ICT Unit 5

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  • Created by: Leila
  • Created on: 07-04-15 19:33
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  • ICT Unit 5
    • Files, records, fields and the key field
      • When a school stores information about a student they each have their own record. It may include their name, gender, DOB and contact details.
      • The individual pieces of information recorded on each card, such as name and dat of birth, are called fields.
        • A record must have at least one field. Most files contain a primary key (or key field), the field which uniquely identifies that particular record. With a student this could be their admission number that is unique to each student.
      • Information in computer-based filing systems is stored in data files.
        • A file is a collection of records.
    • Data types
      • For each field, the type of data needs to be specfied:
        • Text- letters of mix of letters and number.
        • Boolean- only two possible entries- Yes/No Male/Female
        • Numeric- numbers
        • Integer- exact whole numbers
        • Date
        • Real- numbers which have a decimal part
        • Currency-real  numbers with always two numbers after the point.
    • Computer databases
      • A database is a structured collection of related data.
      • It can be a single (flat) file that contains a large number of records.
      • Many modern databases are described as being relational.
        • A relational database stores data in tables that are linked together using common fields-the foreign key- which also has to be the primary key in one of the tables.
    • Digital and analogue data
      • Digital data which can only take exact whole number data and when used in computers can only be represented by combinations of either 0s or 1s.
      • Analogue data is data which can take any value and is not restricted to whole numbers, e.g. temperature.
      • Analogue-to-digital converter
        • Measuring devices collect data in analogue form. This must be converted into digital form so that this data can be inputed to the computer system. This is done by an analogue-to-digital converter (ADC)
      • Digital-to-analogue converter
        • After the computer has processed the data, the digital data must be converted into analogue form, by a digital-to-analogue converter (DAC), so that the device can be controlled in the particular application, e.g. turn on a motor to drive the air-conditioning unit.

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