CG1.2 Organization and Structure of Data

CG1.2 Organization and Structure of Data

1. Files, Records & Fields

   • Fixed Length Fields & Records
     • Fixed length fields & records contain a pre-determined amount of data. They are faster to process than variable length fields & records & it is easier to predict how large a file containing these will grow however, they do contain waste space (if a data entry is smaller than the field size then it will be padded with blank spaces until it reaches that size)
   • Variable Length Fields & Records
     • Variable Length Fields & Records are simply fields & records that can hold a changeable amount of data. Files containing these typically take longer to process than files containing fixed length  fields & records, however they also waste less space (one field ends then a character is placed to symbolize its end, then the next field begins immediately)
   • What are Files, Records & Fields
     • A file is a group of related records (such as an account database) A record is a collection of fields based on a particular thing (such as a user account) A field is a single item of data (such as a username/password)

2. File Access

   • Serial & Sequential File Access
     • Serial File Access: Files are stored purely in order of creation (first record created first) Sequential File Access: Files are stored with a different order, such as alphabetical.
   • Algorithm for Serial File Access
     • Open File, Place record in file at end position Close file
   • Algorithm for Sequential File Access
     • Open File Read all records from file & add new record Insertion sort to place new record in correct position Possibly read all records again (to verify that it was correctly sorted) Close File

3. Database Systems

   • Database Management System
     • The Underlying system that manages the database. Its purpose is to assign Access rights & database responsibilities
   • Benefits & Drawbacks of Using a database
     • Using a database lowers the amount of physical space used, the amount of time to edit, sort, retrieve & create, fewer updating issues, data validation, easy to back up, fewer arithmetic errors, generally higher security. Drawbacks of this include people who have poor computer literacy will have issues with the database or that corruption of the database can spread much easier (due to viruses)
   • Data to information
     • Information is data that has been sorted through a query, meaning that it contains only data that adheres to a specific criteria or is related to a specific topic

4. Data Validation & Verification

   • Validation
     • Validation (also known as a machine check) is where data is compared against specific criteria by the program. Examples of validation include Format, Type & Length Checks.
   • Verification
     • Verification (Also known as Human Checks) includes methods such as double-entry (where data is entered twice into a system & then is compared to see if the data is correct)