Chapter 8 Data Validation Data validation Incoming data

Chapter 8 – Data Validation • Data validation – Incoming data must be check to avoid errors – Numeric test – Alphabetic test – Reasonableness check • Limit/Range checks – number is within limits – Consistency check • Comparing two fields against eachother 1

– Existing code check • Omission errors – full statements in your IFs – Sequence check • Incoming records are in the correct order – Completeness check • Makes sure that all the fields in any record contain data – Date check • Checks that incoming date is logical 2

• The IF statement – Relational condition – Class test • NUMERIC clause • ALPHABETIC clause – Sign test • POSITIVE clause • NEGATIVE clause • ZERO clause 3

Figure 8. 1 IF The Relational Condition identifier-1 literal-1 expression-1 IS [NOT] GREATER THAN IS [NOT] > IS [NOT] LESS THAN IS [NOT] < IS [NOT] EQUAL TO IS [NOT] = IS [NOT] GREATER THAN OR EQUAL TO IS [NOT] >= IS [NOT] LESS THAN OR EQUAL TO IS [NOT] <= identifier-2 literal-2 expression-2 (a) Syntax 05 NUMERIC-FIELD PIC 9(5). 05 ALPHANUMERIC-FIELD PIC X(5). . IF NUMERIC-FIELD = 10. . . IF NUMERIC-FIELD = ‘ 10’. . . IF ALPHANUMERIC-FIELD = 10 IF ALPHANUMERIC-FIELD = ‘ 10’ (b) Examples (valid entry) (invalid entry) (valid entry) 4

Figure 8. 2 The Class Test IF identifier IS [NOT] NUMERIC ALPHABETIC-UPPER ALPHABETIC-LOWER (a) Syntax 05 NUMERIC-FIELD PIC 9(5). 05 ALPHABETIC-FIELD PIC X(5). . IF NUMERIC-FIELD IS NUMERIC PERFORM D 0 -ARITHMETIC-CALCULATIONS END-IF. IF NUMERIC-FIELD IS NOT NUMERIC DISPLAY ‘ERROR - NUMERIC FIELD CONTAINS INVALID DATA’ END-IF. IF ALPHABETIC-FIELD IS ALPHABETIC DISPLAY ‘ALPHABETIC FIELD CONTAINS UPPER AND/OR LOWER CASE LETTERS’ END-IF. IF ALPHABETIC-FIELD IS NOTALPHABETIC DISPLAY ‘ERROR - ALPHABETIC FIELD CONTAINS NON-ALPHABETIC DATA’ END-IF. (b) Examples 5

Figure 8. 3 The Sign. Test identifier IF arithmetic expression IS [NOT] POSITIVE NEGATIVE ZERO (a) Syntax IF NET-PAY IS NOT POSITIVE PERFORM TOO-MUCH-TAXES END-IF. IF CHECK-BALANCE IS NEGATIVE PERFORM OVERDRAWN END-IF. (b) Examples 6

• Compound test – Operators • AND expression • OR expression • NOT expression – Precedence of operators • Arithmetic, Relational, NOT, AND, OR • Effect of parenthesis – Implied conditions • IF TERM > 6 and TERM < 12 THEN IF TERM > 6 AND < 12 THEN 7

Figure 8. 5 NO FALSE Compound Conditions A>B? NO YES C>D? FALSE (a) A > B AND C > D NO YES TRUE NO FALSE C>D? A>B? YES FALSE TRUE (b) A > B OR C > D 8

– Nested IF statements • ELSE clause – Comparing a Date to Today’s date 9

Figure 8. 6 Nested IF Statements NO NO MOVE B TO BIG C>B? A>B? YES NO MOVE C TO BIG A>C? YES MOVE A TO BIG (a) Flowchart 10

Figure 8. 6 Nested IF Statements IF A > B IF A > C MOVE A TO BIG ELSE MOVE C TO BIG END-IF ELSE IF C > B MOVE C TO BIG ELSE MOVE B TO BIG END-IF. (b) COBOL Statements 11

Figure 8. 8 The ACCEPT Statement WORKING-STORAGE SECTION. 01 EMPLOYEE-RECORD. . . 05 EMP-DATE-OF-BIRTH. 10 EMP-BIRTH-MONTH 10 EMP-BIRTH-YEAR PIC 99. 01 EMPLOYEE-AGE PIC 99 V 99. 01 DATE-WORK-AREA. 05 TODAYS-YEAR PIC 99. 05 TODAYS-MONTH PIC 99. 05 TODAYS-DAY PIC 99. . . PROCEDURE DIVISION. . . ACCEPT DATE-WORK-AREA FROM DATE. . . COMPUTE EMPLOYEE-AGE = TODAYS-YEAR - EMP-BIRTH-YEAR + (TODAYS-MONTH - EMP-BIRTH-MONTH) / 12. 12

Figure 8. 10 (continued) ERROR REPORT AS OF 07/03/98 CONTRACT # LAST NAME ERROR MESSAGE & FIELD CONTENTS 123459 BAKER INVALID DAY INSURANCE CODE MUST BE Y OR N X 04/31 987651 BROWN MILES DRIVEN UNREASONABLY LOW DAYS: 10 MILES: 000010 999999 JONES MONTH MUST BE BETWEEN 1 AND 12 MILEAGE IN LESS THAN MILEAGE OUT NON-NUMERIC MILEAGE RATE 13 IN: 004500 OUT: 004600 O 5 987655 BROWNING CAR TYPE MUST BE: E, C, M, F, OR L DATE HAS NOT YET OCCURRED 10/24/98 NON-NUMERIC MILES IN OO 2400 0 655443 FITZPATRICK INVALID DAY INSURANCE CODE MUST BE Y OR N C 05/32 PINNOCK PINNOCK NON-NUMERIC CONTRACT NUMBER MISSING FIRST NAME NON ALPHABETIC INITIAL DATE YAS NOT YET OCCURRED 10/12/98 NON-NUMERIC MILES OUT BUTLER NON-NUMERIC CONTRACT NUMBER X 93477 INVALID DAYS RENTED MUST BE > ZERO 00 MILEAGE RATE OUT OF RANGE X 93477 84644 O 84644 O NON-NUMERIC CONTRACT NUMBER 84644 O MISSING LAST NAME CAR TYPE MUST BE: E, C, M, F, OR L DAYS RENTED MUST BE NUMERIC I 5 MILES DRIVEN UNREASONABLY LOW (b) Error Report 1 OO 3310 06/31 75 X DAYS: I 5 MILES: 000125 13

• A data validation program – Specifications – Program design – Program listing – Exception report 14