Computer Studies
Form 5
Syllabus 2013
Form 5 Computer Studies Notes
TABLE OF CONTENTS
2.4 TRANSLATION OF HIGH-LEVEL LANGUAGES ............................... 6
2.4.1 Higher Level Languages, Translators, Source and Executable Code .........6
4.6 LANGUAGE TRANSLATORS.................................................................. 9
4.6.1 The difference between compilers, interpreters and assemblers – the
relative advantages (and disadvantages) of each. ..........................................................9
Assembler .............................................................................................................................................9
Compiler ..............................................................................................................................................10
Interpreter .........................................................................................................................................11
Which to use – Compiler or Interpreter? .........................................................................11
4.6.2 Source code and Executable Code ...............................................................................12
4.6.4 4GL ..................................................................................................................................................13
4.6.5. Software Portability ............................................................................................................15
2.3 THE CPU ................................................................................................... 16
2.3.14 Typical machine code instructions - load, store and process (e.g. Add,
sub etc.) instructions. ......................................................................................................................16
Moving of Data.................................................................................................................................17
Computing ..........................................................................................................................................18
Affecting the Program Flow .....................................................................................................19
2.3.15 Using mnemonics to represent machine instructions. ..................................19
2.3.16 Symbolic addressing. ........................................................................................................21
2.3.17 Conditional and unconditional branches ...............................................................23
Unconditional Jump ......................................................................................................................24
Conditional Branching .................................................................................................................24
2.5 THE OPERATING SYSTEM .................................................................. 27
2.5.1 System software; Resource management functions of OS ...........................27
Process Management ...................................................................................................................27
Memory Management ..................................................................................................................28
Disk Management (File Systems) .........................................................................................29
Networking ........................................................................................................................................29
Security ................................................................................................................................................30
GUI (Graphical User Interface) .............................................................................................31
Device Drivers ..................................................................................................................................33
Mr.A.Gatt
Page 2 of 88
Form 5 Computer Studies Notes
3.5 TYPES OF OPERATING SYSTEMS .................................................... 34
3.5.1 Real time OS..............................................................................................................................34
3.5.2 Batch OS ......................................................................................................................................36
3.5.3 Time sharing OS ......................................................................................................................37
3.5.4 The necessity of different OS's to support different modes and
configurations. .....................................................................................................................................38
Real-Time Operating System ..................................................................................................39
Batch Operating System ............................................................................................................39
Time Sharing Operating System ...........................................................................................40
3.5.5 Common types of operating systems – single-user, multiuser,
networked, single programming, multi programming. ................................................40
2.8 DEDICATED COMPUTER SYSTEMS.................................................. 42
2.8.1 Difference between a general-purpose and a dedicated computer. ........42
2.8.2 Embedded and process control systems. .................................................................42
2.8.3 Computerised appliances as an example of dedicated systems – VCR,
auto pilot, mobile phones, GPS, etc. .......................................................................................43
2.8.4 Specialised I/O devices (sensors, buttons, LCD). ..............................................44
2.8.5 Software for dedicated computer systems .............................................................47
3.4 NETWORKS ............................................................................................. 48
3.4.1 Networking LAN and WAN ................................................................................................48
3.4.2 Advantages of a LAN ............................................................................................................49
3.4.3 Use of modems ........................................................................................................................50
3.4.4 Use of WANS for email, WWW, Video Conferencing .........................................52
E-Mail (Electronic Mail) ..............................................................................................................53
WWW (World Wide Web) ..........................................................................................................55
Video Conferencing .......................................................................................................................57
3.4.5 Server and client machines; the problem of bandwidth at a general
level. ...........................................................................................................................................................57
Network Topology .........................................................................................................................59
Bus Network .................................................................................................................................59
Ring Network ...............................................................................................................................60
Star Network ................................................................................................................................61
5.3 DATA SECURITY AND PRIVACY ...................................................... 62
Mr.A.Gatt
Page 3 of 88
Form 5 Computer Studies Notes
5.3.1 Need of data security and integrity of data. ..........................................................62
5.3.2 Backups (the generations of files: grandfather, father, son files), .........62
5.3.3 Physical security and software safeguards. ..........................................................64
Physical Security ............................................................................................................................64
Software Security ..........................................................................................................................65
IDS (Intrusion Detection System) ..................................................................................65
User ID (User Identification) .............................................................................................65
Biometric ........................................................................................................................................66
Encryption .....................................................................................................................................66
Digital Signature ........................................................................................................................67
Digital Certificate ......................................................................................................................67
5.3.4 Software piracy and copyright. .....................................................................................68
Copyright ............................................................................................................................................69
5.3.5 Ethical and legal issues. .....................................................................................................70
Ethical Issues ...................................................................................................................................70
Legal Issues ......................................................................................................................................72
5.3.6 Hardware and software procedures which deter piracy - serial
numbers and activation keys, hardware keys (dongles). ..........................................73
5.3.7 Software registration. .........................................................................................................74
5.3.8 Access rights. Privacy on multi-user/network systems. ................................74
5.2 EFFECTS OF COMPUTER-BASED SYSTEMS ON INDIVIDUALS,
ORGANISATIONS AND SOCIETY ............................................................ 76
5.2.1 Positive and negative effects of computerisation ..............................................76
Computers and Work ...................................................................................................................76
Computers and the Workplace ...............................................................................................77
Computers and Society (involving the Internet) ........................................................77
Computers and the Individual ................................................................................................78
5.4 MULTIMEDIA .......................................................................................... 79
5.4.1 Brief overview of capabilities and trends................................................................79
Interactive Video ...........................................................................................................................79
Browse .................................................................................................................................................80
Video Clip ............................................................................................................................................80
Video Data Compression ............................................................................................................80
5.4.2 Future perspectives (home office, access to public and institutional
databases, libraries, high-quality sound and pictorial data representation). 81
5.4.3 Basic hardware and software requirements and costs. ..................................83
3.2 ROLES RELATED TO AN I.T. ENVIRONMENT .............................. 84
Mr.A.Gatt
Page 4 of 88
Form 5 Computer Studies Notes
3.2.1 Information Systems Manager.......................................................................................84
3.2.2 Systems Analyst/Designer ...............................................................................................84
3.2.3 Systems Administrator .......................................................................................................85
3.2.4 Programmer ..............................................................................................................................86
3.2.5 I.T. Trainer .................................................................................................................................86
3.2.6 Operator ......................................................................................................................................87
3.2.7 Data Clerk ...................................................................................................................................87
3.2.8 Web Master ................................................................................................................................87
3.2.9 Lab technician ..........................................................................................................................88
3.2.10 Maintenance engineer ......................................................................................................88
Mr.A.Gatt
Page 5 of 88
Form 5 Computer Studies Notes
2.4 Translation of High-Level Languages
2.4.1 Higher Level Languages, Translators, Source and Executable
Code
Machine code is the closest language to the computer system. When
coding in machine code, only binary can be used; therefore everything
has to be coded in 1s and 0s. So, a programming statement in
machine code could be something similar to this:
0
0
0
Op-code
1
0
0
0
0
1
0
0
0
Operand or Address
In this case the first four bits of the statement are op-codes (which
determine the function that must be worked out), and the second part
– the operand reflects the data which is passed on to the function; or
in certain cases an operand might be replaced by a memory location
(address).
The combination of bits in the op-code section refers to a special
function; for example: the combination 0001 represents ADD, 0002
represents MUL, etc… In the above example, since there are four bits
assigned to the op-code section, there can be a total of 24=16 different
functions.
When assembly language is used, mnemonics are used instead of the
actual machine code. So instead of coding 0001|00001000 we can use
Mr.A.Gatt
Page 6 of 88
Form 5 Computer Studies Notes
ADD 8. However, since this is not machine code, we have to convert it
using a special application called an assembler. An assembler
converts the mnemonics and the relative operands and/or addresses
to machine code. This is the case also for all other high-level
languages; when a program is not coded in machine code, the highlevel coding has to be converted into machine code. In the case of
high-level languages compilers and interpreters are used.
High-level languages were developed with the primary aim of ease of
use for the user. Whilst a machine code program is executed very fast
on a computer, its coding can be a very difficult process for the
programmer because everything has to be coded in binary. Also, a
simple task (such as adding two numbers) that might require various
lines in a low-level language (such as Assembly) can be worked out in
fewer lines using a high-level language (such as Pascal); this is shown
in the following example:
The task is to add two numbers (6 and 9) and display their total.
Assembly
Language
Pascal
MOV AX, #6
MOV BX, #9
ADD AX, BX
PUSH AX
CALL WRITE
WRITE(6+9);
Figure 1 : Assembly vs. Pascal
Mr.A.Gatt
Page 7 of 88
Form 5 Computer Studies Notes
4.6 Language Translators
4.6.1 The difference between compilers, interpreters and assemblers –
the relative advantages (and disadvantages) of each.
Computers can only understand machine code (1GL), so in order to
convert all other generation of languages, a translator is required.
This translator is required to change the source code (code created by
the user) into executable code (code that the computer is able to
understand).
Source
Code
Translator
Executable
Figure 2: Source Code into Executable
However, there is the need for more than one type of translator:

Assembler: This is used to convert assembly language into
machine code.

