Chapter 1 Introduction

Question 1

What is hardware? What is software?

Answer 1

The hardware of a computer system consists of its physical components such as a circuit board, monitor, or keyboard. Computer software consists of the programs that are executed by the hardware and the data that those programs use. Hardware is tangible, whereas software is intangible. In order to be useful, hardware requires software and software requires hardware

Question 2

What are the two primary functions of an operating system?

Answer 2

The operating system provides a user interface and efficiently coordinates the use of resources such as main memory and the CPU.

Question 3

The music on a CD is created using a sampling rate of 44,000 measurements per second. Each measurement is stored as a number that
represents a specific voltage level. How many such numbers are used
to store a three-minute long song? How many such numbers does it
take to represent one hour of music?

Answer 3

It takes 7,200,000 numbers for a three-minute song (40,000 * 60 * 3) and 144,000,000 numbers for one hour of music (40,000 * 60 * 60)

Question 4

What happens to information when it is stored digitally?

Answer 4

The information is broken into pieces, and those pieces are represented
as numbers.

Question 5

How many unique items can be represented with the following?

a. 2 bits
b. 4 bits
c. 5 bits
d. 7 bits

Answer 5

In general, N bits can represent 2^N unique items. Therefore:

a. 2 bits can represent 4 items because 2^2 = 4.
b. 4 bits can represent 16 items because 2^4 = 16.
c. 5 bits can represent 32 items because 2^5 = 32.
d. 7 bits can represent 128 items because 2^7 = 128

Question 6

Suppose you want to represent each of the 50 states of the United
States using a unique permutation of bits. How many bits would be
needed to store each state representation? Why?

Answer 6

It would take 6 bits to represent each of the 50 states. Five bits is not
enough because 2^5 = 32 but six bits would be enough because 2^6 = 64.

Question 7

How many bytes are in each of the following?

a. 3 KB
b. 2 MB
c. 4 GB

Answer 7

A kilobyte (KB) is 2^10 = 1,024 bytes, a megabyte (MB) is 2^20 = 1,048,576
bytes, and a gigabyte (GB) is 2^30 = 1,073,741,824 bytes. Therefore:

a. 3 KB = 3 * 1,024 bytes = 3,072 bytes = approximately
3 thousand bytes

b. 2 MB = 2 * 1,048,576 bytes = 2,097,152 bytes =
approximately 2.1 million bytes

c. 4 GB = 4 * 1,073,741,824 bytes = 4,294,967,296 bytes = approximately 4.3 billion bytes

Question 8

How many bits are there in each of the following?

a. 8 bytes
b. 2 KB
c. 4 MB

Answer 8

There are eight bits in a byte. Therefore:

a. 8 bytes = 8 * 8 bits = 64 bits
b. 2 KB = 2 * 1,024 bytes = 2,048 bytes = 2,048 * 8 bits = 16,384 bits
c. 4 MB = 4 * 1,048,576 bytes = 4,194,304 bytes = 4,194,304 * 8 bits = 33,554,432 bits

Question 9

The music on a CD is created using a sampling rate of 44,000 measurements per second. Each measurement is stored as a number that
represents a specific voltage level. Suppose each of these numbers
requires two bytes of storage space. How many MB does it take to
represent one hour of music?

Answer 9

Under the stated conditions, one hour of music would require 288,000,000 bytes (40,000 * 60 * 60 * 2). Dividing this number by the number of bytes in a megabyte (1,048,576 bytes) gives approximately 275 MB. Note that a typical audio CD has a capacity of about 650 MB and can store about 70 minutes of music. This coincides with an actual sampling rate of 41,000 measurements per second, two bytes
of storage space per measurement, and the need to store two streams of music to produce a stereo effect.

Question 10

What are the two primary hardware components in a computer? How
do they interact?

Answer 10

The two primary hardware components are main memory and the CPU. Main memory holds the currently active programs and data. The CPU
retrieves individual program instructions from main memory, one at a time, and executes them

Question 11

What is a memory address?

