1.6 Organisation of data Flashcards
What is a file?
A collection of related records stored in the computer and handled as a single unit
What is an archive file?
A single file that often contains multiple files which allows for easier portability and compression so it takes up less storage space.
These files are for record purpose
What is an index file?
A file that contains key field data that can be searched quickly with attached addresses which allow access to a large data file
What is data processing?
The collection and manipulation of items of data to produce meaningful information
What is a record?
A basic data structure in which data is organised in a collection of fields and each field will hold a single piece of data about a person or thing
What is a master file?
A very large file which is a collection of records about a main subject such as customers, employees or products. They contain both descriptive (emails, names and addresses) and summary data (amounts due and year to date sales)
What is serial file access?
Where data items are read in order from where they are physically stored. It doesn’t require data sorting
What is sequential file access?
Where data items are sorted by (and read) in key field order
What is random (direct) file access?
When a data item in a file is accessed directly and not in any physical or programmed order
What is indexed sequential file access?
When an indexes allow direct access to grouped data (e.g. a range 15 - 30) which can be read through sequentially.
Both the index and file must be sorted in order by key field
How are master files updated? (4 steps)
1) The master and transaction file are INPUT to the system
2) The UPDATE process takes place where the transaction file is compared record by record with the master file. The master file is then updated with any new data records
3) NEW updated master file is outputted
4) Required document (e.g. pay roll slips) is outputted
What is batch processing?
This is when data is collected and processed in one single operation with no user interaction. Also errors are stored in a file for later use and are not dealt with as they occur.
Batch processing is usually carried out routinely and is not done during peak high demand times
What are the contents of a file?
Field Name
Data Type
Length
Description
How does an insertion sort work?
Each item is copied one by one by the sorting algorithm and inserted in the correct place in the output