Compiler & Interpreter: These are both used to convert higher
generation languages into machine code.
Assembler
The assembler is used to convert Assembly code into machine code.
Assemblers are usually very fast to convert the source code into
executable code because assembly is very close to the computer
language.
Mr.A.Gatt
Page 9 of 88
Form 5 Computer Studies Notes
The main duties of the assembler are to:

Translate each source code instruction into machine code

Place program instructions into memory locations

Assign the required address

Hand over the execution of the program to the Control Unit
The above duties are a general outline of the duties of an assembler,
because these might vary between different assemblers and different
CPUs.
Compiler
A compiler is used to convert a high-level language program into an
executable file. A compiler is dedicated only to one programming
language; i.e. a compiler that works for Pascal will not work for C.
Also, compilers vary from architecture to another, i.e. a compiler of
C++ for a PC will not be the same as a compiler of C++ for Macintosh.
The compiler‟s task is to translate the source code into executable
code. This is done by translating the existing code at one go. During
this translation process the compiler checks the syntax of the
program to make sure that the program is well-coded (no errors) and
that the program makes use of existing reserved words.
After the program is thoroughly checked, all libraries used (such as the
CRT library in Pascal) are linked, and the program is converted into
machine code, which in turn is passed on to the control unit so that
the program is executed.
Mr.A.Gatt
Page 10 of 88
Form 5 Computer Studies Notes
Interpreter
Interpreter has the same functions of a compiler, but the difference is
that Interpreter checks each statement as it is being typed in. When
using a compiler like Pascal‟s, first the whole program is coded, and
then the program is compiled all lines at one go, and in the case of any
errors, the programmer will be informed. When using Basic (which
uses an interpreter), as soon as a statement is coded, and the Enter
button is pressed, the interpreter will inform the programmer of any
errors found in that line. So, an interpreter changes the source code
into machine go, as it is being typed.
Which to use – Compiler or Interpreter?
The choice between a compiler and interpreter depends on the
scenario. If a program is being developed and requires testing,
interpreter is ideal, because it highlights the mistakes as the
programmer goes along. However, once the program has been fully
coded and tested, it is more feasible to use a compiler because it is
faster than an interpreter.
Summary of Differences between Assembler, Compiler and Interpreter
Assembler
Compiler
Interpreter
Can only be used for 2GL
Must be used for higher
Must be used for higher
code.
generation languages.
generation languages.
Assemble the source code
Compiles the source code
Interprets the source code
all at once.
all at once.
one line at a time.
Errors are very difficult to
Errors are more difficult to
Errors are easy to find and
find.
find.
correct.
Very fast execution.
Very fast execution.
Slow execution.
Example: Assembly
Example: Pascal
Example: Basic
Figure 3: Language Translators Choice
Mr.A.Gatt
Page 11 of 88
Form 5 Computer Studies Notes
4.6.2 Source code and Executable Code
Source code is the code as typed in by the programmer. The structure
and syntax of the source code depends on the programming language
used. The following code illustrates a function which adds up two
numbers. The first example is in PASCAL and the second in C++.
PASCAL
Function AddNums(n1 : integer, n2: integer):integer;
Begin
AddNums:=n1+n2;
End;
C++
int AddNums (int n1, int n2)
{
return n1+n2;
}
As you can see from the above code statements, in order to carry out
the same thing, different structures are used for different languages. A
computer does not understand any of these languages unless it uses a
translator
(interpreter
or
compiler).
So,
all
these
English-like
statements must be converted into machine code (1s and 0s) so that it
can be understood by the computer. Once these have been compiled,
these applications can run without the need for these translators, so in
turn we have the executable file, which under the Windows operating
system has an EXE extension.
Mr.A.Gatt
Page 12 of 88
Form 5 Computer Studies Notes
If one tries to open the EXE files using the same programming
language‟s editor, one will find that the program is not the same (and
it is unreadable). This happens because after the source code has been
compiled into an executable, the executable file is in the computer‟s
language (machine code).
4.6.4 4GL
A Fourth generation language (4GL) is a computer language that is
more advanced than traditional high-level programming languages.
For example, in dBASE (a 4GL created for databases), the command
List displays all the records in a data file. In second- and thirdgeneration languages, in order to read all records in a data file a
number of steps must be carried out, such as:

Read a record

Test if it is the end of the file

If it is not the end of the file display the record on screen, and
go back to the start

