Computers and Information Systems
Computers and Information Systems
1. Computer systems
1.1 Classification of computers
Computers come in several sizes from tiny to enormous, in both physical size and capacity.
The capacity of a computer refers to the volume of data that the computer can process. Based
on the physical size and capacity, computers fall into four types: microcomputers,
minicomputers, mainframe computers and supercomputers.
1.1.1 Microcomputers
The most widely used and the fastest-growing type of computer is the microcomputer. It
is so called because the whole CPU is built in only one single chip – the microprocessor.
Sometimes microcomputer is also called PC (personal computer) or home computer.
Although microcomputer is the smallest in terms of size and capacity. Its processing
speed and capacity could not be compared with minicomputers and mainframe
computers when it is first developed. But nowadays a microcomputer can replace a
mainframe computer manufactured ten years ago.
Microcomputers can be further divided into two types:
Desktop computers
Desktop computers are small enough to fit on top of a desk and yet are too big to carry
around.
Desktop computers
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Computers and Information Systems
Portable computers
Portable computers are microcomputers that are small and light enough to move easily
from one place to another. There are several types of portable computers: notebook
computers, sub-notebook computers, handheld PCs.
Notebook computer
Sub-notebook
computers
Handheld PC
Can you tell me the names of some PC manufacturers?
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1.1.2 Minicomputers
Minicomputers are larger in size and more powerful than microcomputers. They are
designed for multi-users and usually used by medium-size companies or departments of
large companies to do research or to monitor a particular manufacturing process. Usually
a minicomputer has a powerful CPU and several terminals which can access the CPU for
processing.
Minicomputer
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1.1.3 Mainframe computers
Mainframe computers are large computers occupying specially wired, air-conditioned
rooms. They are composed of a number of separate units and usually act as a server for a
network. Mainframe computers are typically used by large organized, business, banks,
universities and government agencies, to handle millions of transactions.
Mainframe computer
In early days of computing, only mainframe computers were available. Minicomputers
were developed since early 1960's and microcomputers were developed in mid 1970's.
1.1.4 Supercomputers
Supercomputers are the most powerful and expensive computers. They can process
billions of instructions per second. They are usually used in scientific research, weather
forecasting, space explorations, engineering design and military defense.
Supercomputer
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Computers and Information Systems
2. Computer network
2.1 The need for networking
Networking is the process of connecting computers that permits the transfer of data and programs
between them. Its tremendous benefits have been proved by the widely use of Internet.
2.2 Network types
Local area network (LAN)
A LAN is a collection of computers and peripherals located relatively close to each other and
connected by cables. It is generally confined to a small area such as a building or an office. For
example, the network inside the school is a LAN.
File server
Usually there is a central computer inside a LAN which is called a server. Each individual
computer on the network can have access to the files on the server. The other computers on the
network are always called workstations.
Wide area network (WAN)
Computers in different countries and cities around the world can be connected through wide area
networks. A WAN is usually a collection of LANs. For example, a bank has hundreds of branches
in different locations in a country. Each branch has its own LAN. All LANs are connected
together to form a WAN, hence a banking system. Furthermore, a banking system can be
connected to another banking system to form a larger network.
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Internet is the most famous and widely used WAN in the world. It connects thousands of
networks around the world.
Give some examples of networks you find in the daily life.
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2.3 Advantage of networking
Communication
With computer networks, people can talk to each other on computers, and send messages and
document files to others through e-mail. Messages are sent immediately and no paper is needed.
The message can be stored and duplicate copies can be sent to several destinations at the same
time.
Give some advantages of e-mail over traditional postal system.
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Computers and Information Systems
Sharing of hardware
Hardware devices such as laser printers and plotters can be shared by networking. So cost and
space can be saved and.
Data
Sharing of information
Many organizations such as banks, supermarkets, airline companies need to share information.
Networking makes it possible for them to access data kept in a database or even more than one
database. For example, when a customer buys an airline ticket from a travel agency, the database in
the server must be updated at once. Otherwise, there may be another customer buys the same
ticket at later time.
3. Information processing
3.1 Information and data
There are plenty of data around us in the daily life. For example, raw marks got in examination,
prices listed in a supermarket, telephone numbers of schoolmates.
Consider the following list of numbers:
31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
What does it tell us? Not a lot!
They may be
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the temperatures of 12 consecutive days.
the marks got by a student in twelve tests.
the weights (in kg) of 12 girls.
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Unless we specify what they are, they would remain just numbers and contain little meaning.
If we say that these numbers represent the weights of 12 girls in kilograms, we have changed our
numbers into data.
We can then add all the numbers together and divide the sum by 12. Then we get the average
weight of the students, i.e. 30.3 kg.
This new information about the weights of the students is produced as a result of data
processing.
So, we have the following definitions:
Data are recorded facts or raw figures.
Information contains interpreted data: data that have been processed into a form that is
meaningful and useful to the user.
Data processing is the transformation of data into information by means of a set of predefined
rules.
Data
Data Processing
Information
More examples:
Exam. raw marks
Data Processing
Readings from
electric meters
Data Processing
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Ave. marks,
positions
Electric bills
Computers and Information Systems
3.2 Concepts of data processing
3.2.1
EDP
Manual data processing means the operations are mainly processed manually. We can
find that some people still perform calculations by means of abacuses in some traditional
shops.
Electronic data processing (EDP) means that data are processed mainly by computers.
This kind of processing is a trend in our society.
Examples of EPD:
Payroll system
Point of sale system
Give some more examples of manual data processing systems and EDP systems.
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The following are operations usually involved in a data processing system (taking an
examination result processing system as example):
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Calculation – find the total mark, average mark of each student
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Searching – find the average mark of a particular student from all records of a class
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Sorting – arrange the records of a class in descending order of average mark in
order to find the positions in class of all students
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Deleting – delete the record of a left student
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Inserting – insert the record of a newly admitted student
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Updating –correct a wrongly entered mark
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Report generation – print examination report for each student
Write down some examples of operations in a library system
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Calculation ______________________________________________________
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Searching ________________________________________________________
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Sorting __________________________________________________________
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Deleting _________________________________________________________
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Inserting _________________________________________________________
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Updating ________________________________________________________
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Reporting generation ______________________________________________
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Computers and Information Systems
3.2.2
Data accuracy
The accuracy of data is essential in a data processing system. Although the system is
accurate and efficient. If the data inputting data is not correct, the output from the
system will not be correct and accurate. Think of an examination result processing
system. If the marks entered in the system are always incorrect. What will happen? A
good student may be repeated instead of promoted! This concept is sometimes called
garbage-in-garbage-out.
Data processing
system
3.3 Modes of operation
Data processing systems can be divided into two kinds:
Batch processing – All data are collected into a batch and then run as a group. There is a time
delay between the collection of data and output of result.
Examples: marking of exam. scripts, preparing electric bills
Real time processing – Data are processed as soon as they are received. The system produces an
immediate response.
Examples: Easy Pay System, concert tickets booking system
Which mode of operation should be used
for a washing machine? Why?
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