-NAME = "Mars " MOVE 4 TO PLANET-NUMBER
WHEN PLANET-NAME = "Jupiter" MOVE 5 TO PLANET-NUMBER
WHEN PLANET-NAME = "Saturn " MOVE 6 TO PLANET-NUMBER
WHEN PLANET-NAME = "Uranus " MOVE 7 TO PLANET-NUMBER
WHEN PLANET-NAME = "Neptune" MOVE 8 TO PLANET-NUMBER
WHEN PLANET-NAME = "Pluto " MOVE 9 TO PLANET-NUMBER
WHEN OTHER MOVE 0 TO PLANET-NUMBER
END-EVALUATE.
134. EVALUATE
EVALUATE Qty ALSO TRUE ALSO Member
WHEN 1 THRU 5 ALSO VOP < 501 ALSO "Y"
MOVE 2 TO Discount
WHEN 6 THRU 16 ALSO VOP < 501 ALSO "Y"
MOVE 3 TO Discount
WHEN 17 THRU 99 ALSO VOP < 501 ALSO "Y"
MOVE 5 TO Discount
WHEN 1 THRU 5 ALSO VOP < 2001 ALSO "Y"
MOVE 7 TO Discount
WHEN 6 THRU 16 ALSO VOP < 2001 ALSO "Y"
MOVE 12 TO Discount
WHEN 17 THRU 99 ALSO VOP < 2001 ALSO "Y"
MOVE 18 TO Discount
WHEN 1 THRU 5 ALSO VOP > 2000 ALSO "Y"
MOVE 10 TO Discount
WHEN 6 THRU 16 ALSO VOP > 2000 ALSO "Y"
MOVE 23 TO Discount
END-EVALUATE
135. EVALUATE
EVALUATE TRUE ALSO Position
WHEN L-Arrow ALSO 2 THRU 10
SUBTRACT 1 FROM Position
WHEN R-Arrow ALSO 1 THRU 9
ADD 1 TO Position
WHEN L-Arrow ALSO 1
MOVE 10 TO Position
WHEN R-Arrow ALSO 10
MOVE 1 TO Position
WHEN DelKey ALSO ANY
PERFORM DeleteChar
WHEN Char ALSO 1 THRU 9
PERFORM InsertChar
ADD 1 TO Position
WHEN Char ALSO 10
PERFORM InsertChar
WHEN OTHER PERFORM
DisplayErrorMessage
END-EVALUATE
137. PERFORM Paragraph
• PERFORM paragraph name
– Execute all instructions in the paragraph
– Return control to the next instruction after the PERFORM
PERFORM 100-ROUTINE
PERFORM 200-ROUTINE
PERFORM 100-ROUTINE
…
100-ROUTINE.
…
200-ROUTINE.
…
300-ROUTINE.
138. PERFORM THRU
• PERFORM paragraph name THRU paragraph name
PERFORM 100-XXX THUR 100-XXX-EXIT
100-XXX.
DISPLAY ‘IN 100-XXX’.
100-XXX-EXIT.
EXIT.
• There is an implicit EXIT in every paragraph so why do I need to code it explicitly?
139. Perform Thru (Let it Die)
• I view use of PERFORM…THRU as an older,
unnecessary style, caused by a compiler problem that
existed many years ago. Using PERFORM THRU was a
way to address this ancient problem. The problem has
been fixed for many years now, yet old habits die hard.
143. PERFORM UNTIL
• MOVE 0 TO X
PERFORM UNTIL X > 10
MOVE X TO X-EDITED
DISPLAY X-EDITED
ADD 1 TO X
END-PERFORM
• PERFORM X-PARA UNTIL X > 10
• PERFORM X-PARA WITH TEST AFTER
UNTIL X > 10
149. Inline PERFORM
MOVE ZERO TO Y
PERFORM UNTIL X = 0
READ… AT END MOVE 0 TO X
ADD X TO Y
DISPLAY Y
END-PERFORM
150. Alternate PERFORM
PERFORM 100-PARA VARYING I FROM 1 BY 1 UNTIL I > 5
AFTER J FROM 1 BY 1 UNTIL J > 3
END-PERFORM
100-PARA.