If it is the end of the file, stop program.
First-generation languages are machine languages; second-generation
are
machine-dependent
assembly
languages;
third-generation
languages are high-level programming languages, such as FORTRAN,
COBOL, BASIC, Pascal, and C.
Although many languages are called fourth-generation languages, they
are actually a mix of third and fourth. For example, the List command
in
dBASE
is
a
fourth-generation
command,
but
applications
programmed in dBASE are third-generation.
Mr.A.Gatt
Page 13 of 88
Form 5 Computer Studies Notes
The following command examples show the difference between third
and fourth-generation syntax to open a customer file and display all
names and addresses on screen.
dBASE 3GL
dBASE 4GL
use customer
use customer
do while .not. eof()
list name, address
? name, address
skip
enddo
Figure 4: 3GL vs 4GL
Query language (SQL) and report writers are also fourth-generation
languages. Any computer language with English-like commands that
does not require traditional input-process-output logic falls into this
category.
Many fourth-generation language functions are also built into graphical
interfaces and activated by clicking and dragging. The commands are
embedded into menus and buttons that are selected in an appropriate
sequence.1
1
Source: http://www.answers.com/topic/fourth-generation-programming-language
Mr.A.Gatt
Page 14 of 88
Form 5 Computer Studies Notes
4.6.5. Software Portability
When using low-level languages, it is very difficult to make a program
that was created on a computer to work on another type of computer
that has a different CPU and/or hardware devices. So, clearly the
biggest benefit of high-level languages is that it can run on various
machines provided that there is the required translator.
When using assembly language, the coding required to perform a
particular task may vary from one computer to another. Hence, a
program coded on a Pentium 3 processor will probably not work on an
Athlon processor (and the other way round). But, by using a high-level
language the program can be translated to the computer‟s language
and therefore can run on different machines. This is known as
Software Portability.
The best example of software portability is JAVA. After a program has
been coded in JAVA, it is not compiled immediately, but it is compiled
only when it is needed. This makes it possible that a JAVA program
runs on different platforms (different operating systems and/or CPUs)
without any problems, since the program is compiled accordingly.
Mr.A.Gatt
Page 15 of 88
Form 5 Computer Studies Notes
2.3 The CPU
2.3.14 Typical machine code instructions - load, store and process
(e.g. Add, sub etc.) instructions.
The Assembly language is made up of op-codes (mnemonics) and
operands. These op-codes can be compared to reserved words in a
higher-level programming language - like the reserved words Readln,
Writeln, Repeat…Until in Pascal.
2
Instructions in assembly language are generally very simple, unlike in
a high-level language. Any instruction that references memory (either
for to store or retrieve data, or as a jump target) will also have an
addressing mode to determine how to calculate the required memory
address. More complex operations are then built on the concept of
these simple operations.
2
Source: http://en.wikipedia.org/wiki/Assembly_language#Machine_instructions
Mr.A.Gatt
Page 16 of 88
Form 5 Computer Studies Notes
Some operations available in most instruction sets include:
Moving of Data
Set
temporary STO 10
This will store a result (found in
location in the CPU itself) to a
the accumulator) to a memory
fixed constant value.
location, which in this case is 10.
Move
a
register
data
(a
from
a
memory mov ah, 09
location to a register, or vice This will move the constant
versa. This is done to obtain the number 9 to the register ah.
data to perform a computation on
it later, or to store the result of a
computation.
Read
and
write
hardware devices
data
from INP ah, 145
Receives input
from
the
input
device with the code 145 and
stores it into register ah.
Mr.A.Gatt
Page 17 of 88
Form 5 Computer Studies Notes
Computing
Add, subtract, multiply, or divide ADD AX, BX
Add the contents found in the
the values of two registers,
register AX with the contents in
placing the result in a register
register BX and store the result in
register AX.
Perform bitwise operations, taking OR AX, BX
Executes an bit-wise OR between
the conjunction / disjunction
the two registers and stores the
(and/or) of corresponding bits in a
result in BX.
pair of registers, or the negation
(not) of each bit in a register
Compare two values in registers CMP AX, BX
Compares
the
values
by
(for example, to see if one is less,
subtracting the BX from AX, the
or if they are equal)
result is not stored.
Mr.A.Gatt
Page 18 of 88
Form 5 Computer Studies Notes
Affecting the Program Flow
Jump to another location in the JMP dest
This will force the flow of the
program and execute instructions
program
to
jump
to
the
there
destination
specified
as
an
argument.
Jump to another location if a JNZ dest
This will jump to the destination if
certain condition holds
the accumulator is not Zero.
For more info:
http://en.wikibooks.org/wiki/X86_Assembly/X86_Instructions
2.3.15 Using mnemonics to represent machine instructions.
As already mentioned in previous sections, coding in binary is a very
difficult and time-consuming process, hence assembly was created.
So, instead of coding in binary numbers, mnemonics are used.
Mnemonics are short words (usually made up of 3 characters) which
when invoked, perform a function. These mnemonics are much easier
to remember by programmers, since their make-up usually refers to
what they will perform, for example:
Mr.A.Gatt
Page 19 of 88
Form 5 Computer Studies Notes
Op.code
(binary)
Mnemonic Function
LoaD
Accumulator
with
contents
of
specified
0000
LDA
address.
0001
STA
STore Accumulator contents in specified address.
ADD contents of the specified address to the
0010
ADD
accumulator.
SUBtract contents of specified address from the
0010
SUB
accumulator.
0110
JPU
JumP Unconditionally to the specified address
Jumps to the specified address if Accumulator is
0111
JAZ
Zero.
1001
JAL
Jumps to specified address if Accumulator < zero.
Jumps to the specified address if the Accumulator
1010
JAG
> zero.
1111
HLT
Stop the program
As you can see from the above mnemonics it is much easier to
remember their function rather than to remember a numeric (binary)
code.
For more information on the Assembly Language:
http://www.osdata.com/topic/language/asm/asmintro.htm
Mr.A.Gatt
Page 20 of 88
Form 5 Computer Studies Notes
2.3.16 Symbolic addressing.
In Assembly language, there are two ways in which the computer can
find locations from memory; these are Absolute Addressing and
Relative Addressing.
Absolute Addressing: During the execution of an assembly program
various memory locations must be used to manage data. In certain
cases, the memory location to be used can be specified by giving the
actual memory location. For example, the assembly command LDA 10
is specifying that the accumulator should be filled with the contents
found in memory location (in the address) 10. Hence, in this case we
are referring to the exact location in memory.
9
10
11
12
13
LDA 10
Figure 5: Example of Absolute Addressing
Mr.A.Gatt
Page 21 of 88
Form 5 Computer Studies Notes
Relative Addressing: This is indicated by specifying the distance from
another address which in this case is called the base address. So, in
this case the exact memory location is not given. For example, the
assembly command MOV CX, [BX+4] is specifying that the contents of
Register C must be moved in the location which is found 4 locations off
register B.
Bx
Bx+
1
MOV CX,[BX+4]
Bx+
2
Bx+
3
Bx+
4
Note:
BX is the base address
Figure 6: Example of Relative Addressing
Symbolic Addressing: In assembly programming a label can be given
to a memory location. So, instead of referring to the memory location
by the location itself (i.e. the location number) a label is used. So, if
for example the memory location 106 can be assigned a label Num1,
and from then on, whenever location 106 is required, instead of calling
memory location 106, Num1 is called – LDA Num1.
Mr.A.Gatt
Page 22 of 88
Form 5 Computer Studies Notes
103
104
105
106
107
NUM1
LDA NUM1
Figure 7: Symbolic Addressing
2.3.17 Conditional and unconditional branches
The program counter (PC) found in the CPU always points to the next
instruction which must be fetched. By changing the program counter,
instructions can be executed in a different order rather than in a
sequential manner.
3
In order to jump instructions, labels must be used; labels are
essential for branching. Labels can be created by simply specifying a
label name and adding a colon at the end of the label. For example:
label1:
mov ax,5
mov bx,3
3
Adapted from: http://www.geocities.com/SiliconValley/Park/3230/x86asm/asml1006.html
Mr.A.Gatt
Page 23 of 88
Form 5 Computer Studies Notes
Unconditional Jump
This type of branching instructs the processor to jump to a label
without any conditions. The command for this type of jump is JMP. The
following illustrates an example of an unconditional jump.
When the JMP command is
encountered, the flow of the
program will resume from the
specified label; in this case lab1.
mov ax, 5
jmp lab1
add ax, 4
lda 10
lab1: sub ax, 3
In the above program, as soon as the command jmp
lab1 is
encountered, the program will jump to and continue from the label.
Hence, the commands add ax,4 and lda 10 will be skipped, and sub
ax,3 will be worked next. As already mentioned, an unconditional
branch does not have any conditions, so when the jump command is
encountered it will simply skip to the label.
Conditional Branching
Conditional branching allows the program to skip to another location
(through the use of labels) but only if it satisfies a condition. In order
to use this type of branching however, a comparison must be done
first. So, first we carry out the comparison, and then we jump to a
label if the comparison satisfies the jump‟s criteria. The following
example illustrates a conditional jump, and the equivalent in Pascal is
listed as well.
Mr.A.Gatt
Page 24 of 88
Form 5 Computer Studies Notes
Assembly
PASCAL
cmp ax, bx
if ax > bx then
jg isgreater
begin
:
; block 1 (else part)
… {block 2}
jmp after
end else
isgreater:
begin
:
; block 2 (then part)
… {block 1}
after:
end
:
{after if}
; after if
So by looking at the above assembly program, the registers ax and bx
are compared with each other using the command CMP. Then the
command jg (jump if greater) is used to jump to the label isgreater
if ax is greater than bx, otherwise it will jump to label after. The
actual comparison is carried out using the CMP command, and then
different jump statements can be used. The following table illustrates
different types of jumps:
Instruction
Meaning
jg
Jump if greater
jge
Jump if greater or equal
jl
Jump if less
jle
Jump if less or equal
je
Jump if equal
jne
Jump if not equal
jc
Jump if carry flag is set
Figure 8: Different types of Jumps
Mr.A.Gatt
Page 25 of 88
Form 5 Computer Studies Notes
The following flowcharts illustrate the three different types of
executions which are Sequential, Unconditional and Conditional
execution.
Sequential
Unconditional
i=0
i=0
Conditional
i=0
A
A
Print i
Print i
Print i
i=i+1
i=i+1
i=i+1
Print
“Done”
Goto A
y
Print
“Done”
i<
10
n
Print
“Done”
Figure 9: Different types of Executions
For more information:
http://homepages.ius.edu/jfdoyle/c335/Html/Chapter4.htm#Execution
%20Control
Mr.A.Gatt
Page 26 of 88
Form 5 Computer Studies Notes
2.5 The Operating System
2.5.1 System software; Resource management functions of OS
The operating system (also known as system software) is essential for
any computer to work; every computer system must have an
operating system (OS) in order for other application software and/or
hardware to work. There are various tasks which are carried out by the
OS as depicted in the diagram below:
Process
Management
GUI
(Graphical
User Interface)
Memory
Management
Operating
System
Disk
Management
(File Systems)
Device
Drivers
Security
Networking
Figure 10: Tasks of an O/S
Process Management
Mr.A.Gatt
Page 27 of 88
Form 5 Computer Studies Notes
Every application that runs on the computer system is run inside a
process which is executed by the CPU. Due to the current architecture
of the CPU, only one process at a time can be executed. However,
many modern operating systems allow many processes to “run at the
same time”; this is achieved by switching from one process to another
very quickly – this is called Multitasking.
Multitasking allows the CPU to run more than one process at the same
time by giving each process attention for a very brief period of time
(timeshare), before moving on to the next process. However, if there
are many concurrent processes problems may arise because since the
CPU has to cater for many processes, some processes might not get
the attention they require, and the application will not work correctly.
So, process management involves the computation and distribution of
"timeshares".
Memory Management
The computer has different type of memories which it can use, and
these are arranged in a hierarchical manner, starting from the fastest
being the memory registers, cache, RAM and ending in disk storage.
The purpose of the OS's memory management is to track which
memory is free, which memory is to be allocated and deallocated, and
how to swap between the main memory and secondary memory.
Swapping
data
between
memories
is
called
virtual
memory
management – this allows some dedicated hard-disk space to act as
RAM if the actual RAM is not sufficient. However, this virtual RAM is
Mr.A.Gatt
Page 28 of 88
Form 5 Computer Studies Notes
not as fast as RAM and excessive use may result in computer
thrashing.
Disk Management (File Systems)
Operating systems have a variety of native file systems. Linux has a
greater range of native file systems, the most common being: ext2,
ext3, ReiserFS. Windows on the other hand has a file system support
which includes: FAT16, FAT32, and NTFS. The NTFS file system is the
most efficient and reliable of the three Windows systems. All the FAT
systems are older than NTFS and have limitations on the partition and
file size.
For most of the above file systems there are two ways it can be
allocated. Each system can be journaled or non-journaled. Journaled is
the safer alternative under the circumstances of a system recovery, if
a system comes to an abrupt stop (a system crash), the non-journaled
system will need to undergo an examination from the system check
utilities where as the journaled file systems recovery is automatic.
Microsoft's NTFS is journaled along with most Linux file systems,
except ext2, but including ext3, ReiserFS.
Every file system is made up of similar directories and subdirectories.
Along with the operating systems file system similarities there are the
subtle differences. Microsoft separates its directories with a back-slash
„\‟ and its file names aren't case sensitive whereas Unix-derived
operating systems (including Linux) use the forward-slash „/‟ and their
file names generally are case sensitive.4
Networking
4
Adapted from http://en.wikipedia.org/wiki/Operating_system#Disk_and_file_systems
Mr.A.Gatt
Page 29 of 88
Form 5 Computer Studies Notes
Most of the operating systems nowadays are capable of using the now
universal TCP/IP (Transmission Control Protocol/Internet Protocol)
protocol. This allows computers to communicate with each other and
be able to share resources such as files and hardware devices.5
Security
The basic type of security pertaining to an operating system is the
ability to authenticate users before using the operating system; this is
performed by the use of a username and password. Generally, only
permitted users are allowed to log in the system, but level access is
also implemented.
Level access limits the things a particular user can perform on the
operating system; these levels are usually implemented by the system
administrator and are called system policies.
Another type of security of an operating system is network related.
The task of protecting the computer from network breaches is carried
out using a firewall. Basically, when using the TCP/IP protocol, the
operating system assigns various ports to different services (such as
web-browsing, e-mailing, file sharing, etc). The firewall closes unused
or dangerous ports, and limits the traffic to and fro the computer.
5
Adapted from http://en.wikipedia.org/wiki/Operating_systems#Networking
Mr.A.Gatt
Page 30 of 88
Form 5 Computer Studies Notes
GUI (Graphical User Interface)
Nowadays, most operating systems use a GUI, which is more userfriendly since it uses graphical representations which the user can
simply manipulate using the mouse. Some of the GUI's components
include icons, menus, windows, toolbars and buttons amongst others.
Each operating system uses different GUIs, for example Windows uses
a different GUI than MacOS or Linux.
Figure 11: MacOSX
Mr.A.Gatt
Page 31 of 88
Form 5 Computer Studies Notes
Figure 12: Linux OS
Figure 13: Windows XP OS
Mr.A.Gatt
Page 32 of 88
Form 5 Computer Studies Notes
Device Drivers
A device driver is a specific type of computer software developed to
allow interaction with hardware devices. Typically a device driver
creates an interface for communicating with the device, through the
specific computer bus or communications subsystem that the hardware
is connected to, providing commands to and/or receiving data from
the device, and on the other end, the requisite interfaces to the
operating system and software applications.
Every model of hardware (even within the same class of device) is
different. Newer models also are released by manufacturers that
provide more reliable or better performance and these newer models
are often controlled differently. Computers and their operating systems
cannot be expected to know how to control every device, both now
and in the future. To solve this problem, OSes essentially dictate how
every type of device should be controlled. The function of the device
driver is to translate these OS created function calls into device
specific calls.
In theory a new device, which is controlled in a new manner, should
function correctly if a suitable driver is available. This new driver will
ensure that the device appears to operate as usual from the operating
systems' point of view.6
6
Adapted from http://en.wikipedia.org/wiki/Operating_systems#Device_drivers
Mr.A.Gatt
Page 33 of 88
Form 5 Computer Studies Notes
3.5 Types of Operating Systems
Operating systems have been developed to cater for different
computing scenarios. The same type of operating system is not
capable of handling all the different requirements that will arise in
different cases.
3.5.1 Real time OS
A real-time operating system (RTOS) is designed to immediately
deliver the results for an activity or an event that is happening in realtime. This means that once the inputs have been submitted, the
output must be immediate.
An example for the need of a
real-time operating system is
on a Fighter Jet. On modern
aircrafts computers play a vital
role in keeping the aircraft
flying. Due to the very delicate
and critical moments in flying such a high-velocity aircraft, every
command issued by the pilot must be acted upon immediately, and not
left waiting because that might lead to catastrophic results.
Mr.A.Gatt
Page 34 of 88
Form 5 Computer Studies Notes
There are two main types of real-time operating system:

“Hard” Real-Time: In this case, if the operating system fails to
finish off a calculation by the time it was required, the whole
process will fail. This happens because then the next calculations
will not be able to be worked out since they were dependent on
the unfinished calculation.

