Embed Size (px)
Citation preview
1
Chapter 5 – The Procedure Division• File handling statements
– OPEN statement• Initiates processing for a file• Input• Output• Each file opened must have been referenced in the
select statement in the environment division• And in a corresponding FD in the data division
– CLOSE statement• Use when access to a file is no longer necessary• Files should be closed before processing terminates• Usually immediately before the STOP command
2
– READ statement
• Transfers data from an open file into memory• AT END clause
– If file is at the end control transfer to this clause
READ file-name
AT END statement
END-READ
• Primimg the READ• Correct positioning
3
– WRITE• Transfers data from memory to an output
device– Printer, Open File
• ADVANCING (AFTER & BEFORE)– For printer usage, printing blank lines– LINES and PAGE
• Contains a Record name– 01 Entry in the File Section of the Data Division
MOVE SPACES TO OUT-LABEL-REC.
MOVE IN-EMPLOYEE-NAME TO WS-EMPLOYEE-NAME.
MOVE WS-NAME-LINE TO OUT-LABEL-REC.
WRITE OUT-LABEL-REC.
4
• Data manipulation and program statements– DISPLAY statement– STOP RUN statement
• Terminates the program• Should not be more than one in your program• Typically not the last statement
– MOVE statement• Copies data from one location to another• Syntax
– MOVE 15 TO NUM-1 NUM-2 NUM-3.
• Restrictions on use• Rules for use• Group Moves
5
Table 5.1 Rules of the MOVE Statement (Elementary Data Items)
SENDING FIELD RECEIVING FIELD
Alphabetic
Alphanumeric
Numeric
Numeric Edited
ALPHABETIC ALPHANUMERIC NUMERIC NUMERIC EDITED
Valid
Invalid
Invalid
Invalid
Valid
Valid
Integers Only
Valid
Invalid
Invalid
Valid
Valid
Invalid
Invalid
Valid
Invalid
6
Table 5.2 Illustration of the MOVE statement: Alphanumeric Sending Field to Alphanumeric Receiving Field
SENDING FIELD RECEIVING FIELD
PICTURE CONTENTS PICTURE CONTENTS
(a) X(5) A B C D E X(5) A B C D E
(b) X(5) A B C D E X(4) A B C D
(c) X(5) A B C D E X(6) A B C D E F
7
Table 5.3 Illustration of the MOVE statement: Numeric Sending Field to Numeric Receiving Field
SENDING FIELD RECEIVING FIELD
PICTURE CONTENTS PICTURE CONTENTS
(a) 9(5) 1 2 3 4 5 9(5) 1 2 3 4 5
(b) 9(5) 1 2 3 4 5 9(4) 2 3 4 5
(c) 9(5) 1 2 3 4 5 9(6) 0 1 2 3 4 5
(d) 9(3)V99 1 2 3 v 4 5 9(3) 1 2 3
(e) 9(3)V99 1 2 3 v 4 5 9V99 3 v 4 5
(f) 9(3) 1 2 3 9(3)V99 1 2 3 v 0 0
8
– PERFORM statement• Transfers control to a procedure (paragraph)• Returns to the next line of code after it was
called• Use of UNTIL
– Checks before it transfers control
– IF statement• ELSE clause• END-IF• Use of indentation
9
CONDITION?
STATEMENT2 STATEMENT1
STATEMENT3
CONDITION?
STATEMENT1
STATEMENT2
Figure 5.2 The IF Statement
(a) With ELSE Option (b) Without ELSE Option
FALSEFALSE
TRUETRUE
10
Figure 5.3 The ELSE Clause/II
A=B
MOVE ZERO TO C
MOVE 1 TO C
WRITEDETAIL-LINE
MOVE ZERO TO D
MOVE 1 TO D
FALSE TRUE
IF A = B
MOVE 1 TO C
MOVE 1 TO D
ELSE
MOVE ZERO TO C
MOVE ZERO TO D
END-IF.
WRITE DETAIL-LINE.
