Computer Science AS CIE
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data-representation as5 主题
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multimedia as3 主题
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compression as2 主题
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networks-and-the-internet as11 主题
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computers-and-components as5 主题
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logic-gates-and-logic-circuits as2 主题
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central-processing-unit-cpu-architecture as6 主题
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assembly-language- as4 主题
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bit-manipulation as1 主题
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operating-systems as3 主题
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language-translators as2 主题
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data-security as3 主题
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data-integrity as1 主题
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ethics-and-ownership as3 主题
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database-concepts as3 主题
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database-management-systems-dbms- as1 主题
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data-definition-language-ddl-and-data-manipulation-language-dml as1 主题
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computational-thinking-skills as1 主题
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algorithms as4 主题
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data-types-and-records as2 主题
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arrays as2 主题
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files as1 主题
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introduction-to-abstract-data-types-adt as1 主题
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programming-basics as1 主题
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constructs as2 主题
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structured-programming as1 主题
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program-development-life-cycle as1 主题
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program-design- as2 主题
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program-testing-and-maintenance as3 主题
transmission-media as
Exam code:9618
Wired vs wireless
What is a wired network?
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A wired network is a network where physical cables are used to join devices together and transmit data
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Computers can be connected to networks using many different types of wires to transmit data
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The most common types of cables in a wired network are:
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Ethernet
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Fibre optic
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Copper
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Advantages & disadvantages of wired networks
|
Advantages |
Disadvantages |
|---|---|
|
Speed – Fast data transfer |
Portability – Can’t move easily, location is limited by physical cable |
|
Security – Better physical security |
Cost – Need more cables to add a new device |
|
Range – High (up to 100m), less susceptible to interference |
Safety – Cables can be trip hazards, need routing along walls, under floors |
What is a wireless network?
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A wireless network is a network where connections are made using radio waves to transmit data through the air
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The most common types of wireless connections are:
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Wi-Fi
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Bluetooth
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What is Wi-Fi?

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Wireless fidelity (Wi-Fi) is a common standard for wireless networks
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Wi-Fi is common in most homes and offices to connect devices such as laptops, tablets & smart phones
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Using Wi-Fi, devices communicate with a wireless access point (WAP), which can be a standalone device or built into a router or switch
What is Bluetooth?

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Bluetooth is another common standard for wireless networks
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Bluetooth is common in most homes and offices to connect devices such as headphones, controllers, keyboards & mice
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Bluetooth is used typically for a direct connection between two devices
Advantages and disadvantages of wireless networks
|
Advantages |
Disadvantages |
|---|---|
|
Portability – Easy to move around, location is only limited by range |
Speed – Slower data transfer than wired |
|
Cost – Less expensive to setup and add new devices |
Security – Less secure than wired |
|
Compatibility – Most devices are manufactured with a built in wireless adapter |
Range – Relies on signal strength to the WAP, signals can be obstructed (up to 90m) |
Types of media
What is transmission media?
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Transmission media is the type of cable used in wired connections
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Wired connections offer a higher bandwidth than wireless connections
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The main options for transmission media are:
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Twisted pair
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Coaxial
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Fibre-optic
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Twisted pair
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Carries electrical signals between devices on a local area network (LAN)
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Common in offices and homes to connect devices such a desktop computers & servers
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Allow duplex communication
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Slower transfer rate compared to coaxial and fibre-optic
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Can suffer from external interference (electromagnetic radiation)
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Low cost

Coaxial
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Used in telecommunication to transmit voice signals, forming the traditional landline phone network
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Adapted to deliver network traffic on a wide area network (WAN) making the internet possible
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Degrades over time which limits their range compared to fibre optic
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Suffers from interference which can disrupt data quality
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Transmits data at a much slower rate, and has a much lower bandwidth compared to fibre optic

Fibre optic
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Uses light to transmit data on a wide area network (WAN)
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Transmits data at high speed and has a higher bandwidth compared to copper cables
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Does not suffer from interference which makes them the most secure option to send sensitive data
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Can cover a long distance without any degradation, they can span cities and countries

Quick comparison
|
Feature |
Twisted pair |
Coaxial cable |
Fibre optic |
|---|---|---|---|
|
Used for |
LAN connections in homes/offices |
Voice signals (telecoms), early WAN/internet |
High-speed WANs, internet infrastructure |
|
Data transfer method |
Electrical signals |
Electrical signals |
Light signals |
|
Speed |
Slower than coaxial and fibre |
Slower than fibre |
Fastest |
|
Bandwidth |
Low to medium |
Lower than fibre |
Highest |
|
Signal degradation |
Moderate |
Degrades over time |
Minimal degradation – works over long distances |
|
Interference |
Prone to electromagnetic interference |
Also suffers from interference |
No interference – more secure |
|
Communication |
Allows duplex communication |
Supports duplex (but lower quality) |
Full duplex |
|
Cost |
Cheap |
Medium cost |
Expensive |
|
Typical use |
Desktop PCs, printers, servers in LANs |
Traditional phone lines, early internet connections |
Modern internet backbones, long-distance data transmission |
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