“Soft” Real-Time: The main difference from “Hard” real-time is
that consecutive calculations will still be able to be worked out,
but usually at a less efficient pace since the previous calculations
were not finished off by their designated time.
An operating-system can be considered to be real-time if it is or has:

Multitasking: it can perform more than one task at a time.

Priority of Process: some processes can be deemed to be
more important than others and hence worked out before less
important processes.

Sufficient number of Interrupts: whenever a device or a
process requires attention, the real-time operating system must
be capable of noticing the need of the device or process.
Some real-time operating systems are considered to be embedded,
this means that they are packaged as part of a micro-devices.
Mr.A.Gatt
Page 35 of 88
Form 5 Computer Studies Notes
3.5.2 Batch OS
Batch operating systems where very common in the early days of
operating systems; however one must not think that these are not
used anymore.
In a batch operating system, a number of tasks are assigned to the
computer, and these tasks are executed one after the other. So before
a task is executed its previous task must be first carried out. If there
are six different tasks which need to be
done, the sixth task is only done after the
first five have been carried out one after the
other. An important aspect is that these
tasks
are
carried
out
without
human
intervention. So, once the tasks have been
assigned to the computer, no interaction
with the machine is needed for the tasks to be executed.
To this day, elements of a batch operating system
are still used. When printing on a computer system
batch processing is used especially when more
than a file is printed. If for example seven
requests to print are passed on to the printer,
these requests are not processed simultaneously,
but they are batch processed. This means, that
these seven requests are placed after each other, and only when a
task is finished (in this case the prinout is ready), the consecutive task
is carried out.
Mr.A.Gatt
Page 36 of 88
Form 5 Computer Studies Notes
Another common example of batch processing is BAT files on Microsoft
Windows. By creating a file with a list of commands after each other,
the file can be submitted to the DOS shell, and each step is executed
after the previous step has been worked out.
The following code extract illustrates the contents of a batch file
(CFB.BAT) and it copies all the contents of Drive A to the current
directory.
@ECHO OFF
ECHO.
IF "%1" == "" XCOPY B:\*.*
IF NOT "%1" == "" XCOPY B:\%1
ECHO.
C:\BATCH\DR
3.5.3 Time sharing OS
In time-sharing operating system, multiple applications will seem to be
using the CPU at the same time. This happens because the CPU is able
to allot a time bracket (called time-slice) to each application. A timeslice is a small period of time when the CPU is available to execute any
tasks required from it.
If a CPU is given only one application to execute, the application would
be executed immediately leaving the CPU with idle time (time when it
is doing nothing). This idle time can be used to run other applications
at the same time; hence more than one application can run at the
same time.
Mr.A.Gatt
Page 37 of 88
Form 5 Computer Studies Notes
This concept is applied both to multi-user (when more than one user
uses the same computer) or single-user (when only one user uses the
computer).

Multi-user: In this case, since more than one user will be using
the same CPU, the CPU will allot a time-slice to each user.
Hence, it will go around all the users, one after each other
servicing their computing needs before going on to the next
user. Usually the time-slice is very small and it is measured in
milliseconds. If there are many users, each having a fair amount
of work being carried out, the CPU response time might be
degraded due to the high load of work.

Single-user: When a CPU is being used by a single user, the
idle time of the CPU is used to run multiple applications at the
same time. So, each application is assigned a time-slice, and the
CPU will go round the applications executing their requirements
in their alloted time-slice. Also, in this case if there are many
applications running, each with its requirements, the response
time for each application will degrade, resulting in overall
sluggishness.
3.5.4 The necessity of different OS's to support different modes and
configurations.
Depending on various scenarios, a different operating system can be
more suited than others. No operating system can be used to cater for
all scenarios. The following will illustrate different cases where a type
of operating system might be more suitable to use than others.
Mr.A.Gatt
Page 38 of 88
Form 5 Computer Studies Notes
Real-Time Operating System
As already mentioned before, real-time systems are very critical
because their response must be immediate. Due to this very short
response time, batch processing and time-sharing are definetely out of
question because these can have a somewhat long response time.
In the case of very delicate situations such as jetfighting, space shuttles or time-dependent situations
such as a production line, a real-time operating system
is the prime choice.
Batch Operating System
Although a batch operating system might be considered to be the
oldest type of operating system, its nature can be used for very large
quantities of data that needs to be processed.
In the case of a financial bank, where millions of cheques
are processed each day, it would be a cumbersome process
to input the details of each cheque, so what is usually done
is that all the cheques are collected and handed to the
operating system at the end of the day.
Since, a batch operating system does not require human intervention,
all
the
cheques
are
processed
automatically
and
by
morning
(hopefully!) all cheque processing will be done.
Mr.A.Gatt
Page 39 of 88
Form 5 Computer Studies Notes
Time Sharing Operating System
The main aim of a time-sharing operating
system is to utilise the idle time of a CPU. So,
in the case of having a large mainframe
system with a very powerful CPU, many other
terminals can be connected to it, so that
multiple users can use it, hence utilising the
idle time of the CPU.
3.5.5 Common types of operating systems – single-user, multiuser,
networked, single programming, multi programming.
Single-User: This allows one user at a time to use the computer. This
means that the computer will be exclusively used by one user at a
given point in time; therefore no other user can use the computer at
that time. Once the first user is finished with the computer, another
user can then use it.
Multi-User: This setup allows more than one user to use a computer
at a time. Usually, a mainframe (or minicomputer) is used for this
setup, and various input (and output) devices are connected to the
mainframe so that more than one user can use the system. Each user
would then have his/her own terminal along with his/her directories.
Usually, a password is required to access one‟s account.
Mr.A.Gatt
Page 40 of 88
Form 5 Computer Studies Notes
Networked: This type of operating system is specifically designed to
keep a network to run at its optimal performance. In a network there
are a number (more than 2) computers connected to each other, and
the main aims of a network operating system is to:

Control a network and its traffic,

Control access of users to different resources such as hardware
and/or files,

Provide administration features such as security.
Single-Programming: In this kind of operating system, a task must
be fully executed before a new task could be run. This operating
system is capable of running one task at a time, so no multitasking is
available.
Multi-Programming: In multi-programming operating systems, the
OS is capable of running more than one task at a time. This can be
carried out by using time-slicing, where each application is allocated a
small amount of time, where the CPU tends for the application. Since a
time-slice is usually very small (it can be around 1/60 second), the
user has the illusion that multiple applications are being run at the
same time.
Mr.A.Gatt
Page 41 of 88
Form 5 Computer Studies Notes
2.8 Dedicated Computer Systems
2.8.1
Difference
between
a
general-purpose
and
a
dedicated
computer.
A general-purpose computer is created with the main aim of
performing a variety of tasks. When using a PC one can perform a
multitude of tasks such as spreadsheets, word-processing, browsing
the Internet, playing games, creating music, editing videos, etc… So, a
general-purpose computer is not limited to a single task.
On the other hand, a dedicated computer is clearly
designed to do a single task. It does not have to be
a simple task, it can be somewhat complex, but a
dedicated computer can only do what it was
manufactured for. Common examples are Sony
Playstation,
ATM
(Automatic
Teller
Machines),
Mobile Phones, GPS (Global Positioning System).
2.8.2 Embedded and process control systems.
An
embedded
system
is
a
special-purpose
system
totally
encapsulated in the device it controls. Since it is not a general-purpose
system, its functions (the functions that this system does) are known
beforehand, and so engineers can reduce its size, and simplify it as
much as possible in order to be more easily embedded and cheaper to
produce. Typical examples of an embedded system are VCR (Video
Cassette Recorders), Washing Machines, Microwave Ovens, Alarm
Systems…
Mr.A.Gatt
Page 42 of 88
Form 5 Computer Studies Notes
For more information visit:
http://en.wikipedia.org/wiki/Embedded_computer
A process control system is the automatic monitoring and control of
an industrial activity by a computer that is programmed to respond to
the feedback signals from sensors. The operation controlled may be as
small as a single machine packing boxes or as extensive as the control
of an automated bakery, where the mixing, cooking and packaging are
controlled within a single integrated manufacturing process.7
2.8.3 Computerised appliances as an example of dedicated systems –
VCR, auto pilot, mobile phones, GPS, etc.
As previously mentioned, a special purpose (embedded) system is
capable of perfoming only a limited number of tasks. This can be
clearly seen in computerised appliances such as:

VCR: (Video Cassette Recorder) has a number of options which
are related to its task. For instance on a VCR one can find the
option to play, rewind, fast-forward a cassette. In modern VCR
one can also program the VCR to record what‟s on TV at a
specified time, and also one can program it to stop recording at
a
specified
time.
Other
computerised
features
might
be
automatic tracking, where the picture is made sharper and nicer
through constant monitoring of the tape by the VCR and
adjusting accordingly.

Auto-Pilot: Modern aircrafts especially passenger jets are
equipped with auto-pilots. This special-purpose machine helps
7
Source: A Glossary of Computer Terms 10th Edition Pg59
Mr.A.Gatt
Page 43 of 88
Form 5 Computer Studies Notes
the pilot to travel from one place to another with little
intervention. The auto-pilot automatically (or controlled by the
pilot) plots the route the aircraft needs to take and then the
speed and altitude and many other variables are controlled by
this dedicated machine.

Mobile Phones: The technology advancements in computing
made it possible to integrate very small dedicated machines into
mobile phones. These machines apart from handling normal
mobile phone functions such as making or receiving a call, can
also
handle
more
features
such
as
sound
management,
messageing management, WAP connectivity, JAVA programs and
more!

GPS: (Global Positioning System) make travelling easier and
safer too. This dedicated machines, help the user to keep track
of their location hence making it more difficult to get lost
especially when used on ships which have to cross large
stretches of oceans.
2.8.4 Specialised I/O devices (sensors, buttons, LCD).
One must also keep in mind that there are various forms of Input and
Output devices, not just the general ones such as keyboards, mice,
monitors, printers, etc… Some input/output devices are in the form
that suits the machine they were created for.
Mr.A.Gatt
Page 44 of 88
Form 5 Computer Studies Notes
Sensors
A sensor is an electronic component which converts one
form of energy into another; for example: a thermistor
converts a temperature into electrical energy with varying
voltages. The sensor responds to some physical property
such as pressure, rate of flow, humidity amongst others.
Some examples:

Alarm Systems: When an alarm system is installed, every door
or window will have a sensor. This sensor detects whether the
door or window is open. If the door or window is closed, the
sensor will not do anything, but if the sensor detects that the
window has been opened the alarm system will go off.