(a) IF/ELSE Flowchart (b) COBOL Code
11
– EVALUATE statement
• Similar to a case statement
EVALUATE TRUE
WHEN STU-CREDITS <= 6
MOVE 25 TO IND-ACTIVITY-FEE
WHEN STU-CREDITS > 6 AND STU-CREDITS <=12
MOVE 50 TO IND-ACTIVITY-FEE
WHEN STU-CREDITS > 12
MOVE 75 TO IND-ACTIVITY-FEE
END-EVALUATE
12
Arithmetic Verbs
• ROUNDED clause– Rounds the answer an arithmetic statement– If no rounded clause is used it truncates– ADD A B GIVING C ROUNDED
• SIZE ERROR clause– Creates an warning when result of a calculation is
to big for the designated field– You can use this to compensate for larger
numbers.– ON SIZE ERROR PERFORM …
13
Table 5.4 The ROUNDED Clause
DATA NAME A B C
PICTURE 9V99 9V99 9V9Value before execution 123 456 (immaterial)
Value after execution of:
ADD A B GIVING C 123 456 57
ADD A B GIVING C ROUNDED 123 456 58
14
• The COMPUTE statement
– Combines multiple arithmetic operations– Ex.) COMPUTE A = a * b + c– +,-,*,/,**– Order:
• Parentheses• Exponentiation• Multiplication, division• Addition, subtraction
15
Table 5.5 The COMPUTE Instruction
DATA NAME A B C COMMENTSValue before execution 2 3 10 Initial Values
Value after execution of:
COMPUTE C = A + B. 2 3 5 Simple addition
COMPUTE C = A + B * 2. 2 3 8 Multiplication before addition
COMPUTE C = (A + B) * 2. 2 3 10 Parenthesis evaluated first
COMPUTE C = A ** B. 2 3 8 algebraically, c = ab
COMPUTE C = B ** A. 2 3 9 algebraically, c = ba
16
Table 5.6 The COMPUTE Instruction (continued)
ALGEBRAIC EXPRESSION COBOL COMPUTE
x = a + b COMPUTE X = A + B.
x = a + b COMPUTE X = (A + B) / 2. 2
x = (a + b)c COMPUTE X = (A + B) * C / 2. 2
x = a + b COMPUTE X = (A + B) / (2 * C). 2c
x = a COMPUTE X = A ** .5.
x = a + b COMPUTE X = (A ** 2 + B ** 2) / C ** 2 c2
17
• The ADD statement
• The SUBTRACT statement
• The MULTIPLY statement
• The DIVIDE statement
• Assumed decimal point
• The COMPUTE statement for multiple operations
18
Table 5.7 The ADD Instruction
DATA NAME A B C
Value before execution 5 10 30
Value after execution of:
ADD A TO C 5 10 35
ADD A B TO C 5 10 45
ADD A TO B GIVING C 5 10 15
ADD A 18 B GIVING C 5 10 33
ADD A 18 B TO C 5 10 63
ADD 1 TO B C 5 11 31
19
Table 5.8 The SUBTRACT Instruction
DATA NAME A B C D
Value before execution 5 10 30 100
Value after execution of:
SUBTRACT A FROM C 5 10 25 100
SUBTRACT A B FROM C 5 10 15 100
SUBTRACT A B FROM C GIVING D 5 10 30 15
SUBTRACT 10 FROM C D 5 10 20 90
20
Table 5.9 The MULTIPLY Instruction
DATA NAME A B C
Value before execution 5 10 30
Value after execution of:
MULTIPLY B BY A GIVING C 5 10 50
MULTIPLY A BY B GIVING C 5 10 50
MULTIPLY A BY B 5 50 15
MULTIPLY B BY A 50 10 30
MULTIPLY A BY 3 GIVING B C 5 15 15
21
Table 5.10 The DIVIDE Instruction
DATA NAME A B C
Value before execution 5 10 30
Value after execution of:
DIVIDE 2 INTO B. 5 5 30
DIVIDE 2 INTO B GIVING C. 5 10 5
DIVIDE B BY 5 GIVING A 2 10 30
DIVIDE A INTO B C 5 2 6
DIVIDE A INTO B GIVING C 5 10 2
DIVIDE 3 INTO A GIVING B REMAINDER C 5 1 2
22
DATA NAME A B C
PICTURE 99 99V9 99V99Value before execution 12 345 4712
Value after execution of:
ADD B TO A 46 345 4712
ADD A TO B 12 465 4712
ADD B TO C 12 345 8162
ADD C TO B 12 816 4712
ADD C TO A 59 345 4712
ADD A TO C 12 465 5912
Table 5.11 Arithmetic on Fields with Assumed Decimal Points
23
Use the COMPUTE Statement for Multiple Arithmetic Operations
MULTIPLY B BY B GIVING B-SQUARED.MULTIPLY 4 BY A GIVING FOUR-A.MULTIPLY FOUR-A BY C GIVING FOUR-A-C.SUBTRACT FOUR-A-C FROM B-SQUARED GIVING RESULT-1.COMPUTE RESULT-2 = RESULT-1 ** .5.SUBTRACT B FROM RESULT-2 GIVING NUMERATOR.MULTIPLY 2 BY A GIVING DENOMINATOR.DIVIDE NUMERATOR BY DENOMINATOR GIVING X.
COMPUTE X = (-B + (B ** 2 - ( 4 * A * C)) ** .5) / ( 2 * A).
