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Chapter 2: Data Organization and Control 4C Abbey Sin 24 4C Chan Chloe 3,…
Chapter 2: Data Organization and Control 4C Abbey Sin 24
4C Chan Chloe 3
2.1 Data Input &
Source of Errors
Errors
Transposition error
Data source error
Transcription error
Garbage-In-Garbage-Out(GIGO)
2.2: Data Control
Data validation
Field presence check
Field length check
Range check
Fixed value check
Format check
Type check
Check digit
Parity
ISBN
Data verification
Input data twice
Double data entry
2.3:Data Hierarchy
Database
Collection of tables
Links different tables with key fields
Table
Collection of records
Record
Collection of fields
Field
Smallest unit of data
Key field - unique data
2.4 Database Management System (DBMS)
Oranizing tables
Modify table
Delete table
Create table
Managing records in a table
Delete existing records
Modify existing records
Add a new record
Browse records
Essential features
Index
Data entry forms
Sort
Query forms
Filter
Reports
2.5: File Access Mode
Sequential access
e.g. VHS tape
Mainly used in magnetic tapes
Direct access
e.g. Hard disk (platters)
Shorter seek time
https://www.youtube.com/watch?v=R2ocgaq6d5s
