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WJEC - CG1 - 1.2/3
Organization & Structures of Data
| Question | Answer |
|---|---|
| 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
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