DISPLAY I J
.
1 1
1 2
1 3
2 1
2 2
2 3
3 1
3 2
3 3
4 1 …
151. Table Processing with Subscripts
01 TOT PIC S9(8) PACKED DECIMAL.
01 SUB1 PIC 99.
01 TEMP-REC.
05 TEMP OCCURS 12 TIMES
PIC S9(4).
…
MOVE 0 TO TOT
PERFORM VARYING SUB1 FROM 1 BY 1
UNTIL SUB1 > 12
ADD TEMP(SUB1) TO TOT
ENDPERFORM
152. Table Processing with Indexes
01 TOT PIC S9(8) PACKED DECIMAL.
01 TEMP-REC.
05 TEMP OCCURS 12 TIMES INDEXED BY K
PIC S9(4).
…
MOVE 0 TO TOT
PERFORM VARYING K FROM 1 BY 1
UNTIL K > 12
ADD TEMP(K) TO TOT
END-PERFORM
153. Manipulating Indexes
• Indexes can’t be manipulated with ordinary
arithmetic commands. Instead use SET.
• SET K TO 3
• SET K UP BY 1
• SET K UP BY 2
• SET K DOWN BY 3
155. EXIT
• Sometimes used to provide an explicit exit from a
paragraph or a program.
• There is an implicit exit at the end of each paragraph
• 100-PARA.
DISPLAY X
EXIT
.
156. STOP
• Usually used to permanently halt execution of a
program
• Can be used to temporarily halt execution and
require operator intervention
157. GOBACK
• Functions like an EXIT PROGRAM when coded
at the end of a called program
• Functions like STOP RUN when coded in a main
program
• I prefer coding this in place of STOP RUN
158. GO TO
• Causes an unconditional jump in program execution to the
procedure that is named.
• This statement should be used only in very special situations, for
instance, to branch to an error routine that terminates the program
from a deeply nested area of your program.
• Overuse (any?) of this statement is unnecessary and leads to
spaghetti code
• Don’t even think of using the alternate forms of GO TO !
159. Exercise #2
• Create a file of 80 byte records
• Each record has 3 fields
• CUSTLNAME – CHARACTER 15
• CUSTFNAME - CHARACTER 15
• BALANCE - PACKED DECIMAL – 5 BYTES 2 DECS
• Create a table of the file data using subscripts.
• Sort the table with a bubble sort on customer name.
• Print the sorted table:
Last Name First Name Balance
162. SEARCH
• Search performs a sequential search with an index
• Rule of thumb: Use SEARCH for tables with 20 items or less
• DEPENDING ON field must contain the number of table entries
01 RECCOUNT PIC 9(2).
01 SALES-TAX.
05 TAB-ENTRIES OCCURS 20 TIMES
DEPENDING ON RECCOUNT
INDEXED BY K.
10 ZIPCODE PIC 9(5).
10 RATE PIC V999.
SET K TO 1
SEARCH TAB-ENTRIES
AT END MOVE 0 TO TAX
WHEN ZIPIN = ZIPCODE(K)
COMPUTE TAX = RATE(K) * AMOUNT
END-SEARCH
163. Exercise #4
• Read the file from exercise #3
• Store the data in a table
• Read the file BCST.SICCC01.PDSLIB(DAT4EXER).
Each record has a LAST NAME, FIRST NAME field:
Last name – columns 1 – 15
First name – columns 16 – 30
• Code a Sequential Search statement to find each name
in the file. Print each name, “Found” or “Not Found”, and
the customer balance if found.
165. SEARCH ALL
• SEARCH ALL performs a binary search with an index
• ENTRIES MUST BE IN ORDER BY KEY!
• No SET necessary (the whole table is searched)
• RECCOUNT must contain the number of table entries.
01 RECCOUNT PIC 999 PACKED-DECIMAL.
01 SALES-TAX.
05 TAB-ENTRIES OCCURS 100 TIMES
DEPENDING ON RECCOUNT
ASCENDING KEY ZIPCODE
INDEXED BY K.
