Chapter 2

Question 1

What data represents?

Answer 1

represents a fact or character-istic about an object of interest to us

Question 2

File

Answer 2

A collection of facts that describes a particular object

Question 3

Record

Answer 3

a row of a file; this represents the data that we have on one instance of the file object

Question 4

Field

Answer 4

a column of a file; this represents the data we have for one characteristic, or attribute, of all instances of the file object

Question 5

A key field for a data table contains?

Answer 5

data values that are unique in the file; that is, each record will always have a different value for that field than all other records

Question 6

fundamental operations -Read

Answer 6

looking at a record’s contents without changing them

Question 7

fundamental operations-Insert

Answer 7

adding a new record to the file, as when a new salesperson is hired

Question 8

fundamental operations-Update

Answer 8

changing one or more of a record’s field values

Question 9

fundamental operations-Delete

Answer 9

deleting a record from the file, as when a salesperson leaves the company

Question 10

Primary Memory

Answer 10

where computers execute programs and process data

• Also known as RAM (random access memory)
• Very fast data access
• Has several drawbacks
• relatively expensive
• not transportable
• volatile (contents are lost without power)

Question 11

Secondary Memory

Answer 11

can store vast volumes of data and the programs that process them

Question 12

Access Arm Mechanism

Answer 12

The basic disk drive has one access arm mechanism with arms that can reach in between the disks
At the end of each arm are two read/write heads
The platters spin, all together as a single unit, on the central spindle, at a high velocity

Question 13

Steps in Finding and Transferring Data- Seek Time

Answer 13

The time it takes to move the access arm mechanism to the correct cylinder from the cylinder at which it’s currently positioned

Question 14

Steps in Finding and Transferring Data- Head Switching

Answer 14

• Selecting the read/write head to access the platter for the required track of the cylinder

Question 15

Steps in Finding and Transferring Data- Rotational Delay

Answer 15

• Waiting for the desired data on the track to arrive under the read/write head as the disk is spinning

Question 16

Steps in Finding and Transferring Data- Transfer Time

Answer 16

The time to actually move the data from the disk to primary memory once the previous 3 steps have been completed

Question 17

Data Retrieval Methods– Sequential Access

Answer 17

• the retrieval of all or most of the records of a file one after another, in some sequence, starting from the beginning, until all of the required records have been retrieved
  However, this method is very inefficient when one or a few records are sought in no set order

Question 18

Data Retrieval Methods- Direct Access

Answer 18

the retrieval of a single record of a file, or a subset of the records of a file, based on one or more values of a field or a combination of fields in the file

Sometimes called random access

Requires software that will take advantage of the hardware’s capabilities and store and retrieve the data in such a way that it accomplishes direct access

Question 19

Indexing

Answer 19

Principal is the same as that governing the index in the back of a book
An index file, separate from the main data file, is created

Question 20

Hashing

Answer 20

is a file access method that allows for direct access of data without creating indexes

Question 21

Hashing–division-remainder

Answer 21

Divide the key value of the desired record by the number of record locations that have been reserved; discard the quotient, and use the remainder to specify where to locate the record

Question 22

Database Characteristics

Answer 22

• Contain ordered collections of data
• Contain related or linked data elements
• Designed to satisfy specific information needs
• Provide shared data access to multiple users

Question 23

Data repository

Answer 23

storage unit where physical data files are kept

Question 24

Data dictionary

Answer 24

location where definitions of data (metadata) are maintained

Question 25

Database software

Answer 25

synonym for DBMS

Question 26

Data abstraction

Answer 26

grouping and presentation of data to meet the needs of different sets of users

Question 27

Data access

Answer 27

read, insert, update, and delete

Question 28

Transaction support

Answer 28

provision of reliable multi- step business process capability (e.g., order entry)

Question 29

Parent-child relationship:

Answer 29

Relationship between pair of data structures at adjacent levels

Question 30

Relational Database Model- A table

Answer 30

the fundamental data storage object of relational databases

Question 31

Primary key

Answer 31

Enforces uniqueness for each record

Question 32

Foreign keys

Answer 32

Define relationships between tables

–Act as linking fields to connect tables

Question 33

Object-relational database management systems (ORDBMS) combine:

Answer 33

Ability of object technology to handle advanced relationship types
Data integrity, reliability, and recovery features of the traditional relational model

Question 34

DBMS Components–Database engine

Answer 34

provides core functionality

Question 35

DBMS Components–Query processor

Answer 35

handles query optimization and execution

Question 36

DBMS Components–Forms generator

Answer 36

creates screen forms for data input and display (sometimes an external component)

Question 37

DBMS Components–Report writer

Answer 37

creates designs for printed data reports (sometimes an external component