SYSTEMSDESIGNANALYSIS 1 Chapter 19 Data Entry Procedures Jerry Post Copyright © 1997

SYSTEMSDESIGN 2 Goals  Collect accurate data.  Effective data coding.  Efficient data capture and entry.  Data validation.

SYSTEMSDESIGN 3 Data Encoding  Simple ID Numbers  Sequential Easy to create. Problems if mistype by one number.  Alphabetic Hide the count. Contain additional information.  Classification codes  e.g., M=male, F=female  Block sequence  Sequential numbers assigned to categories = spreadsheet = database  Codes to conceal  e.g., hide prices  Simple substitution ciphers (substitute one letter for a number, etc.)  Codes to provide information  Categories (significant digit) e.g., Dept.202 Prod.395 Color40 Size10  Mnemonic codes e.g., airports: STL, LAX, SLC

SYSTEMSDESIGN 4 Guidelines for Creating Codes  Be concise.  Keep the codes stable.  Assure that codes are unique.  Allow codes to be sortable.  Avoid confusing codes.  Keep codes uniform.  Allow for modification an expansion.  Make codes meaningful.  Add check-digits.  Bad examples:   170AB, QQ9882, 2O008  Apr495, Mar396, Dec1595  1lS52ZO0  Better examples:  125, 998, 253  170AB, 982QQ, 291QB  , ,

SYSTEMSDESIGN 5 Effective and Efficient Data Capture  Decide what to capture.  Let the computer look up data.  Let the computer do computations.  Avoid bottlenecks and extra steps.  Start with a good form (especially drop-down boxes).  Avoid batch data-entry.  Collect data as close to the source as possible.  Entry options  Optical character recognition (OCR).  Magnetic ink character recognition (MICR).  Mark-sense forms.  Punch-out forms.  Bar codes.  On-line/customer entry (Web site).

SYSTEMSDESIGN 6 Data Validation  Validating input transactions (errors to avoid).  Submitting the wrong data.  Submitting data by an unauthorized person.  Asking the system to perform an unacceptable function.  Validating input data  Test for missing data.  Test for correct field length.  Test for class or composition.  Test for range or reasonableness.  Test for invalid values.  Test for comparison with stored data.  Design self-validating codes (check digits).

SYSTEMSDESIGN 7 Check Digits  Add a digit to the end of the code that is based on the earlier digits.  Need weights for each position.  Catch transposition.  Catch double errors.  Strongest is Cyclic Redundancy Check (CRC).  Fits a polynomial to data.  Catches most common errors.  Algorithm is in CS books. Code: Weights (1 x 3), Modulus: 10 5*1 = 5 4*3 = 12 8*1 = 8 2*3 = 6 3*1 = 3 Add: = 34 Get modulus: 34/10 = 3, remainder = 4 (Optional: = 6) New code: