Flashcards
1.3 Data; Its Representation, Structure & Management
Cards in this deck (25)
- 1What is a Bit?A single 1 or 0
groups of these are used to represent characters - 2What is a Byte?A series of 8 bits used to represent chatacters
- 3What is a Character Set?The complete range on Characters used by a computer.
Each character has a unique binary code.
Agreed character sets include
ASCII - 8 bit
UNICODE - 16 bit (multi-language: 65000 characters)
ANSI - used for shapes and graphical symbols - 4What is Numeric Data?Real Numbers allow decimals (3.141)
Integers are Whole numbers only (779)
A short integer uses 1,2 or 4 bytes
(0-32767 0r 65535)
Remember a negative sign uses one of the bits - 5What is Boolean Data?Only one of two possible answers can be stored. Represented as
Yes/No
True/False
On/Off
All stored as -1/0 - 6What is character data? What is String Data?A single character e.g. Z
A String is a collection of characters, perhaps a single word or more. - 7What is an Array?A Variable with a specified number of elements or Subscripts.
Memory locations are reserved for these elements allowing fast retrieval. - 8What is meant by; Dim ListOfNames(50) As StringArray Name = ListOfNames;
Data Type = String;
Number of Subscripts = 51;
Lower bound = 0;
Upper bound = 50; - 9What is a FIFO queue?A queue such as a Printer Job Queue which is processed in accord with the principle of First Job In is the First Job Out
- 10How is a Queue Managed?By using a Start Pointer (sp) and and End Pointer (ep);
sp = the next job to do
ep = the position to place the next job coming into the queue - 11What is a Stack? (used in recursion)Where the job that is processed next is the LAST one to arrive and not the FIRST;
LIFO not FIFO - 12What is a File?A collection of related records. Sometimes referred to as a table.
- 13What is a Record?A row of related fields in a file or table for example a Student record
- 14What is a Field?The container for each type of information stored in a record for Example - Surname or DOB
- 15What is a Data Item?The data contents of a Field for example: Smith or 25/05/1998
- 16What is a Key Field?A Field which holds a UNIQUE value used to identify a Record. E.g StudentNumber or OrderID
- 17What is a Fixed Length Record?Where storage space is set for each field e.g Surname 50 characters. Can lead to unused space but is faster to search and organise data
- 18What is Serial Access?Data are accessed in the chronological order in when it arrived in the file. The words in a book for example.
- 19What is Sequential Access?Data stored in sequence using a Key Field. A file sorted by an order for example (Surname, DOB). Searching is carried out by starting at the beginning of a file
- 20What is Indexed Sequential Access?A file of records organised by a separate index. For example the Phone book where you can begin a search from a point indicated by the index - J
- 21What is Random Access?Data stored in no particular order. However, the data is used in an algorithm (Hashing) to determine location. Collision or Clashes need to be handled. Can lead to unused space.
- 22What is Backing-Up Data?A re-storable copy of data to be used in the event of data loss
- 23What types of Back-Up can there be?1. Full: All data backed up every time.
2. Incremental only changed data is backed up - 24Good Back-Up Policy might include1 - Regular Schedule. 2 - Record log of Back-Ups. 3 - Separate physical location for storage. 4 - more important data backed-up more frequently.
- 25What is Archiving?Storage of Data that may yet be needed in the future but is not considered as current. For example former pupil records or Order details over 5 years old.
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- Flashcards on 1.3 Data; Its Representation, Structure & Management, created by messagekm on 12/03/2014.
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