This chapter and the next cover some of the basic principles of
computer systems, including the basic architecture, terminology
and data representation. Computers use binary digits to represent
data, which, for humans, is not a very convenient method of representing
numbers and characters. Thus, the second chapter discusses the techniques
which can be used which allow humans to more easily interpret computer
data. This includes the usage of hexadecimal, which is an easily
interpreted method of representing binary digits, and ASCII, which
Operating Systems and Distributed Systems.
Chapters 3 to 6 cover the principles of operating systems and how
information and processing is distributed over networks. Operating
systems are important in that they allow users to easily interface
to computer hardware, without actually knowing how the system works.
For example, think about how difficult it would be to identify files
on a disk drive using their actual physical location on the disk.
To most people the logical layout of files within folders makes
much more sense than the actual physical organization of the files
on the disk.
Data Communications and Compression.
Chapters 7 and 8 introduce the techniques of transmitting data,
and illustrate compression methods for data. Either this compression
reduces the amount of storage space, or the amount of time/bandwidth
that data will take when transmitted over a communications channel.
In the past data has typically been sent in a continuous manner
(known as analogue communications), but modern communications focuses
on transmitting binary digits, 0's and 1's (known as digital communications).
Networking and the Internet.
Chapters 9 to 12 introduce the theory and practice of computers
that communicating over a network. This network might be a local
area network, where computers are physically connected to the same
network, or might be wide area communications over the Internet.
A key principle in understanding how computers communicate over
a network is the OSI model, which abstracts the transmission of
data, at different levels. For example, the OSI model allows someone
to view the communications between two computers as a series of
binary digits with a series of electrical or light pulses (physical
layer). The model also allows the communication to be viewed as
a collection of bits with information about the destination address
location (data link layer), and so on. Chapter 10 presents the main
types of networks, and The WWW site contains additional chapters
which focus on two of the most important network types: Ethernet
and ATM. Both have important concepts for the local transmission
of data and for the global transmission of data. Networking technologies
such as Ethernet and ATM only really provide a communications channel
for the reliable transmission of data. A communications protocols
is then required so that data can be properly addressed over a global
communications channel, and the data can also to be split up into
smaller data units, so that it can be transmitted over the channel.
These are some of the main functions of a networking protocol, which,
if it is standardized, allow two computers to communicate, no matter:
their computer architecture, their type; their operating system;
their network connection; and their physical location. The two most
important networking protocols are IP and TCP. The IP part allows
for a global network addressing structure (using an IP address),
and the TCP part allows data to be broken down into chunks, each
with its own sequence number, and unique identification of the application
that it is destined for. These protocols are covered in some detail
in Chapters 11 and 12, and are key in understanding the organization
and operation of the Internet.
Encryption and Security.
Chapters 13 and 14 discuss some of the main principles used in
securing the storage and transmission of data. Obviously no network
can ever been totally secure, but most network administrators will
try and protect data at different levels of abstraction, such as:
physically securing transmission systems; filtering the content;
and filtering based on the source and destination of the data. The
only truly reliable method of securing data, though, is encryption.
Chapter 13 discusses some of the main principles in encryption,
and focuses on public-key encryption, which is now the most widely
used encryption method. This method involves users generating two
electronic keys, one of these private and the other is distributed
to anyone who wants to send the user some encrypted data. Anyone
sending the user some encrypted data uses the user's public key
to encrypt the data; the only key that can then decrypt the data
is then the user's private key. It is an ingenious method, which
is used in many applications, such as in electronic commerce and
in data security.
Databases and Information.
Chapters 15 and 16 discuss some of the main principles of using
data to gather, process and store present data, such as the use
of agents to gather data, and databases to store it. Databases are
key components of modern computing, thus a solid understanding of
the way that they are designed and organized is essential for understanding
any systems which are based around a database. Databases are now
used in many disciplines, such as creating dynamic content for WWW
sites, storage of banking details, storage of data samples from
industrial plant, and so on.
Chapter 17 covers the processes involved in developing software.
This includes the principles of software programming, software design,
and structured analysis and design. There is a great variety of
software development principles, and programming languages, thus
this chapter focuses on the choices that are made in practical development.
The Internet and the WWW have obviously increased the requirement
for intercommunication between computers, thus Chapter 12 gives
a basic outline of a communications program over a network.
WWW, Electronic Mail and Multimedia.
Chapters 18 to 20 cover the basic principles of WWW development,
the usage of electronic mail, and multimedia.