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WJEC - CG1 - 1.2/3

Organization & Structures of Data

QuestionAnswer
Name five data types - String - Integer - Character - Boolean - Date
Define a Primary Key A unique field of a record used to identify the record
Define a Field A field is a single item of data
Define a Record A record is a collection of items all relating to an object and is treated as a single item for processing
Define a Fixed Length Record A record that contains the same number of bytes in each record.
Define a Variable Length Record A record that may have a different number of bytes in each record
Advantages & Disadvantages - Fixed length Record - Quicker to Process, as start and end locations are known - Easier to Program/Estimate storage requirements - May waste space - fixed lengths will truncate (limit) long fields
Advantages & Disadvantages - Variable length Record - Saves on storage space as no blank spaces are present - Avoids Truncation - Makes calculating storage requirments tricky - Slower to process as start and end locations aren't known
What is a Serial File A database where records arent added or stored in any particular order. (Think Serial Killer)
What is a Sequential File A database where records are added and sorted in an order, usually via a primary key
How is a record added in a Sequential File A new file is made by copying the old file up to the point of insertion, added the new record and then copying the rest of the file creating a new completed file
What is a Master File A usually permanent data store used by the business to store all important information.
What is a Transaction File A file that contains temporary data that will be added to the master file
What are some Disadvantages of using a paper based system - Paperwork may get lost - Difficult/Time consuming to find customer details - Paper based systems are difficult to back up each piece of paper individually - Time consuming to amend customer details - Difficult to sort data into a usable order
Advantages of a Database - easy to search for data by a criteria or field name - Easier to back up a computerized database - Easy to add data to a database - Data can be sorted easily in a database - Font is clear and easy to read - Automated features like mail merge
Is validation for checking data going in or checking data that is already in to a database Checking data going into a database
Name some validation methods - Presence Check - Range Check - Type Check - Format Check - Look-up Check - length Check
Describe what they do - Checks if data is present - Checks if numerical data is within a range - Checks data type (integer etc) - Checks if the format of the data is correct (post code etc) - Using a drop down box - Checks the char' length of a string
When data is copied from a data capture form, this is called what Transcribing
Name some verification methods - Screen verification - Double Keying - Check Digit
Explain these methods - This sends data entered back to the source so that they may check its accuracy (author proof reading) - Entering the same data twice to avoid errors - A number that is generated as a result of the imputed value. (last digit of a bar code)
Describe an array A list/collection of items/elements that is all of the same datatype
Difference between a 2d and a 3d array may contain more then one type of data
Created by: delldom