U13.2 data representation

Question 1

file organization

Answer 1

refers to the way data is stored in a file

Question 2

serial file organization

Answer 2

• 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 3

when is serial used

Answer 3

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

Question 4

sequential file organization

Answer 4

• 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 5

when is sequential used

Answer 5

• 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 6

random file organization

Answer 6

• 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 7

hashing algorithm

Answer 7

a mathematical function to find a hash key to access data

Question 8

bucketing (closed hashing)

Answer 8

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

Question 9

chaining (open hashing)

Answer 9

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

Question 10

rehashing (closed hashing)

Answer 10

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

Question 11

how is sequential access used

Answer 11

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

Question 12

random file

Answer 12

• 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