IGCSE - ICT - Chapter 11 or 18

file

A collection of related data stored on a lasting medium, such as a hard disk

records

Complete sets of information. They are compromised of fields . A file consists of a set of records.

item

Each piece of data inside a record

field

The space where items are stored

key field

A field in a record that uniquely identifies instances of that record

sequential file

a serial file in order

serial filen

file not sorted in particular order

index

indicate exactly where the record can be found

direct access file

file organized so that a calculation provides the address of a record so that the record can be accessed directly

file maintenance

1. updates and amendments

2. insertions to the file

3. deletions to the files

data type

Indicates the type of data that can be stored in the field

numeric data types

1. integers

2. real numbers (takes up more space)

date data type

A data type that indicates that the data in a field represents a date eg. 07/09/12 or 07/09/2012

alphanumeric data type

contains mainly alphabetic and numeric characters

Boolean data

can be one of two possible values, True or False.

logical data

a data mart created by a relational view of a data warehouse

validation check

to make sure the data entered is validate and followed the rule

types of validation checks

1. length check

2. character check

3. format check

4. presence check

data verification

1. compare output and original

2. input data twice

flat file

Single table with a large number of records and fields

secondary key

Field by which a database is often searched

relational tables

when two files are related and can be referenced

primary key

A field (or group of fields) that uniquely identifies a given entity in a table

foreign key

A key in one field which appears in a field of another file

analogue data

A continuous varying signal, represented using an infinite number of scales. Eg - sound

digital data

Is text, numbers, graphics, sound, and video that has been converted into discrete digits such as 0s and 1s.

analogue to digital converter

A device that changes analogue signals into digital signals

digital to analogue converter

Converts binary words from computer into analogue signals for pixels.