10 ZIPCODE PIC 9(5).
10 RATE PIC V999.
SEARCH ALL TAB-ENTRIES
AT END MOVE 0 TO TAX
WHEN ZIPCODE(K) = ZIPIN
COMPUTE TAX = RATE(K) * AMOUNT
END-SEARCH
166. SEARCH ALL CONSTRAINTS
• The condition following WHEN must test for equality
• Compound conditions with ANDs not ORs
• Only one WHEN clause
• VARYING not allowed
• OCCURS item and its index must appear on the left of the
equal sign
– WHEN TEMP(K) = 80
167. SEARCH ALL Constraints
• Table must indicate ASCENDING or
DESCENDING KEY
01 TABLE.
05 CUST-REC OCCURS 40 TIMES
DEPENDING ON RECCOUNT
ASCENDING KEY CUST
INDEXED BY K.
10 CUST PIC 9(4).
10 RATE PIC V999.
168. Exercise #5
• Read the file from exercise #3
• Store the data in a table
• Read the file BCST.SICCC01.PDSLIB(DAT4EXER).
Each record has a LAST NAME , FIRST NAME fields
Last name – columns 1 – 15
First name – columns 16 – 30
• Code a binary search statement to find each name in the
file. Print each name, “Found” or “Not Found”, and the
customer balance if found.
170. STRING
• Used to build string expressions by
concatenation (blanks not stored)
STRING FNAME DELIMITED BY “ “
MNAME DELIMITED BY “ “
LNAME DELIMITED BY “ “
INTO NAME-OUT
171. STRING
• Blanks stored
• DELIMITED BY SIZE means include the entire literal
or variable contents
STRING FNAME DELIMITED BY “ “
“ “ DELIMITED BY SIZE
MNAME DELIMITED BY “ “
“ “ DELIMITED BY SIZE
LNAME DELIMITED BY “ “
“ “ DELIMITED BY SIZE
INTO NAME-OUT
174. UNSTRING
• Separates a string into several component
strings
• Sending field must be alphanumeric
UNSTRING NAME
DELIMITED BY “,”
INTO LNAME
FNAME
MI
END-UNSTRING
179. Static and Dynamic Call
• Programs A and B that are linked together
prior to being loaded are statically linked.
If A calls B, the call is static
• If programs A and B are separately
compiled and linked, A can call B
dynamically:
01 PGMNAME PIC X(8) VALUE ‘B’.
…
CALL PGMNAME
180. Calling Other Programs Statically
CALL literal program name
USING identifier-1, …
Examples
CALL ‘CUST1030’ USING X,Y
CALL ‘PROG1000’
181. CALLING ANOTHER PROGRAM
CALL ‘PROGXXXX’ USING A,B
IDENTIFICATION DIVISION.
PROGRAM-ID. PROGXXXX.
…
LINKAGE SECTION.
01 X PIC X(5).
01 Y PIC 999V99.
PROCEDURE DIVISION USING X,Y.
…
GOBACK
.
182. Static and Dynamic CALLS
• Two methods for generating dynamic
calls
1. CALL MYPROG USING X,Y,Z
(Using an identifier insures a dynamic
call.)
2. DYNAM/NODYNAM compiler option
determines whether a static or dynamic
call occurs
3. At TSYS all calls are dynamic.
183. Exercise #8
• Write a main program that,
1) Prints “I am in the main program”,
2) Calls your subprogram,
3) Prints “I am back in the main program”
• Write a subprogram that prints “I am in the
subprogram.
• Compile and link the programs, execute
the main program
184. Exercise #9
• Write a main program that passes 3
packed decimal numbers to a subprogram
and a fourth variable in which to receive a
result.