Answer 11

A memory address is a number that uniquely identifies a particular memory location in which a value is stored.

Question 12

What does volatile mean? Which memory devices are volatile and
which are nonvolatile?

Answer 12

Main memory is volatile, which means the information that is stored in it will be lost if the power supply to the computer is turned off. Secondary memory devices are nonvolatile; therefore, the information
that is stored on them is retained even if the power goes off.

Question 13

Select the word from the following list that best matches each of the
following phrases:
controller, CPU, main, network card, peripheral, RAM, register,
ROM, secondary

a. Almost all devices in a computer system, other than the CPU and
the main memory, are categorized as this.
b. A device that coordinates the activities of a peripheral device.
c. Allows information to be sent and received.
d. This type of memory is usually volatile.
e. This type of memory is usually nonvolatile.
f. This term basically is interchangeable with the term “main memory.”
g. Where the fundamental processing of a computer takes place.

Answer 13

The word that best matches is

a. peripheral
b. controller
c. modem
d. main or RAM
e. secondary or ROM
f. RAM
g. CPU

Question 14

What is a file server?

Answer 14

A file server is a network computer that is dedicated to storing and providing programs and data that are needed by many network users.

Question 15

What is the total number of communication lines needed for a fully
connected point-to-point network of five computers? Six computers?

Answer 15

Counting the number of unique connections in Figure 1.16, there are 10 communication lines needed to fully connect a point-to-point network of five computers. Adding a sixth computer to the network will require
that it be connected to the original five, bringing the total to 15 communication lines.

Question 16

Describe a benefit of having computers on a network share a communication line. Describe a cost/drawback of sharing a communication line.

Answer 16

Having computers on a network share a communication line is cost effective because it cuts down on the number of connections needed and
it also makes it easier to add a new computer to the network. Sharing lines, however, can mean delays in communication if the network is busy

Question 17

What is the etymology of the word Internet?

Answer 17

The word Internet comes from the word internetworking, a concept related to wide-area networks (WANs). An internetwork connects one
network to another. The Internet is a WAN.

Question 18

The TCP/IP set of protocols describes communication rules for software that uses the Internet. What does TCP stand for? What does IP
stand for?

Answer 18

TCP stands for Transmission Control Protocol. IP stands for Internet Protocol. A protocol is a set of rules that govern how two things communicate.

Question 19

Explain the parts of the following URLs:

a. duke.csc.villanova.edu/jss/examples.html
b. java.sun.com/products/index.html

Answer 19

Breaking down the parts of each URL:

a. duke is the name of a computer within the csc
subdomain
(the Department of Computing Sciences) of the
villanova.edu
domain, which represents Villanova University. The
edu top-level
domain indicates that it is an educational
organization. This URL
is requesting a file called examples.html from
within a subdirectory called jss.
b. java is the name of a computer (Web server) at the
sun.com domain, which represents Sun
Microsystems, Inc. The com toplevel domain
indicates that it is a commercial business. This
URL is requesting a file called index.html from
within a subdirectory called products.

Question 20

When was the Java programming language developed? By whom?

When was it introduced to the public?

Answer 20

The Java programming language was developed in the early 1990s by James Gosling at Sun Microsystems. It was introduced to the public in 1995

Question 21

Where does processing begin in a Java application?

Answer 21

The processing of a Java application begins with the main method.

Question 22

What do you predict would be the result of the following line in a
Java program?

System.out.println(“Hello”); // prints hello

Answer 22

The characters “Hello” will be printed on the computer screen.

Question 23

Which of the following are not valid Java identifiers? Why?

a. RESULT
b. result
c. 12345
d. x12345y
e. black&white
f. answer_7

Answer 23

All of the identifiers shown are valid except 12345 (since an identifier cannot begin with a digit) and black&white (since an identifier cannot contain the character &). The identifiers RESULT and result are both valid, but should not be used together in a program because they differ only by case. The underscore character (as in answer_7) is a valid part of an identifier.