Climate Control: Air-conditions have sensors to detect the
temperature in a room. So, when a temperature is set, the airconditioner will constantly monitor the temperature of the area
through the sensor and react accordingly.
Buttons
Another common form of input is the button.
Buttons are included in almost all computerised
appliances and these act as the main source of
input from the user to the machine.
Mr.A.Gatt
Page 45 of 88
Form 5 Computer Studies Notes
LCD
Liquid Crystal Display allows the
computer
to
deliver
back
the
output. This is especially used for
example in GPS systems, where
the current location on the map is
displayed on the LCD screen. With
the advances in this technology
and reduction in prices, the LCD screen is more likely to be included in
more special-purpose machines.
LED
Light emitting diodes have been used for quite a
long time, and are still very common. LEDs are
very small diodes that can generate a small
amount of light (requiring very little electricity)
usually in the colour of green, red or blue. This type of output indicates
various states of the dedicated-machine. Almost all appliances when
turned on have a small LED which indicated that the machine has been
turned on.
Mr.A.Gatt
Page 46 of 88
Form 5 Computer Studies Notes
2.8.5 Software for dedicated computer systems
Dedicated computer systems have specially made software which is
solely aimed to perform the required tasks and thus cannot handle
out-of-the-routine functions.
This software usually resides in the ROM of the dedicated computer
because it never needs to be changed. (Although in certain cases
where the software needs to be changed, the ROM is flashed and the
new software is put into it.) Dedicated computer systems usually have
a limited amount of RAM as well which will aid the computer system to
store temporary results.
Mr.A.Gatt
Page 47 of 88
Form 5 Computer Studies Notes
3.4 Networks
3.4.1 Networking LAN and WAN
A network is a linked set of computer systems capable of sharing
computer power and resources such as printers, large disk-drives, CDROM and other databases
There are two main types of networks being:

LAN (Local Area Network): This is a network in which the
computer systems are all situated relatively close to each other,
for example in the same building or cluster of buildings, such as
a school. Since the distances involved are small, direct physical
connection is possible. The network connections are normally
wire cables, such as coaxial cable, but fibre optic cable is being
increasingly used.

WAN (Wide Area Network): This is a network in which the
computers are geographically remote. Wide area networks make
use of a range of connection methods including communication
satellites.
8
8
Source: A Glossary of Computing Terms 10th Edition Pg67
Mr.A.Gatt
Page 48 of 88
Form 5 Computer Studies Notes
3.4.2 Advantages of a LAN
Clearly
the
communication
between
various
computers
has
its
benefits, these mainly being:

Easier
Communication:
The
networked
computers
can
communicate with each other. This can be done through text
(instant messaging) or video (using a web-cam).

Device Sharing: Peripheral devices can be shared with the
networked computers. So, a single printer can be purchased,
and all computer connected to the network can print to that
printer. This clearly saves a lot of expenses, since less hardware
needs to be purchased. Since modems can also be shared,
Internet connection can be shared as well. A single Internet
connection can be subscribed to (usually Business connection)
and the all the networked computers would have access to
Internet.

File Sharing: File server allows the sharing of data resources.
So, users from different machines can update the same data
source, this will keep the data updated throughout the whole
network ensuring consistency of data.

Easier Administration: Network administrator can manage
hardware resources and update any software from the main
server.

Expandable: Network is easily expandable since only a network
card and a network point are required to connect a new terminal
to the networked system.
Mr.A.Gatt
Page 49 of 88
Form 5 Computer Studies Notes
However, there are also some drawbacks of having a network:

Start-up Cost: The cost to start and implement (initial-cost) of
a network is quite expensive.

Break-downs: If the file server breaks down, the other
computers will not be able to access the files stored on the file
server.

Viruses: Viruses can spread very quickly, since the computers
are all connected together.

Security: Data security becomes very important, because since
many users use the network, there has to be the proper data
security to control hacking and unauthorised access.
3.4.3 Use of modems
The
term
modem
derives
from two words Modulate and
Demodulate which basically
refer to what the task of a
modem
is.
The
modem
allows the computer to be
connected to a telephone line
so
that
data
can
be
transmitted and received.
Mr.A.Gatt
Page 50 of 88
Form 5 Computer Studies Notes
There are various different modems available:

External PSTN9 Modem: This modem is simply plugged into
the computer via the serial port, and it has its own power
supply. The telephone cable is plugged into the modem.

Internal PSTN Modem: This is the same as the external PSTN
modem, but it is directly connected to the motherboard (hence it
is found inside the tower) and it does not need external power.

ADSL10 Modem: The ADSL modem is generally external, and it
plugs to the PC using either USB or using the network interface.
It still uses the PSTN line but a special filter is used so that data
can be passed both ways and making the service much faster
than normal dial-up.

Cable Modem: The cable modem does not use a telephone line,
but instead it uses cable (the same cable used for TV) to connect
to the ISP.
The main task of the modem is to convert sound signals into electronic
signals.
The
telephone-lines
used
by
modems,
use
analogue
technology which is not compatible with computers. The modem is
therefore used to convert those analogue signals into digital signals.
When information is being sent, the digital data sent by the computer
is delivered to the modem, which converts it to analogue data which in
turn is transferred to the telephone line. When information is being
received by the PC, information from the telephone line is converted
from analogue to digital by the modem, which in turn delivers it to the
computer.
9
PSTN: Public Switched Telephone Network – the network used for normal telephony
ADSL: Asymmetric Digital Subscriber Line – based on PSTN but uses different technologies which
allow two-way communication
10
Mr.A.Gatt
Page 51 of 88
Form 5 Computer Studies Notes
Digital data is passed
to the modem.
Modem receives
analogue data.
1010101
1110101
0000….
1010101
1110101
0000….
The modem converts it into
analogue, since the telephone
line is analogue.
Data is converted
back into digital
format.
Figure 14: Modulation / Demodulation
The baud rate of modem determines how fast information is sent or
received by the modem. Most dial-up modems have a speed of
56Kilobits (56kbps/sec), but most modern modems such as ADSL can
reach speeds of 4096Kbps/sec.
For more information visit:
http://en.wikipedia.org/wiki/Modem
3.4.4 Use of WANS for email, WWW, Video Conferencing
WANS allow computers which are located in different geographic
locations to communicate with each other. This communication allows
for a number of services which enhance this type of communication.
Mr.A.Gatt
Page 52 of 88
Form 5 Computer Studies Notes
E-Mail (Electronic Mail)
E-Mail is one of Internet‟s services. The main aim of the Internet is to
allow computers send „instant‟ messages from one computer to
another. According to Darwin Magazine, the first e-mail was sent in
1971, prior to this date, messages could only be sent to users on a
single machine. Ray Tomlinson‟s breakthrough was the ability to send
e-mails to anyone connected to the Internet by using the now common
e-mail address with the „@‟ symbol.
An e-mail message is basically a short text file, although from its early
days it has evolved, and so users can attach files, and even include
HTML in their messages.
Each e-mail address is made up of the username (which is chosen by
the user) and the domain the part after the „@‟ symbol which carries
the name of the host of the e-mail service, for example:
james@hotmail.com
There are two main types of e-Mail:

e-Mail services which are accessed by a standalone applications
such as Outlook, Thunderbird and

Free e-Mail services which are accessed through a web-site.
Such free services are Yahoo!, Google, and Hotmail.
Mr.A.Gatt
Page 53 of 88
Form 5 Computer Studies Notes
An e-mail server is required to send e-mails from one computer to
another. This e-mail server needs to have two services:

SMTP (simple mail transfer protocol) which is used to send
e-mails.

POP3 (post office protocol 3) is used to receive e-mails.
If for example anne@yahoo.com sends an e-mail to john@hotmail.com
the e-mail message will follow this path.
Yahoo! Mail
Server
Hotmail Mail
Server
SMT
P
SMT
P
POP
3
john@hotmail.com
anne@yahoo.com
Figure 15: E-Mails
The main advantages of e-mails are:

Speed: Very fast, the moment an e-mail is sent in just a few
seconds it will be delivered to the recipient.

Asynchronous: E-Mail messaging is asynchronous which means
that communication does not occur at the same time. Therefore
after the sender sends the e-mail, the recipient can reply at
his/her convenience unlike real-time chatting.
Mr.A.Gatt
Page 54 of 88
Form 5 Computer Studies Notes

Cheap: E-Mail is inexpensive, many companies such as Yahoo!,
GMail, Hotmail offer free e-mail services. Also, each e-mail send
is free unlike conventional post (or snail-mail) where an
envelope and a stamp have to be purchased. Also, the same
message can be sent to a large group of recipients.

Environmental
Friendly:
E-Mail
is
environment-friendly,
because no paper is used.
Disadvantages of e-mail are:

Not Everyone Has It: Not everyone has an e-mail address
whereas by using normal post, everyone can be reached.

Privacy: A threat to privacy and security. If the password is
known there will be total access to the e-mail service.

SPAM: SPAM mail is very common and very difficult to get rid
of. Many messages advertising products or scams are sent to email addresses without the user‟s permission.