• Write a subprogram that accepts the 3
integers, computes their sum and returns
the answer to the main
• Have the main print the result
185. Exercise #10
• Write a main program that passes a
variable X by reference and Y by content
• Have the subprogram add one to both
numbers
• Have the main program print X and Y after
returning from the subprogram
186. NUMERIC Class Test
• Before using a “suspect” field that has a PIC of
9’s, use the NUMERIC class test to verify the
field before doing arithmetic
IF AMOUNT-IN IS NUMERIC
ADD 1 TO AMOUNT-IN
ELSE
DISPLAY “AMOUNT IS NOT NUMERIC”
END-IF
187. Sign Test
• Numeric data can be tested for positive, negative, and
zero values
IF AMOUNT-IN IS POSITIVE
ADD 1 TO AMOUNT-IN
END-IF
IF AMOUNT-IN IS NEGATIVE
DISPLAY AMOUNT-IN
END-IF
IF AMOUNT-IN IS ZERO
DISPLAY “THE FIELD IS ZERO”
END-IF
189. INSPECT (TALLYING)
INSPECT MYLINE
TALLYING ECOUNT FOR ALL “E“
AFTER INITIAL “START"
BEFORE INITIAL “END“
END-INSPECT
INSPECT WORK TALLYING
COUNT1 FOR LEADING “*”
COUNT2 FOR CHARACTERS
END-INSPECT
INSPECT WORK TALLYING
COUNT1 FOR ALL “*” BEFORE “.”
COUNT2 FOR ALL CHARACTERS AFTER “.”
END-INSPECT
191. INSPECT (REPLACING)
INSPECT MYDATA REPLACING ALL “X" BY “Y“
AFTER INITIAL “A"
BEFORE INITIAL “Z“
INSPECT MYDATA REPLACING LEADING “ " BY “+“
INSPECT MYDATA REPLACING ALL “A" BY “+“
AFTER INITIAL “X"
INSPECT MYDATA REPLACING FIRST “A" BY “+"
AFTER INITIAL “A"
BEFORE INITIAL “Z“
INSPECT MYDATA REPLACING ALL “AAAA" BY “ZZZZ"
193. INSPECT (CONVERTING)
INSPECT TEXTLINE CONVERTING
"abcdefghijklmnopqrstuvwxyz" TO
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
INSPECT FIELDA CONVERTING
“1234567890” TO “ABCDEFGHIJ”
194. REFERENCE MODIFICATION
• Allows you to process PIC 9 and PIC X fields
as if they were an array of characters.
• FIELDNAME(start pos : [ length])
05 FIELDA PIC X(7) VALUE ‘ABCDEFG’.
FIELDA(1:3) “ABC”
FIELDA(2:2) “BC”
FIELDA(4: ) “DEFG”
195. Qualification of Names
• COBOL allows the same variable name to be used to
define fields in different records or group items.
• Duplicate names must be qualified when they are
referenced
01 XFIELD.
05 YFIELD.
10 ZFIELD PIC X(3).
If ZFIELD is a duplicate name it can be qualified in two
ways: ZFIELD OF YFIELD
ZFIELD OF XFIELD
196. Intrinsic Functions
• COBOL does not permit user-defined
functions or procedures
• Intrinsic (built-in) Functions can be used in
your programs
• Three broad categories of intrinsic
functions: date functions, numeric
functions and string functions.
197. Intrinsic Functions
• Intrinsic Function values are replaced in the position
where they occur by the function result.
• In COBOL, an Intrinsic Function is a temporary data item
whose value is determined at the time the function is
executed.
• Functions that return a number value (numeric & integer)
are always considered to be signed.
• A function that returns a number value can be used only
in an arithmetic expression or as the source of a MOVE
statement.
198. Intrinsic Functions
• Intrinsic function pattern:
FUNCTION FunctionName(Parameters)
• FunctionName is the name of the function and
Parameters is one or more parameters supplied
to the function.
COMPUTE NUM = FUNCTION RANDOM(99)
MOVE FUNCTION REVERSE(“ABCD”) TO NAME
199. Sample Intrinsic Functions
• CHAR(PosInt) AlphanumericReturns the character at
ordinal position PosInt of the collating sequence.
• ORD(Alph) IntegerReturns the ordinal position of
character Alph.
• ORD-MAX({Any}...)
