Form 2 (ICTL) : NETWORKS

COMPUTER NETWORKS :
A computer network is a system of interconnected computers and peripheral devices. For example, it may connect computers, printers, scanners and cameras.
Using hardware and software, these interconnected computing devices can communicate with each other through defined rules of data communications. In a network, computers can exchange and share information and resources.
A computer network may operate on wired connections or wireless connections.
When two or more networks are linked or connected and are able to communicate with one another using suitable hardware and software, it is called an internetwork.

BENEFITS OF COMPUTER NETWORKS ;
1. Computer network can share devices
2. Can share data and information
3. Can share internet access

COMPUTER NETWORKS DEVICES :
1. Switch
2. Router
3. NIC (Network Interface Card)
4. Hub
5. UTP cable (wired)
6. Wireless

COMPUTER NETWORKS :
1. LAN
2. MAN
3. WAN

DIFFERENCE OF COMPUTER NETWORKS :
1. Cost : LAN - low
MAN - high
WAN - higher
2. Network Size : LAN - small
MAN - larger
WAN - largest
3. Speed : LAN - fastest
MAN - slower
WAN - slowest
4. Number of computers : LAN - smallest
MAN - large
WAN - largest

NETWORKS TOPOLOGY :
1. Star topology
A star topology consists of a central host which acts as the centre, and all nodes connect to the host. A star topology is also known as star network.
A star network must have a host which acts as the centre - can be a server, hub or router.
In a star network, every node will not connect to the neighbouring nodes.
Every node must connect to the host in order to communicate.
The host will control the flow of communication in the network.

Advantages of star topology :
a) It is easy to implement. You only add nodes to the host.If one of the nodes fails, the star network can still function as long as the host is working.
b) The failure of a node does not affect the entire LAN. If the host fails, the network will fail to function.
c) There are no disruptions to the network when connecting or removing devices.
d) The network can be extended by adding new devices to the host or nodes.
e) Troubleshooting is easy when the host fails. Simply repair or replace the host and the network will continue to function.

Disadvantages of star topology :
a) If the host fails, the entire LAN will be affected.
b) Network speed decreases when the number of nodes increases.
c) Troubleshooting is difficult when one of the nodes fails.
d) A host must be installed to control the network.

2. Ring topology
A ring topology consists of all computers and other devices that are connected in a loop. Ring topology is also known as a ring network.

Advantages of ring topology :
a) Troubleshooting is easy when one of the nodes fails.
b) Repair or remove the failing nodes and the network will continue to function.

Disadvantages of ring topology :
a) Implementation is difficult. Network administrator has to terminate the entire network to install a new node between existing nodes.
b) A failing node will affect the entire LAN. If one of the nodes fails, the network will fail to function.
c) Network speed decreases when the number of nodes increases.

3. Bus topology
ABus networks are very common in Local Area Networks (LAN). A bus network must have a common backbone (the central cable) to connect all devices. A bus topology is also known as a bus network.

Advantages of bus topology :
1. Easy implementation. New devices can be added to the backbone or to the existing nodes.
2. Failure of a node doesn't affect the entire LAN.
3. No disruptions to the network when connecting or removing devices.
4. Network can easily be extended, by adding new devices to the backbone or existing nodes.

Disadvantages of bus topology :
1. If the backbone fails, the entire bus network will be affected.
2. Network speed decreases when the number of nodes increases.
3. Troubleshooting is difficult when one of the nodes fails.

Form 2 (ICTL) : Data Type

DATA TYPE :
1. Boolean - True/False, Y/N, L/P, ...
2. String - Fatehah, Ali, Jalan Bunga Raya, Melaka, Johor, Yusof, ...
3. Double - 1.1, 345.76, 23.8, 5678.345, 4.67, ...
4. Integer - whole number - 34, 5, 678, 12, 987, ...

Exercise :
1. How many data type in programming ?
2. For each data type, give another 3 examples.

Form5 ik : Constants & Variables & Data Type

5 Basic elements in programming.

1. Constant.
2. Variable.
3. Data Type.
4. Operators.
5. Control Structures.

Constants
Constant is a data container that stores information. The value will never change (remains constant) at any time during the course of a program.

Declare is the official term used in programming to announce to the program
the condition of statement in programming.

Variables
Variable is a data container that stores information. The value inside may change at any time during the course of a program.

DATA EXAMPLES FOR DIFFERENT DATA TYPES

Data type determines the type of data a variable can store, for example a number or a character. Examples of data types are integer, double, string and boolean.

Integer
Integer data type contains any whole number value that does not have any fractional part.
This is how we declare an integer type constant in Visual Basic statement.
This is how we declare an integer type variable in Visual Basic statement.

Double
Any number value that may and could contain a fractional part.
This is how we declare a double type constant in Visual Basic statement.

String
Any value that contains a sequence of characters.
This is how we declare string type constant in Visual Basic statement.

Boolean
Boolean type consists either a True or False value. Programmers usually use it to store status.
This is how we declare a boolean type constant in Visual Basic statement.

Form 2 (ICTL) : PROGRAMMING (copy this note)

PROGRAM

A computer program is a series of organised instructions that directs a computer to perform tasks. Without programs, computers are useless.
A program is like a recipe. It contains a list of variables (called ingredients) and a list of statements (called directions) that tell the computer what to do with the variables.

PROGRAMMING

Programming is a creation of a set of commands or instructions which directs a computer in carrying out a task.

Later these commands or instructions will be compiled and/or interpreted and then transformed to executable instructions that a computer or electronic device can execute or run.

PROGRAMMING LANGUAGE

A programming language is a set of words, symbols and codes that enables humans to communicate with computers.

It is a language used for writing computer programs, that direct a computer to perform computation and to organise the flow of control between mechanical devices.

EXAMPLES PROGRAMMING LANGUAGE

Hundreds of programming languages exist today. Each language has its own standard or rules for writing the commands and/or instructions.

Examples of programming languages are:
BASIC (Beginner’s All Purpose Symbolic Instruction Code)
Pascal
C
Cobol
Smalltalk

Program Development Phases

The five main phases of program development are as follows:

1. PROBLEM ANALYSIS PHASE
During the problem analysis phase, the programmer will interview the client to find out what the client’s needs are.

For example, the client might be a school that wishes to set up a school registration program. So the school administrator might tell the programmer that they need to record students’ data such as name, date of birth, gender, class, parents’ names, address and contact numbers.

2. PROGRAM DESIGN PHASE
Based on that, the programmer will design a flow chart that represents the needs of the client, which in this case is the school registration program.

3. CODING PHASE
Once the flow chart is confirmed, the programmer will perform coding.

4. TESTING AND DEBUGGING PHASE
The school registration program will be tested by the users at the client’s site. In this case, it will be the school office administrators. If there are any errors, the programmer will do a debugging of the program.

5. DOCUMENTATION PHASE
After this, the programmer will complete the documentation for the program; this includes the user manual, a clear layout of the input and output records and a program listing.