Question 24

Suppose a program requires an identifier to represent the sum of the
test scores of a class of students. For each of the following names,
state whether or not each is a good name to use for the identifier.
Explain your answers.

a. x
b. scoreSum
c. sumOfTheTestScoresOfTheStudents
d. smTstScr

Answer 24

Although any of the listed names could be used as the required identifier, the only “good” choice is scoreSum. The identifier x is not descriptive and is meaningless, the identifier sumOfTheTestScoresOfTheStudents is
unnecessarily long, and the identifier smTstScr is unclear.

Question 25

What is white space? How does it affect program execution? How
does it affect program readability?

Answer 25

White space is a term that refers to the spaces, tabs, and newline characters that separate words and symbols in a program. The compiler ignores extra white space; therefore, it doesn’t affect execution. However, it is crucial to use white space appropriately to make a program readable to humans

Question 26

We all know that computers are used to perform complex jobs. In this
section, you learned that a computer’s instructions can do only simple
tasks. Explain this apparent contradiction

Answer 26

At the lowest level, a computer’s instructions perform only simple tasks, such as copying a value or comparing two numbers. However, by putting together millions of these simple instructions every second, a computer can perform complex tasks.

Question 27

What is the relationship between a high-level language and a machine
language?

Answer 27

High-level languages allow a programmer to express a series of program instructions in English-like terms that are relatively easy to read and use. However, in order to execute, a program must be expressed in a particular computer’s machine language, which consists of a series of bits that are basically unreadable by humans. A high-level language program must
be translated into machine language before it can be run.

Question 28

What is Java bytecode?

Answer 28

Java bytecode is a low-level representation of a Java source code program. The Java compiler translates the source code into bytecode, which can then be executed using the Java interpreter. The bytecode might be transported across the Web before being executed by a Java interpreter that is part of a Web browser.

Question 29

Select the word from the following list that best matches each of the
following phrases:
assembly, compiler, high-level, IDE, interpreter, Java, low-level, machine

a. A program written in this type of language can run directly on a
computer.
b. Generally, each language instruction in this type of language
corresponds to an equivalent machine language instruction.
c. Most programmers write their programs using this type of
language.
d. Java is an example of this type of language.
e. This type of program translates code in one language to code in
another language.
f. This type of program interweaves the translation of code and the
execution of the code.

Answer 29

The word that best matches is

a. machine
b. assembly
c. high-level
d. high-level
e. compiler
f. interpreter

Question 30

What do we mean by the syntax and semantics of a programming

language?

Answer 30

Syntax rules define how the symbols and words of a programming language can be put together. The semantics of a programming language instruction determine what will happen when that instruction is
executed.

Question 31

Categorize each of the following situations as a compile-time error,
run-time error, or logical error.

a. Misspelling a Java reserved word.
b. Calculating the average of an empty list of numbers by dividing
the sum of the numbers on the list (which is zero) by the size of
the list (which is also zero).
c. Printing a student’s high test grade when the student’s average test
grade should have been output.

Answer 31

a. Compile-time error
b. Run-time error (you cannot divide by zero)
c. Logical error

Question 32

List the five general steps required to solve a problem

Answer 32

1. Understand the problem.
2. Design a solution.
3. Consider alternatives and refinements to the solution.
4. Implement the solution.
5. Test the solution

Question 33

Why is it important to consider more than one approach to solving a
problem? Why is it important to consider alternatives early in the
process of solving a problem?

Answer 33

The first solution to a problem that we think of may not be a good one. By considering alternative solutions before expending too much energy implementing our first idea, we can often save overall time and effort.

Question 34

What are the primary concepts that support object-oriented

programming?

Answer 34

The primary elements that support object-oriented programming are objects, classes, encapsulation, and inheritance. An object is defined by a class, which contains methods that define the operations on those
objects (the services that they perform). Objects are encapsulated such that they store and manage their own data. Inheritance is a reuse technique in which one class can be derived from another.

Question 35

What do you predict would be the result of the following line in a
Java program?
// prints hello System.out.println("Hello");

Answer 35

The entire line of code is a comment, so there is no result.