IntegerReturns the ordinal position of whichever of the
parameters has the highest value. All parameters must
be of the same type. The parameter list may be replaced
by an array.
• ORD-MIN({Any}...) IntegerReturns the ordinal
position of whichever of the parameters has the lowest
value. All parameters must be of the same type.
200. Intrinsic Functions
• REVERSE(Alph) Alphanumeric Returns a
character string with the characters in Alph
reversed.
• LOWER-CASE(Alph) Alphanumeric Returns a
character string with the characters in Alph
changed to their lower case equivalents.
• UPPER-CASE(Alph) Alphanumeric Returns a
character string with the characters in Alph
changed to their upper case equivalents
201. Date Intrinsic Functions
• CURRENT-DATE - Returns a 21 character
string representing the current date and
time
• DATE-OF-INTEGER(PosInt) - Returns
the yyyymmdd (standard date) equivalent
of the integer date - PosInt. The integer
date is the number of days that have
passed since Dec 31st 1600 in the
Gregorian Calendar.
202. Math Intrinsic Functions
• MAX({Any}...)Return type on type of Any.
Takes a parameter list and returns the content of
whichever parameter contains the maximum
value.
• The returned type depends upon the parameter
types as follows;
Alphanumeric if parameters are Alphabetic or
Alphnumeric.
Integer if all are integer.
Numeric if all are Numeric.
An array may be used instead of the parameter
list.
203. Math Intrinsic Functions
• SQRT(Num) Returns an approximation of
the square root of Num.
• STANDARD-DEVIATION({Num}...)
Returns an approximation of the standard
deviation of its parameters.
• And many others…
204. Condition Names
01 NO-OF-NEIGHBORS PIC 9.
88 JUST-RIGHT VALUE 2 THRU 3.
88 TOO-FEW VALUE 0 THRU 1.
88 TOO-MANY VALUE 4 THRU 8.
01 MARITAL-STATUS PIC X.
88 VALID-STATUS
VALUE ‘S’ ‘M’ ‘D’ ‘W’.
205. Variable Length Tables
01 TCOUNT PIC S9(3) PACKED-DECIMAL.
01 STATE-TABLE.
05 ST-GROUP OCCURS 1 TO 100 TIMES
DEPENDING ON TCOUNT
ASCENDING KEY IS ZIP
INDEXED BY NDX.
10 ZIP PIC X(5).
10 RATE PIC V9999.
206. Loading a Variable Length Table
PERFORM WITH TEST AFTER
VARYING NDX FROM 1 BY 1
UNTIL PTABLE-EOF OR
NDX = 100
PERFORM FILE-READ
IF NOT PTABLE-EOF
MOVE ZIP-IN TO ZIP(NDX)
MOVE RATE-IN TO RATE(NDX)
ELSE
SET NDX DOWN BY 1
SET TCOUNT TO NDX
END-IF
END-PERFORM
207. Exercise #11
• Read the file BCST.SICCC01.PDSLIB(STATES)
• Store the data in a variable length table
• Read the file BCST.SICCC01.PDSLIB(COBDATA4). Each record has a 2 digit
state code and a 5 byte zip code. For each record in this file print a record on a
report. The report will have the following format:
GA 31907 GEORGIA - VALID ZIP AND STATE
CA 90003 CALIFORNIA - INVALID ZIP
ZD 30002 INVALID STATE
• Capitalize the state name found in the table. Print message next to each
state name separated by a dash.
• Use the SEARCH command perform a sequential search of the table for each look
up. After the program is working, modify it to perform a binary search with SEARCH
ALL
209. Multiple O1 File Descriptions
• Any number of 01 record descriptions can be
coded with the FD
• Only one buffer is used no matter how many
record descriptions have been coded
• Record fields can’t be referenced before the file
is opened or after it is closed
• With multiple record formats, there needs to be a
fixed field to indicate the record type
• Value clauses are only used for 88 level items
211. Variable Length Records
• The RECORD IS VARYING IN SIZE clause
specifies a file containing variable length
records.
212. Variable Length Records
• The RECSIZE number in the DEPENDING
ON phase must be an elementary
unsigned integer data-item declared in the
WORKING-STORAGE SECTION.
FD TRANFILE
RECORD IS VARYING IN SIZE
FROM 1 TO 80 CHARACTERS
DEPENDING ON RECSIZE.
213. Variable Length Record Processing
• When writing a variable length record, the size of
the record must be placed in the RECSIZE
variable before the WRITE is issued.
• When reading a variable length record, the
length of the record is delivered into the
RECSIZE variable.
• The 01 Record description must be long enough
to accommodate the largest record
214. Variable length Record Processing
FD TRANFILE
RECORD IS VARYING IN SIZE
FROM 1 TO 80 CHARACTERS
DEPENDING ON RECSIZE.
01 TRANREC PIC X(80).
88 END-OF-RECS VALUE HIGH-VALUES.
WORKING-STORAGE SECTION.
01 RECSIZE PIC 99.
READ TRANFILE AT END …
DISPLAY TRANREC(1:RECSIZE)
215. Writing Variable Length Records
• Many variable length records have a fixed front end, and
varying numbers of segments
FD CUST
RECORD IS VARYING IN SIZE
FROM 28 TO 408 CHARACTERS
DEPENDING ON RECORD-LEN.
01 CUST-REC.
05 ROOT-SEG.
10 CUST-NO PIC X(6).
10 INVOICE-COUNT PIC S99.
05 INVOICE-SEGMENT OCCURS 20 TIMES INDEXED BY NDX
10 INVOICE-DATE PIC X(8).
10 INVOICE-NO PIC X(5).
10 INVOICE-AMT pIC S9(5)V99.
• You must set the RECORD-LEN before writing the record!
216. Alternative
FD CUSTFILE
RECORD CONTAINS 20 TO 80 CHARACTERS
01 REC.
05 FIXED-PART PIC X(20).
10 …
05 VARY-PART OCCURS 1 TO 6 TIMES
DEPENDING ON COUNT
INDEXED BY NDX
COUNT has to be initialized at the time of writing the record
217. Reading Variable Length Records
FD CUST
RECORD IS VARYING IN SIZE
FROM 28 TO 408 CHARACTERS.
01 CUST-REC.
05 ROOT-SEG.
10 CUST-NO PIC X(6).
10 INVOICE-COUNT PIC S99.
05 INVOICE-SEGMENT OCCURS 20 TIMES INDEXED BY NDX
10 INVOICE-DATE PIC X(8).
10 INVOICE-NO PIC X(5).
10 INVOICE-AMT PIC S9(5)V99.
…
PERFORM VARYING NDX FROM 1 BY 1
UNTIL NDX > INVOICE-COUNT
ADD INVOICE-AMT(NDX) TO AMT-OWED
END-PERFORM
218. EXERCISE #12
• Each A record for a given customer is
followed by one to five B records for that
customer.
