U13 data representation

Question 1

user defined data type

Answer 1

• derived from one or more existing datatypes
• used to extend the built-in datatypes
• programmer’s requirement

Question 2

why are user defined data types necessary

Answer 2

• no suitable datatype is provided by the language used
• if a programmer needs a specific datatype
• that meets program requirements

Question 3

non-composite datatype

Answer 3

• single datatype that does not refer to another datatype
• e.g: enumerated, pointer, real, string, char, boolean

Question 4

composite datatype

Answer 4

• datatype that refers to other datatypes
• data type is constructed from other datatypes
• e.g: record, list, set, array, class, queue, linked list, dictionary

Question 5

record

Answer 5

collection of related items which may be of different datatypes

Question 6

list

Answer 6

indexed collection that can contain different datatypes

Question 7

set

Answer 7

supports mathematical operation

Question 8

class

Answer 8

gives properties and methods for an object

Question 9

array

Answer 9

collection of items of the same datatype

Question 10

enumerated datatype

Answer 10

• non-composite
• defined by a given list of all possible values
• in an order

Question 11

pointer datatype

Answer 11

• non-composite
• used to reference a memory location

Question 12

dereferencing

Answer 12

getting the value in an address

Question 12

record datatype

Answer 12

• composite datatype
• a collection of multiple datatypes

Question 13

declaring a range

Answer 13

• 0-89
• DECLARE number : 0..89

Question 14

file organization

Answer 14

refers to the way data is stored in a file

Question 15

serial file organization

Answer 15

• data is stored in chronological order
• easy to append data to the end of the file
• allows the data to be read in order of when they were taken
• no KEY FIELDS need to be added

Question 16

when is serial used

Answer 16

• when chronological order matters
• appending records
• small file, so easy to search
• when re-organizing as re-sorting is not required

Question 17

sequential file organization

Answer 17

• a method of file organization in which files are stored with ordered records
• records are stored in the order of the key fields
• new records are inserted into their correct position

Question 18

when is sequential used

Answer 18

• when there are unique fields, so it can be used for indexing
• when it needs to be sorted in an order
• batch processing (processing of transaction in a group)

Question 19

random file organization

Answer 19

• record location is calculated
• using a hashing algorithm on a key field
• speed of data access is increased
• can be used as lookup file
• if a record cannot be stored
• then subsequent location is searched (closed hash)
• or an overflow area is searched (open hash - chaining)

Question 20

hashing algorithm

Answer 20

a mathematical function to find a hash key to access data

Question 21

bucketing (closed hashing)

Answer 21

a method to deal with hashing collisions in which another empty space is found

Question 22

chaining (open hashing)

Answer 22

a method to deal with hashing collisions in which linked lists are used to find the location in ROM

Question 23

rehashing (closed hashing)

Answer 23

a method to deal with hashing collisions in which another algorithm is used

Question 24

how is sequential access used

Answer 24

• earliest reading/data is accessed first
• each successive reading is read
• until final reading is accessed

Question 25

floating point representation

Answer 25

representation of real numbers

Question 26

mantissa

Answer 26

the significant digits of floating point number

Question 27

exponent

Answer 27

the power of base 2 (that the mantissa is raised to)

Question 28

normalization

Answer 28

a technique that is used to make your data more accurate

Question 29

random file

Answer 29

• can be read/write at the same time
• contains a collection of data
• normally as records of a fixed length
• can be thought of as having a file pointer that can be moved to any location or address of the file
• record at that location can then be read or written