CHAPTER 2Data

Automatic Data Capture

• Data logging• Barcode reader• Biometrics• OCR• MICR• RFID• Voice Recognition• Smart Card

Data Validation

• Checking carried out by the computer to make sure that input data are within limits of what the user may reasonably enter

Validation Techniques• Range Check• Length Check• Character Check • Format Check

• Limit Check• Presence Check• Consistency Check • Check digit

Calculating check digit• ISBN-10 number: 0-201-53082-?1. Position of each digit is considered and then the position

number and its digit is multiplied:

10 9 8 7 6 5 4 3 2 1

0 – 2 0 1 – 5 3 0 8 2 ? =10x0+9x2+8x0+7x1+6x5+5x3+4x0+3x8+2x2= 98

2. Divide the total by 10 and if remainder, subtract from 10 to give check digit98 / 10 = 9 remainder 810 – 8 = 2

:. 0-201-53082-2

Data Verification

• [Double] checking for accuracy when data are copied into a computer system from paper documents or from another computer. Valid data may still be incorrect, so verification is useful

Verification Techniques• Visual Check• Double-entry

• Parity check Odd parityEven parity

File Organization

• Serial file - according to date of creation• Sequential file - according to record key value

File Maintenance• Inserting a record• Deleting a record• Updating (or amending) a record

Data Types• String• Numeric• Currency

• Date/Time• Boolean• Array

Many data items having

different data types

Many data items having

the same data types

ARRAYS

Data Structure

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