• For each A record, write out one variable
length record that contains the A record as
the fixed part and the associated B
records as the variable parts
219. EXERCISE #13
BCST.SICCC01.PDSLIB(COBDATA5) CONTAINS TWO
TYPES OF 80 BYTE RECORDS :
RECORD TYPE “A”
1 BYTE TYPE CODE PIC X CONTAINING “A”
5 BYTE CUSTOMER ID PIC X(5)
RECORD TYPE “B”
1 BYTE TYPE CODE PIC X CONTAINING “B”
5 BYTE PART NUMBER PIC X(5)
6 BYTE COST PIC 9(4)V99
220. EXERCISE #14
Read the variable length records you created in exercise
#5. Produce a report similar to the one below:
CUSTOMER ID PART # COST
10030 22322 1,333.34
23444 3.44
50043 98.77
TOTAL 1435.55
20030 22322 1,333.34
23444 3.44
50043 98.77
TOTAL 1435.55
… …
222. VSAM File Types
• ESDS – Entry Sequenced Data Set
– Allows sequential processing
• RRDS – Relative Record Data Set
– Allows sequential or random access by
relative record number
• KSDS – Key-Sequenced Data Set
– Allows sequential, skip sequential, and
random processing by key
223. VSAM
• VSAM data sets are known as Clusters
• For ESDS or RRDS the cluster consists of
a data component
• For KSDS the cluster consists of a data
component and an index component
• VSAM data is stored on DASD in control
intervals which are grouped into control
areas
224. VSAM
• The Control Interval (CI) is the unit of data
that transfers between the disk and virtual
storage
• CI sizes are multiples of 2K with 4k being
common
• CI’s can be constructed with free space to
accommodate additions to the file
• Control Areas (CA) can be constructed
with free space to accommodate additions
225. VSAM
• VSAM dynamically manages the file by
maintaining information in each CI and CA
• When a CI becomes too “full” the data it
contains is split into two CI’s
• When a CA becomes too “full” the data it
contains is split into two CA’s
• VSAM tries to keep records that are
logically close together, physically close as
well
229. VSAM JCL
• Unlike QSAM files, VSAM files are usually
allocated in a separate job step before
data can be written to the file
• A VSAM cluster is usually created by
deleting and then defining the cluster
• After the cluster is defined, a job can run
which writes data to the file
230. VSAM JCL
• Parameters:
– INDEXED –KSDS
– NONINDEXED – ESDS
– NUMBERED – RRDS
– KEYS ( len off) – primary key info
– CISZ (size) – control interval size
– FREESPACE (ci ca) – free space %’s
234. Creating a VSAM File
• 000100 IDENTIFICATION DIVISION.
• 000200 PROGRAM-ID. VSAM1.
• 000300 ENVIRONMENT DIVISION.
• 000400 INPUT-OUTPUT SECTION.
• 000500 FILE-CONTROL.
• 000600 SELECT PAYROLL-MASTER-OUT ASSIGN TO PAYMASTO
• 000610 ORGANIZATION IS INDEXED
• 000620 ACCESS IS SEQUENTIAL
• 000630 RECORD KEY IS ID-OUT
• 000640 FILE STATUS IS PM-STATUS.
• 000700 SELECT PAYROLL-MASTER-IN ASSIGN TO PAYMASTI.
235. Creating a VSAM File
• 004410 01 PM-STATUS.
• 004430 05 PM-STAT1 PIC X.
• 004440 05 PM-STAT2 PIC X.
• 004441 PROCEDURE DIVISION.
• 004450 OPEN INPUT PAYROLL-MASTER-IN
• 004460 OPEN OUTPUT PAYROLL-MASTER-OUT
• 004461 IF PM-STATUS NOT = '00'
• 004462 PERFORM 300-PRINT-STATUS
• 004463 END-IF
• 004470 PERFORM UNTIL ARE-THERE-MORE-RECORDS = 'NO '
• 004480 READ PAYROLL-MASTER-IN
• 004490 AT END
• 004500 MOVE 'NO ' TO ARE-THERE-MORE-RECORDS
• 004600 NOT AT END
• 004700 PERFORM 200-READ-MODULE
• 004800 END-READ
• 004900 END-PERFORM
• 005000 CLOSE PAYROLL-MASTER-IN
• 005100 PAYROLL-MASTER-OUT
• 005110 GOBACK
236. Creating a VSAM File
• 005130 200-READ-MODULE.
• 005410 MOVE ID-IN TO ID-OUT
• 005420 MOVE NAME-IN TO NAME-OUT
• 005430 MOVE HOURS-IN TO HOURS-OUT
• 005440 MOVE RATE-IN TO RATE-OUT
• 005500 WRITE MASTER-REC-OUT
• 005510 IF PM-STATUS NOT = '00'
• 005520 PERFORM 300-PRINT-STATUS
• 005530 END-IF
• 005600 .
• 005700 300-PRINT-STATUS.
• 005800 DISPLAY 'FILE STATUS CODE:' PM-STATUS
• 005900 GOBACK
• 006000 .