Both sets of code apply to the quadratic formula
X = -B + B-4AC 2A
Poor Code
Improved Code
PROGRAMMING TIP
24
Problems
A B C D
4 8 12 2
ADD 1 TO D B
ADD A B C GIVING C
MULTIPLY A BY B C
COMPUTE D=A+B/2*D
COMPUTE D=(A+B)/(2*D)
25
Problems
X = a + b + c
X = a2 + b2 + c2
F = p(1+I)n
26
Problems
Sending field Receiving field
X(4) HOPE X3
X(4) HOPE X5
9(4) 6789 9(5)
999V9 6789 9(3)V99
27
Figure 5.4a Developing the Procedure Division
PREPARETUITIONREPORT
WRITEHEADING
LINE
READSTUDENT
FILE
PROCESSSTUDENTRECORD
WRITEUNIVERSITY
TOTALS
COMPUTETUITION
COMPUTEUNION FEE
COMPUTEACTIVITY
FEE
COMPUTESCHOLARSHIP
COMPUTEINDIVIDUAL
BILL
INCREMENTUNIVERSITY
TOTALS
WRITEDETAIL
LINE
READSTUDENT
FILE
(a) Hierarchy Chart
28
Open filesWrite heading line(s)Read STUDENT-FILE at end indicate no more dataDO WHILE data remains Compute tuition = 200 * credits IF union member
Union fee = $25 ELSE
Union fee = $0 ENDIF DO CASE
CASE credits <= 6 Activity fee = 25CASE credits > 6 and < 12 Activity fee = 50CASE credits >= 12 Activity fee = 75
END CASE IF gpa > 2.5
Scholarship = Scholarship amount ELSE (no scholarship)
Scholarship = 0 ENDIF Compute Bill = Tuition + Union fee + Activity fee - Scholarship Increment university totals Write detail line Read STUDENT-FILE at end indicate no more dataENDDOWrite university totalsClose filesStop run
(b) Detailed Pseudocode
Figure 5.4b Developing the Procedure Division
29
SMITH JB15Y0000230JAMES HR15 0500245BAKER SR09 0500350PART-TIMER JR03Y0000300JONES PL15Y0000280HEAVYWORKER HM18 0000200LEE BL18 0000335CLARK JC06 0000310GROSSMAN SE07 0000215FRANKEL LF10 0000350BENWAY CT03 0250395KERBEL NB04 0000100
STUDENT NAME CREDITS TUITION UNION FEE ACT FEE SCHOLARSHIP TOTAL BILL
SMITH JB 15 003000 025 075 00000 003100JAMES HR 15 003000 000 075 00000 003075BAKER SR 09 001800 000 050 00500 001350PART-TIMER JR 03 000600 025 025 00000 000650JONES PL 15 003000 025 075 00000 003100HEAVYWORKER HM 18 003600 000 075 00000 003675LEE BL 18 003600 000 075 00000 003675CLARK JC 06 001200 000 025 00000 001225GROSSMAN SE 07 001400 000 050 00000 001450FRANKEL LF 10 002000 000 050 00000 002050BENWAY CT 03 000600 000 025 00250 000375KERBEL NB 04 000800 000 025 00000 000825 ------- ---- ----- ------ -------
UNIVERSITY TOTALS 024600 0075 0625 000750 024550
(a) Test Data
(b) Output
Figure 5.6 Test Data and Output
30
Figure 5.7 Skeleton Outline of a COBOL Program
IDENTIFICATION DIVISION.PROGRAM-ID. PROGNAME.AUTHOR. JOHN DOE.
ENVIRONMENT DIVISION.INPUT-OUTPUT SECTION.FILE-CONTROL. SELECT INPUT-FILE ASSIGN TO ‘A:\CHAPTR05\TUITION.DAT’
ORGANIZATION IS LINE SEQUENTIAL. SELECT PRINT-FILE
ASSIGN TO PRINTER.
DATA DIVISION.FILE SECTION.FD INPUT-FILE RECORD CONTAINS 80 CHARACTERS.01 INPUT-RECORD PIC X(80).
FD PRINT-FILE RECORD CONTAINS 132 CHARACTERS.01 PRINT-LINE PIC X(132).
WORKING-STORAGE SECTION.01 DATA-REMAINS-SWITCH PIC X(2) VALUE SPACES.01 HEADING-LINE.. .01 DETAIL-LINE.. .01 TOTAL-LINE.. .
SELECT statements for input and output files
Controls performed paragraph
31
Figure 5.7 Skeleton Outline of a COBOL Program(cont.)
PROCEDURE DIVISION.MAINLINE.
OPEN INPUT INPUT-FILE OUTPUT PRINT-FILE. READ INPUT-FILE AT END MOVE ‘NO’ TO DATA-REMAINS-SWITCH END-READ. PERFORM PROCESS-RECORDS UNTIL DATA-REMAINS-SWITCH = ‘NO’. CLOSE INPUT-FILE PRINT-FILE. STOP RUN.
PROCESS-RECORDS.. .
READ INPUT-FILE AT END MOVE ‘NO’ TO DATA-REMAINS-SWITCH END-READ.
Housekeeping consists of opening files and the initial READ
Termination includes closing files and STOP RUN.
Last line of performed paragraph is a second READ
32
Tuition Billing Program
•