Only Virtual Messages: No tangible products can be sent.
For more information on how e-mail works visit:
http://computer.howstuffworks.com/email.htm
WWW (World Wide Web)
WWW is a collection of information held in multimedia form on the
Internet. This information is stored at locations called Web Sites in the
form of Web Pages. A web page is a single document. It may be too
large to be displayed as a screen without scrolling.
Mr.A.Gatt
Page 55 of 88
Form 5 Computer Studies Notes
Web pages are permanently available to any user of the Internet. Each
organisation (and many individuals) providing information, organise
their information as a web-site, often consisting of many pages. Web
sites are an effective way of distributing information such as
advertisements, technical information, comments and ideas.
Any web page can be accessed directly if its full address is knows, but
to make locating information easier each web site has a home page
(welcome page) which provides a starting point for a user to search
the site. Any web site can provide links to other related web sites.
Since browsers and search engines can quickly find pages of interest,
users are provided with the tools to surf the Internet. Surfing means
to search for useful information, following whatever routes may seem
interesting.
Web pages are usually prepared using HTML (hyper-text mark-up
language)11, although nowadays PHP or ASP are used in order to
connect a website to a database and CSS is used for a much neater
design.
For more information visit:
http://en.wikipedia.org/wiki/Www
11
Source: A Glossary of Computing Terms 10th Edition Pg42
Mr.A.Gatt
Page 56 of 88
Form 5 Computer Studies Notes
Video Conferencing
Video conferencing is used to allow two or more people situated in
different geographic locations to transmit both video data and audio
data simultaneously in order to be able to communicate with each
other.
A videoconference allows participants
to communicate and collaborate as if
they were in the same room. In order
to participate in video-conferencing,
the
necessary
software
is
required
(such as MSN Messenger, Skype or
iVisit), along with a microphone to
deliver
sound,
speakers
to
receive
sound and a digital video camera connected to the computer to
transmit the video feed.
A video conference can also be conducted on the Internet using a web
browser and a web server, and in which case it is called a web
conference.
3.4.5 Server and client machines; the problem of bandwidth at a
general level.
Client-server relationship is a method of network organization in which
stations make use of resources available at one or more servers. This
is the kind of organization seen in a star network (explained below); in
which one computer has the role of central resource manager for the
Mr.A.Gatt
Page 57 of 88
Form 5 Computer Studies Notes
network. Other forms of network can also operate with a client-server
relationship.12
The server is a computer offering a service (files, printers, database,
CD-ROM) and handles the requests by a client which asks to make use
of these resources. Some types of servers are:

File Server: provides central disk storage for any users of the
network. The file server software identifies each user‟s files
separately so that other users cannot use them. Users can
access their own files from any client station on the network.

Printer Server: allows all the clients stations to use a printer
controlled by it and usually provided and usually provides the
facilities of a print spooler.

CD-ROM Server: allows all the clients stations to obtain data
from a CD-ROM disk currently being used by the CD-ROM server
computer. Often a CD-ROM server will have access to many CDROM disks, either from a collection of several CD-ROM players,
or from a CD-ROM jukebox.

Database Server: manages a large database. Client stations
can access data in the database and, if authorized, can maintain
the database. The database processing is usually carried out by
the server, with the query being sent by a client station of the
server and the results assembled by the server and returned to
the client station.13
One of the main problems with client-server technologies is bandwidth.
Bandwidth determines the amount of data that can travel through the
network at any given moment. So, if for example in a LAN setup the
12
13
Source: A Glossary of Computing Terms 10th Edition Pg72
Source: A Glossary of Computing Terms 10th Edition Pg73
Mr.A.Gatt
Page 58 of 88
Form 5 Computer Studies Notes
bandwidth‟s capacity is 100Mbits/sec, that means that at any second
the maximum amount of data that can pass through the network is
100Mbits. This may lead to some problems if the data that needs to be
passed through the number is greater than this limit. In that case the
communication between the computers will be degraded.
Network Topology
This refers to the layout of the network; i.e. how the computers are
connected to the network. This usually depends on the need of the
network and is heavily determined by the building that will host the
network. The following will illustrate the main types of setups.
Bus Network
A bus network, allows the computers to be connected to the network
line, one after each other, as can be seen from the diagrams.
COMPUTER
COMPUTER
COMPUTER
COMPUTER
Each computer has the network cable going into its network interface and
another cable going out from the network interface to another computer.
COMPUTER
COMPUTER
COMPUTER
COMPUTER
COMPUTER
Each computer is connected to the bus network cable via a spur.
Mr.A.Gatt
Page 59 of 88
Form 5 Computer Studies Notes
Ring Network
A ring network has each of its computers connected to a network ring
along which signals are sent.
COMPUTER
COMPUTER
COMPUTER
COMPUTER
COMPUTER
COMPUTER
Each computer has the network cable going into its network interface and
another cable going out from the network interface to another computer.
COMPUTER
COMPUTER
COMPUTER
COMPUTER
COMPUTER
COMPUTER
Each computer is connected to the ring network cable via a spur.
In both bus and ring network setups, it is usually preferable to connect
the computers to the network using spurs. This is preferred because if
a computer malfunctions, the rest of the network will not be affected.
In the case of the network setups without the spurs, precautions must
Mr.A.Gatt
Page 60 of 88
Form 5 Computer Studies Notes
be taken to prevent a malfunction of the whole network, if a computer
malfunctions.
Star Network
In a star network all devices are connected to one central computer
(such as a file server). The central node (called hub) is a computer
which has separate connections to each computer.
COMPUTER
COMPUTER
COMPUTER
SERVER
COMPUTER
(HUB)
COMPUTER
COMPUTER
COMPUTER
COMPUTER
Each computer is connected to the central computer.
Mr.A.Gatt
Page 61 of 88
Form 5 Computer Studies Notes
5.3 Data Security and Privacy
5.3.1 Need of data security and integrity of data.
Data is one of the most important and essential asset of businesses.
Data must be safeguarded all the time, and every effort is required to
keep data reliable and updated.
Data integrity describes the correctness of data both during and after
processing. Data may be changed by the processing but will still have
integrity. Safeguards are needed to make sure that the data has
integrity by detecting any accidental or malicious change to the data.
Data security involves the user of various methods to make sure that
data is correct, is kept confidential and is safe. Data security includes
ensuring the integrity and the privacy of data, as well as preventing
the loss or destruction of data.14
5.3.2 Backups (the generations of files: grandfather, father, son files),
A master file is used to store the data found on the database. Usually
it stores data which is mostly static and does not change frequently.
However, data can be changed or added as necessary through
updating during processing.
The transaction file is used to keep track of all the changes made to
the database throughout the day. These changes are not immediately
entered into the master file; instead they are stored in the transaction
14
Source: A Glossary of Computing Terms 10th Edition Pg111
Mr.A.Gatt
Page 62 of 88
Form 5 Computer Studies Notes
file. At the end of the day, all the contents stored in the transaction file
are transferred (merged) to the master file to obtain a new and
updated master file.
The following is a simple example of a master/transaction file process.
Master File
Transaction File
Grandfather
Transaction File
Father
Update
Master File
Update
Son
Master File
Figure 16: GFS Backup System
As you can see from the above diagram, in the Grandfather section we
started with a master file and a transaction file which when combined
together created a new Master File (Father). This in turn was combined
with another Transaction File to obtain the last Master File (Son).
This Grandfather, Father, Son hierarchy is used for safety. Suppose
the last Master File (Son) got corrupted by accidental deletion or
corruption of data, the same Master File can be re-created by
Mr.A.Gatt
Page 63 of 88
Form 5 Computer Studies Notes
combining the father Master File with the respective Transaction File to
obtain the son file once again.
5.3.3 Physical security and software safeguards.
Physical Security
The most obvious choice of protecting data is to place it in a safe
secure place. Data can be stored in a limited-access room; such a
room would prevent unauthorised access. This room can be protected
either by a normal lock-and-key approach, or by more sophisticated
methods such as ID card scanning and biometrics (using human
features
for
security
such
as
retina-scan,
fingerprint-scanning).
Another physical approach would be to store data in a safe where only
very few persons know the combination to it.
Another
basic
security
system
physical
is
the
write-protect option found
on certain devices. Some
devices, such as the floppy
or
tape
have
mechanisms
that
read-only
prevent
the user from accidentally overwriting data. These can be simply
activated by positioning the read-only lock in the desired position.
Mr.A.Gatt
Page 64 of 88
Form 5 Computer Studies Notes
Software Security
There are many software measures which can protect data. The
following highlights some of the most common approaches.
IDS (Intrusion Detection System)
IDS monitors the operation of the network to detect and warn when
illegal operations are being carried out. The system may be serverbased, detecting attacks on the operation of the file-server, or they
may be a network based, watching the pattern of traffic across the
network.
User ID (User Identification)
A user ID is a unique name or code used to identify a user to a
computer system when gaining access (logging in). The systems
manager or systems management software allocates user IDs to new
users.
Checks must be made to verify that the person logging on is the
correct „owner‟ of the user ID. Methods of checking include:

Passwords: are words or codes known only to the user. A
password is linked to a specific user ID. Although a user ID may
be generally known to others, access can only be gained with the
correct combination of user ID and password.

Personal Identification Devices: is usually a plastic card
which identifies the user and acts as an electronic key. Most
cards have a magnetic stripe which stores information. This
Mr.A.Gatt
Page 65 of 88
Form 5 Computer Studies Notes
information can be read by a computer and used as a user ID.
Unauthorised access is made difficult because an unauthorised
user must have the personal identification device. Additional
protection can be provided by the use of a personal identification
number. Key-card is another name for this device.

Personal Identification Numbers (PIN): is a number used as
a password, particularly with bank cards and credit cards.
Biometric
This is a unique physical characteristic of an
individual which can be checked automatically by
a computer. The individual‟s biometric is measured
by a special scanner and used with the user ID in
a similar way to a password. Finding physical
characteristics which cannot be copied has been
difficult but viable systems include fingerprints and
retina scans (the pattern of veins at the back of
the eye). Face recognition and voice samples have proved to be
unreliable for use as a biometric.
Encryption
Encryption makes data in a computer system unintelligible. The
encrypted data appears to be meaningless and is sometimes described
as scrambled data. Encryption provides security for the data (by
preventing it being understood), both when stored electronically and
when
transmitted
between
computer
systems.
Decryption
converting the unreadable data back into understandable form.
Mr.A.Gatt
Page 66 of 88
is
Form 5 Computer Studies Notes
An encryption key is a word or code selected by the user to govern the
encryption process. A decryption key is needed before the data can be
understood.
In conventional systems both encryption and decryption keys are the
same and therefore all users must have a copy of the key. If the
number of users is mall and the concern is for the security of stored
data, a single encryption key is usually sufficient. If transmission,
rather
than
storage,
requires
extra
protections
then
different
encryption and decryption keys may be used.
Digital Signature
This is the special encryption of data, used to indicate that the data is
genuine. If the recipient of the data can correctly decipher the digital
signature then the data should be correct (and forged data is unlikely
to have been substituted).
Digital Certificate
This is an encrypted message provided by a certification authority
which confirms that the individual is who they claim to be in an on-line
communication. It includes a digital signature, which can be confirmed
by sending a secure message to the certification authority.
The certification authority, also known as a trusted service provider or
a trusted third party, is a business that provides online certification
facilities. These organisations are trusted to check the identity of the
Mr.A.Gatt
Page 67 of 88
Form 5 Computer Studies Notes
online users and provide them with encrypted messages (the
certificates) which can be confirmed by checking the certificate with
the certification authority.15
5.3.4 Software piracy and copyright.
Software Piracy is the unauthorized duplication,
distribution or use of computer software; for
example, making more copies of software than
the
license
licensed
for
allows,
one
or
installing
computer
onto
software
multiple
computers or a server.
Copying software is an act of copyright infringement, and is subject to
civil and criminal penalties. It's illegal whether you use pirated
software yourself, give it away, or sell it. And aiding piracy by
providing unauthorized access to software or to serial numbers used to
register software can also be illegal.
These are four of the most common types of software piracy:

Soft-lifting: This happens when a persons buys software with a
single license and installs it on more than one PC or installs it on
other people‟s machines. The exception is that one can make a
single copy of the software but only as a backup purpose.

Hard Disk Loading: Many computer vendors install software on
a new PC without selling the software itself. This is done, to sell
a fully loaded machine at very low prices because the user is not
charged for the software.
15
Source: A Glossary of Computing Terms 10th Edition Pg113-117
Mr.A.Gatt
Page 68 of 88
Form 5 Computer Studies Notes

Downloading:
(broadband
With
many
connectivity)
advances
downloading
in
communications
software
from
the
Internet is much quicker and easier. Many P2P (peer-to-peer)
applications
exist
(such
as
Torrents)
which
facilitate
the
download of illegal software.

Software Counterfeiting: Software is copied illegally and resold. Some counterfeited software can be very obvious because
only
the
CD
„sophisticated‟
(or
storage
counterfeited
media)
is
software;
sold,
but
everything
in
more
will
be
reproduced including the box, the manuals, etc…
Copyright
Copyright
is
a
protection
that
covers published and unpublished
literary,
works,
scientific
whatever
and
the
artistic
form
of
expression, provided such works
are fixed in a tangible or material
form. This means that if you can
see it, hear it and/or touch it - it
may be protected. If it is an essay, if it is a play, if it is a song, if it is a
funky original dance move, if it is a photograph, HTML coding or a
computer graphic that can be set on paper, recorded on tape or saved
to a hard drive, it may be protected.
Mr.A.Gatt
Page 69 of 88
Form 5 Computer Studies Notes
Copyright laws grant the creator the exclusive right to reproduce,
prepare derivative works, distribute, perform and display the work
publicly. Exclusive means only the creator of such work, not anybody
who has access to it and decides to grab it.16
When software is purchased there will be a software licence (also
known as the licence agreement) which sets conditions for the use of
the software. These conditions vary considerably between products.
Any use of the software not allowed by its licence is illegal. In practice,
this means that copying software bought by someone else is likely to
be an offence. Special licenses are needed for some cases, for example
multiple use on a network.17
5.3.5 Ethical and legal issues.
Ethical Issues
Software development involves a team effort that blends the creative
ideas and talents of programmers, writers and graphic artists. And like
most creative works, such as books, music and films, computer
software is protected by U.S. copyright laws.
When you purchase software, you do not become the owner of the
copyright. Rather, you are purchasing the right to use the software
under certain restrictions imposed by the copyright owner, typically
the software publisher. The precise rules are described in the
documentation accompanying the software -- the license. Most often,
they state that you have the right to load the software onto a single
16
17
Source: http://www.whatiscopyright.org/
Source: A Glossary of Computing Terms 10th Edition Pg120
Mr.A.Gatt
Page 70 of 88
Form 5 Computer Studies Notes
computer and make one backup copy. If you copy, distribute or install
the software in ways that the license prohibits, whether you are
swapping disks with friends and co-workers or participating in
widespread duplication, you are violating federal copyright law.
Using copied or counterfeit software also means:

Greater exposure to software viruses, corrupt disks, or otherwise
defective software

Inadequate or no documentation

No warranties

Lack of technical product support available to properly licensed
users

Ineligibility for software upgrades offered to properly licensed
users.
Software piracy is not a victimless crime. Piracy denies the software
developer its rightful revenue and harms consumers and the industry
as a whole. All software developers, both big and small, spend years
creating software. A portion of every dollar spent in purchasing original
software is funnelled back into research and development, so that
newer, more advanced software can be produced. When you purchase
illegal or counterfeit copies, your money goes straight into the pockets
of software pirates.18
18
Source: www.bsa.org
Mr.A.Gatt
Page 71 of 88
Form 5 Computer Studies Notes
Legal Issues
Apart from a degraded software experience, and any ethical issues
that may arise from software piracy, there are also some serious legal
issues.
In the USA, software theft is a serious matter. If you or your company
would be caught copying software, you may be held liable under both
civil and criminal law.
If the copyright owner brings a civil action against you, the owner can
seek to stop you from using its software immediately and can also
request monetary damages. The copyright owner may then choose
between actual damages, which include the amount it has lost because
of your infringement as well as any profits attributable to the
infringement, and statutory damages, which can be as much as
$150,000 for each program copied.
In addition, the government can criminally prosecute you for copyright
infringement. If convicted, you can be fined up to $250,000, or
sentenced to jail for up to five years, or both.19
19
Source: www.bsa.org
Mr.A.Gatt
Page 72 of 88
Form 5 Computer Studies Notes
5.3.6 Hardware and software procedures which deter piracy - serial
numbers and activation keys, hardware keys (dongles).
Software developers try to protect their software by implementing
various methods to deter piracy. These are:

Serial Numbers: Certain software will ask the user to input a
serial number when installing the software. If the number is not
inputted or entered incorrectly, the software will not install,
making the pirated copy useless. If the serial number is entered
correctly, the software will install and be fully functional. In
some cases the serial number is checked with the company
using an Internet connection to make sure that it has not been
previously used by another user, making it more difficult to
duplicate serial numbers.

Activation Keys: After the software is installed, the user is
required to enter some text (the activation key) so that the
application will work. This activation key is usually obtained from
the vendor of the application – the user will send an e-mail with
the product ID of the application, and after the vendor will
confirm that the software is indeed original; it will send the
activation key which will unlock the software.

CD (or DVD) Copy Protection: Most companies will create a
special program when burning their application to the storage
medium which will prevent users from copying the software by
normal means.

Hardware Keys: In this case a hardware device (such as a USB
pen) is given with the software and for the software to be
functional the dongle must be connected to the machine.
Mr.A.Gatt
Page 73 of 88
Form 5 Computer Studies Notes
5.3.7 Software registration.
Most software can be registered with the company that supplies the
software. The user fills in some personal details such as name, address
and e-mail. This will allow the company to serve better its customers:

Updates: The software company can inform its registered
members with news about the product. This may include news
about new program releases, new updates or new patches to the
program. Sometimes, when a surface address is supplied,
updates and patches are sent by post on a CD.

Bonus Features: Certain companies create bonus features to
the program (also called extensions, add-ons or expansion
packs) which might be free to registered users.

Discounts: Registered members usually benefit from discounts
on applications released by the same company.

Technical Support: Some companies offer technical support
(such as forums or live chatting) about their program only to
registered members.
5.3.8 Access rights. Privacy on multi-user/network systems.
Access rights control whether or not a particular user can use or edit a
program or a data file. Each user is assigned rights which determine
the files that can be accessed. A user may be allowed complete access
to a file (including altering the data), may be restricted only to read
the data (or part of the data) or have no access at all. Technical
personnel may have more substantial rights. Access rights can also
restrict the use of a file to a particular workstation or user.
Mr.A.Gatt
Page 74 of 88
Form 5 Computer Studies Notes
With the simpler operating systems used on stand-alone computers
the actual user is normally not identified. The access rights can easily
be changed but provide a way of preventing some mistakes (for
example deleting important files).
The more complex network operating system provides a way of
identifying individuals (for example by a user ID and password). Each
individual can only access resources the user is given privileges for by
the network manager. The user may have ownership of some files and
can then set the access rights to restrict who else can use the files.
Some files have additional access restrictions provided by password
protection. When a user attempts to gain access to one of these files
an additional password will be requested before access is allowed. This
provides extra security since knowing a user‟s system password is not
enough to gain access to the data. The password is often used as the
encryption key to encrypt the data, making the data meaningless even
if unauthorized access to the system is achieved.20
20
Source: A Glossary of Computing Terms 10th Edition Pg116
Mr.A.Gatt
Page 75 of 88
Form 5 Computer Studies Notes
5.2 Effects of Computer-Based systems on Individuals, Organisations
and Society
5.2.1 Positive and negative effects of computerisation
In these last years, computer use amongst people has increased
greatly. This computerization can have both positive and negative
effects on the individual, an organization or the society. The following
will highlight some of the positive and negative aspects in several
different areas.
Computers and Work
Negative

Jobs are decreased, since computers are replacing humans in
such cases as ATM (automatic teller machine), telephone
operators, meter readers, film processors.
Positive

New jobs are created in the computing industry such as the
hardware industry, software industry and web-design industry.

Computers increase productivity and overall quality leading to
cheaper and better products.
Mr.A.Gatt
Page 76 of 88
Form 5 Computer Studies Notes
Computers and the Workplace
Negative

Possible less face-to-face communication.

Very fast technology advances might lead to job disruption in
order to adopt (or adapt) to new technologies.

Employees might feel that constant monitoring can affect their
privacy and dignity.

Constant use of computers can lead to RSI (repetitive strain
injury) if the proper precautions are not adopted.
Positive

Employee has more information available which allows the
employee more decision-making freedom.

Various tools available on the computer can enhance the work
experience and reduce the overall work-load.
Computers and Society (involving the Internet)
Negative

Reduced human contact, since people prefer chatting rather than
socialising.

Community groups‟ attendance decreases, once again due to
lack of involvement.

Erodes family life and community values.
Positive

Facilitated communication with relatives, friends and other close
persons.
Mr.A.Gatt
Page 77 of 88
Form 5 Computer Studies Notes

Routine tasks can be done quickly, hence leaving more free time
to spend with close relatives.
Computers and the Individual
Negative

Addiction to the Internet.

Addiction to games; especially in youngsters which deter a
healthy lifestyle since they do not participate in outdoor games

Less socializing.

Being lazier; since Internet can be used as a source for readymade material.
Positive

More work can be done in less time with the adequate tools on
the PC.

Facilitates access to services by using websites for buying
products or paying bills.