237. VSAM Error Strategy
• VSAM returns a status code after each
operation
• It is imperative that you check each status
code after each operation to insure that
the program is proceeding normally
• The status code is a two byte field
238. OPEN
• OPEN INPUT file-name …
• OPEN OUTPUT file-name …
• OPEN I-O file-name …
• OPEN EXTEND file-name …
For EXTEND, access mode must be
sequential
239. Reading for Sequential Access
READ file-name [NEXT] [RECORD]
[INTO data-name]
[AT END imperative stmt]
[NOT AT END imperative stmt]
[END-READ]
Specify NEXT if access is DYNAMIC and you want
sequential processing
Can be omitted when access is SEQUENTIAL
INTO provides move mode I/O
Omitting INTO provides locate mode I/O
240. Reading for Random Access
READ file-name [RECORD]
[INTO data-name]
[INVALID KEY imperative stmt]
[NOT INVALID KEY imperative
stmt]
[END-READ]
Be sure to set the key of the record you wish
to read beforehand
242. KSDS FILE CREATION
SELECT INVMAST
ASSIGN TO INVMAST
ORGANIZATION IS INDEXED
ACCESS IS SEQUENTIAL
RECORD KEY IS ITEM-NO
FILE STATUS IS FILE-STAT.
FD INVMAST
01 RECORD-AREA.
05 ITEM-NO PIC X(5)
05 PIC X(75).
WORKING-STORAGE SECTION
01 FILE-STAT PIC X(2).
243. KSDS File Commands
OPEN INPUT file-name
OPEN OUTPUT file-name
READ file-name [NEXT] RECORD
[INTO data-area]
[AT END imperative]
[NOT AT END imperative]
[END-READ]
244. KSDS File Commands
WRITE record [FROM]] data-name]
[INVALID KEY imperative]
[NOT INVALID KEY imperative]
[END-WRITE]
REWRITE record [FROM]] data-name]
[INVALID KEY imperative]
[NOT INVALID KEY imperative]
[END-REWRITE]
CLOSE file-name
247. Exercise #15
• Read BCST.SICCC01.PDSLIB(COBDATA6)
• COL 1-5 KEY
• COL 6-25 NAME
• Allocate a KSDS with record size 25 and a key
field in cols 1-5
• Write out a KSDS record for each record in the
file. Write out the records sequentially.
248. Exercise #16
• Read
BCST.SICCC01.PDSLIB(COBDATA7)
• COL 1-5 KEY
• Read a KSDS record (randomly) for each
record in the file. Write out the names you
find sequentially. If the record doesn’t
exist, print a message “Not Found”
249. Nested Programs
• COBOL programs can be nested. There are many
advantages for doing this:
1) The monolithic working storage of most COBOL
programs leads to difficulty in debugging because all
data is global
2) Nested programs break the working storage into
smaller areas that can only be accessed by programs
that need access.
3) Nested programs provide for parameter passing by
techniques found in all modern languages (by value,
by reference)
4) There is no execution degradation because of nested
programs. In fact, calling a nested program is more
efficient than calling a separately compiled program.
250. Nested Programs
• Calling a nested program is as efficient as
performing a paragraph
• Nested programs provide design flexibility and
encourage good program design
• A nested program would be called a function or
subroutine in any other language
• Nested programs unleash the power of COBOL
pointers and allow COBOL programmers to
design data structures that encourage efficient
programming techniques
252. COBOL Pointers
05 PTR1 USAGE IS POINTER.
05 PTR2-P USAGE IS POINTER VALUE NULL.
SET PTR1 TO ADDRESS OF LINKAGE-THING
SET PTR2 TO PTR1
LINKAGE SECTION.
01 NAME-STRUCTURE.
05 FIRST-NAME PIC X(18).
05 LAST-NAME PIC X(26).
SET ADDRESS OF NAME-STRUCTURE TO EXAMPLE-P.
254. SYNCHRONIZED
• The SYNCHRONIZED clause is sometimes used
with USAGE IS COMP or USAGE IS INDEX
items. It is used to optimize speed of processing
but it does so at the expense of increased
storage requirements.
• The word SYNC can be used instead of
SYNCHRONIZED
• SYNCHRONIZED causes slack bytes to be
generated when needed.