More
information
at
the
user‟s fingertips
with
interactive
encyclopaedias and the constantly updated Internet.
Mr.A.Gatt
Page 78 of 88
Form 5 Computer Studies Notes
5.4 Multimedia
5.4.1 Brief overview of capabilities and trends.
Multimedia is the presentation of information by a computer system
using graphics, animation, sound and text. The data may be stored in
a variety of ways using conventional computer storage devices,
together with a picture database on CD-ROM (or DVD-ROM). Output
might be through VDUs, sound-generators and laser projectors.
Integrating a tutor program could allow the system to be used as a
training resource. The performance of the user could then be
monitored by recording the choices made in response to questions and
evaluating this response using an expert system. This performance
output might then be sent to a remote trainer who would assess the
trainee‟s progress.
Interactive Video
This involves the user of a computer linked to a large capacity data
store such as DVD to provide random access retrieval of images
(including stills and continuous video) and sound. Data, once recorded,
is not easily changed or added to and access times can sometimes
appear
long.
However,
any
disadvantage
arising
is
generally
outweighed by the amount, variety and quality of data which can be
retrieved from one active device.
Mr.A.Gatt
Page 79 of 88
Form 5 Computer Studies Notes
Browse
This is a feature of hypertext systems which allow users to build their
own route through an application rather than following a predetermined one. The route so chosen may be remembered by the
system so that it can be re-traced back to the starting point of that
route. This kind of browsing is particularly useful in such applications
as computerised manuals; computer aided learning packages and
large databases.
Video Clip
A video clip is a short section of film or video stored in digital form
(both sound and pictures). It is easily incorporated in computer
displays. The video clip would normally be stored in compressed form;
otherwise the storage cost would be prohibitive.
Video Data Compression
This is the use of electronic methods to reduce the amount of data that
has to be included when video data, either for still or moving pictures,
is stored or transmitted. For moving pictures (video), the principles
involve identifying those parts of the picture which change from one
scan to the next, and sending data only about changes, which is
known as delta compression. This alone will save a significant amount
of transmission and storage capacity. The Joint Photographic Expert
Group (JPEG) had defined standards for still picture compression, and
this format for storage or transmission is called JPEG. These standards
Mr.A.Gatt
Page 80 of 88
Form 5 Computer Studies Notes
have been extended by the Motion Picture Expert Group (MPEG) to
cover moving images. These proposals are currently being used for
video compression on CD-ROM and DVD. Sound is also compressed
using MP3 encoding and decoding mechanisms.21
5.4.2
Future
perspectives
(home
office,
access
to
public
and
institutional databases, libraries, high-quality sound and pictorial data
representation).
With advances in technology (faster CPUs, cheaper storage, very fast
Internet connectivity), multimedia possibilities are endless.
Public databases can be made accessible on the Internet, allowing a
large number of users to access its contents. Nowadays, various
websites offer free books (which do not have a copyright) to be read
from home by accessing their database. Universities can also publish
their work and research on Internet, which makes communication and
research with other universities much easier; this is also further helped
by video-conferencing which can encourage distant team-work.
By using video and sound compression, virtual tours can be created.
By using a standard interface a user can go on a virtual tour of a
historic or public landmark. This can be done by taking pictures (or a
video) of the place, edit it, and finally compile it, so that the user can
choose where to go by simply clicking the mouse. This can also be
enhanced by offering further details on visible items. So, if for
example, an art gallery is made virtual, various paintings can be
21
Source: A Glossary of Computing Terms 10th Edition Pg85,86
Mr.A.Gatt
Page 81 of 88
Form 5 Computer Studies Notes
clicked and a high-resolution photo will be displayed along with
information about the painting and painter.
By using many elements of multimedia, virtual reality can also be
achieved. Virtual reality is a computer generated environment which
provides the user with the illusion of being present in that situation.
Virtual reality is produced by providing feedback to our various senses:
vision, hearing, movement, and sometimes smell. As the user moves
or acts, the image seen will change along with appropriate sound and
movement. It usually requires high-powered computers. There are two
main types of virtual reality:

Immersive VR: these systems provide feedback to as many
senses as possible by using specialised equipment. They attempt
to provide the user with a very realistic situation and are used
for training in critical and stressful situations. Examples include
the training of aircraft crew and training maintenance engineers
to work in nuclear reactors.

Non-immersive VR: The systems use limited feedback to
provide the user with the perception of a particular situation
without attempting to convince the user that it is real. This can
be done relatively cheaply using common equipment. The
environment is displayed on a standard monitor using 3D
graphics and can be controlled using a simple pointing device
such as a special scalpel that a sculptor may use to carve a
sculpture. Other examples include vehicle driver training and the
ergonomic evaluation of a shop layout.22
22
Source: A Glossary of Computing Terms 10th Edition Pg86
Mr.A.Gatt
Page 82 of 88
Form 5 Computer Studies Notes
5.4.3 Basic hardware and software requirements and costs.
The basic requirement for multimedia is a PC which has a:

Video Card which is able to process images (and or moving
images) fast enough, especially if 3D image generation is
required.

Monitor (CRT or LCD) in order to be able to display most of the
multimedia components, such as pictures or videos.

Sound Card which is required to process sounds and generate
the required sounds through the speakers.

Speakers which are able to playback sounds.

CD or DVD drives which is generally required to store large
amounts of multimedia data.

Colour printer used to print images or text on paper.

Scanner which is used to transfer paper images to the computer
in order to manipulate them.

Input devices that are used to interact such as mouse, hand
glove (in case of VR), and any other kind of special device.
The above items illustrate the basic requirements which must be used
for a multimedia experience. However, the better the quality and
intensity of multimedia such as immersive virtual reality, the better
the machine must be. For instance in VR, a video-card must be very
powerful in its 3D image processing since almost everything is shown
in 3D. In case of sound, if sound is to be delivered using Dolby
SurroundTM sound, a Dolby-capable sound card and speakers are
required. The type of multimedia dictates the hardware requirements,
and the better the hardware the steeper the costs will be.
Mr.A.Gatt
Page 83 of 88
Form 5 Computer Studies Notes
3.2 Roles related to an I.T. Environment23
The EDP (electronic data processing) department is in charge of
various aspects related to I.T.; these can range from project
management to the quality control, when the product is finally
finished. The EDP has various roles, and each role can be assigned to a
number of employees, depending on the complexity and size of the
project. The EDP department needs to work together as a team, each
role with specific duties.
3.2.1 Information Systems Manager
The I.S. manager has the overall responsibility of the I.T. department
and sees that everything goes well and to plan. The I.S. manager
needs to monitor and encourage communication between different
roles to ensure project consistency. Some of the roles are:

Engage or disengage employees

Ensure that the department is satisfying the customer‟s needs

Create new opportunities for the company which can result in
company profits; such as taking on new projects.
3.2.2 Systems Analyst/Designer
The system analyst plays a vital role in the system analysis lifecycle.
The main task of a system analyst is to determine the input and
output requirements of a new project, and conduct feasibility studies,
to determine whether a project should be done or not.
23
Adapted from: A Complete Computer Course by Ivan Buttigieg Pg344-348
Mr.A.Gatt
Page 84 of 88
Form 5 Computer Studies Notes
In the case that the feasibility studies show that the project is not
feasible, the system analyst must propose whether to abandon it, or to
modify some of its aspects to make it feasible. If the project is
feasible, the main roles of the system analyst are:

Write down project details, including documentation manuals,
etc…

Prepare
test
data
in
collaboration
with
the
database
administrator

Provide instructions manuals (user and technical)

Supervising and maintaining the new system.
3.2.3 Systems Administrator
The role of the systems administrator is to ensure that all the software
required by the EDP is available and fully functional. This role is very
powerful because the systems administrator has got the rights to view
and/or modify all the files in the organisation. The main roles are:

Setting up the design of the database used by the organisation

Continuously maintaining the design of the database to reflect
changes and suit needs

Have extensive knowledge of the business rules

Testing database data integrity

Maintaining access rights of employees

Making sure to perform regular backups

Catalogue and index save files for future needs.
Mr.A.Gatt
Page 85 of 88
Form 5 Computer Studies Notes
3.2.4 Programmer
Once the project has been given to go-ahead by the systems analyst,
the work is passed on to the programmers. But before handing the
programming task to the programmers, the system analyst splits the
project into various modules. The programmers will then start the
planning, writing and testing of these modules so that they meet the
systems designer‟s requirements.
Programmers can be classified under two groups:

Senior programmers. There roles are to:
o Develop detailed plans (such as flowcharts) to be followed
by programming staff
o Schedule and co-ordinate junior programmers‟ work
o Set up the technical and the user help.

Junior programmers. There roles are to:
o Write the program
o Test the program by using supplied test data
o Correct any mistakes
o Prepare inline documentation (comments).
3.2.5 I.T. Trainer
The main role of the I.T. trainer is to guide computer users in the use
of organisation‟s software products. The trainer:

Lectures new employees on how to use the current EDP system
(logging, downloading or uploading, accessing files)

Teaches non-I.T. oriented people how to operate the hardware
and software applications

Co-ordinates training courses.
Mr.A.Gatt
Page 86 of 88
Form 5 Computer Studies Notes
3.2.6 Operator
The computer operator needs to make sure that the department‟s
system is working effectively. The operator has to:

Ensure that input and output media are ready for use

Power up machines to be used

Record computer errors into logbook

Monitor system‟s directory for suspicious or unwanted files

Keep computers clean

Regulate computer‟s environment.
3.2.7 Data Clerk
Data clerks enter information into the computer system. These
employees also check if the input and output information makes sense.
Examples include verifying all the data is present in a file, as well as
validating the source of the documents and eventually correcting any
errors found.
3.2.8 Web Master
The web master creates and maintains a web page and all the web site
links for the organisation. Usually the website will contain the products
/ improvements of the company, company vision and mission, support
information.
Mr.A.Gatt
Page 87 of 88
Form 5 Computer Studies Notes
3.2.9 Lab technician
The role of the lab technician is to ensure that all computers (the
hardware) are in correct working order. This person needs to:

Replace or repair faulty equipment

Install new hardware

Maintain „older‟ hardware in working condition.
3.2.10 Maintenance engineer
The
maintenance
engineer
knows
the
hardware
of
the
EDP
department‟s computer system thoroughly, and is present when the
company purchases new hardware. This person is required to:

Initially set up the system

Solve hardware problems which the technician might now have
enough knowledge about

Upgrade the computer system to make sure that everything will
work after the upgrade.
The End
Good Luck!
Mr.A.Gatt
Page 88 of 88