1. aaa Grade 10 - Term 1 – Revision Notes 2017 - 2018
Computer Science
Grade 10 - Term 1 – Revision Notes

2. Unit 2 – Networks in our daily life
Word
Meaning
Cell
the geographic area in which an individual tower can provide a signal to a phone.
GPS
the Global Positioning System network uses satellites to transmit signals that cover the globe.
Hotspot
an area where wi-fi signals are available.
NFC (Near Field Communications)
wireless communication technology that helps data exchange by devices very close to each other.
Ethernet
technology commonly used in local area networks.
Network Interface Card (NIC)
hardware that enables the device to connect to the network medium, either wired or wireless.
Physical Topology Diagram
records where each host is located and how it is connected to the network; it shows where the wiring is installed and the locations of the networking devices that connect the hosts.
Logical Topology
it shows the relevant network configuration information, such as IP address.
Twisted-pair
wires are grouped in pairs and twisted together to reduce interference.

3. Word
Meaning
Coaxial Cable
cable used by cable TV companies; made of either copper or aluminium copper.
Fibre-optic Cable
can be either glass or plastic; carries digital information at very high speeds over long distances.
Crosstalk
source of interference occurs when cables are bundled together for long lengths.
Straight Through Cable
type of UTP cable that has the same termination pattern on both ends of the cable.
Cross Over Cable
type of UTP cable that has the transmit and receive wires reversed on one end of the cable.

4. Mobile Telephones
Different types of networks GPS The Global Positioning System network uses satellites to transmit signals that cover the globe. The smart phone can receive these signals and calculate the phone’s location to an accuracy of within 10 meters. Wi-fi Wi-fi transmitters and receivers in the smart phone enable the phone to connect to local networks and the internet. In order to receive and send data on a wi-fi network, the phone needs to be within the range of the signal from a wireless network access point. wi-fi networks are usually privately owned but often provide guest or public access hotspots. A hotspot is an area where wifi signals are available. Wi-fi network connections on the phone are like the network connections on a laptop computer. Bluetooth A low-power, shorter-range wireless technology. It is intended to replace wired connectivity for accessories such as speakers, headphones and microphones. Because Bluetooth technology can be used to transmit both data and voice, it can be used to create small local networks. NFC NFC stands for Near Field Communications. NFC is a wireless communication technology. It enables data to be exchanged by devices that are very close to each other, usually less than a few centimeters.

5. Network Components
1. Hosts send and receive traffic. A host is a generic name for most end-user devices. A host has an IP network address.
Examples of hosts are personal computers, network-attached printers and even your phone.
2. Networking devices connect other devices, mainly hosts. These devices move and control network traffic.
Examples of network devices are hubs, switches and routers.
3. Network media provides connections between hosts and network devices. Network media can be wired – copper or fibre-optic, or use wireless technologies.

6. Network Interface Card (NIC).
This is a network interface card (or NIC) which is required to connect a computer to a network.
Each Ethernet NIC has a unique address permanently embedded on the card. It is known as a Media Access Control (MAC) address.
A cable is inserted into a connector (or port) on the network interface card so that the computer can be attached to a network.
A wireless network interface card can be used to connect a desktop computer to a network. Radio waves are used to provide a link to a wireless

7. Connecting end-user devices
There are three parts to the IP configuration. They must be correct for the device to send and receive information on the network:
IP address – identifies the host on the network
Subnet mask – identifies the network on which the host is connected
Default gateway - identifies the networking device that the host uses access the internet
Commands used to check IP configuration
Ipconfig  used to display all the IP configuration values
Ping to check for the network end-to-end connectivity between two devices.

8. Manual and automatic address assignment
Manual IP configuration and dynamic IP configuration
Manual IP configuration
With manual configuration, the required values are entered into the device via the keyboard.
The IP address entered is referred to as a static address.
It is permanently assigned to that device.
It never changes unless the admin logins in and changes it.
Dynamic IP configuration
Most end-user devices can be set up to receive network configuration automatically.
This enables the device to request an address from a pool of addresses.
They are assigned by a Dynamic Host Configuration Protocol (DHCP) server.

9. Private and Public addresses
There are two types of IP addresses; public and private.
Public addresses are addresses which are globally set from your ISP (Internet Service Provider), like Du or Etisalat.
Private IP addresses are set by the network administrator for a DCHP server. They are for your internal LAN network. As these are local personal addresses you and your neighbour could share the same private IP address because in theory they are two different networks (two different routers two different houses).

10. Network topologies and representations Physical and Logical topologies
Physical topology
When networks are installed, a physical topology diagram is created.
It records where each host is located and how it is connected to the network.
It also shows where the wiring is installed and the locations of the networking devices that connect the hosts.
Such a diagram uses symbols or icons.
Logical topology
This information cannot be “seen” from the physical view of the network.
The device names, IP addressing, configuration information are logical pieces of information.
They may change more often than the physical connectivity.

11. Network diagram

12. Logical diagram
Draw and label all the parts. Make sure you put the correct media/cables. Learn how to write the IP addresses.

13. Unit 4 - IPv4 Address and subnet masks
A host needs an IPv4 address to work on the internet
Every device on the internet has a unique IP address
IP addresses are either 32-bit or 128-bit numbers. The 32 bits are grouped into four 8-bit bytes called octets.
The address is broken down into four 8-bit numbers (each is called an octet)
There are currently two different versions of IP addresses in use—IPv4 and IPv6.
IPv6 is so much larger than IPv4,
It is very difficult for humans to read a binary IPv4 address. For this reason, the 32 bits are grouped into four 8-bit bytes called octets. Each octet is presented as its decimal value, separated by a decimal point or period.
This is referred to as dotted-decimal notation.
The router is the interface to the internet with the public address.
Network Address Translation (NAT) is used to translate between private IPv4 and public IPv4 addresses.
This is usually done on the router that connects the internal network to the ISP's network.

14. Networks and hosts
There are two parts to every IPv4 address. How do hosts know which portion is the network and which is the host? This is the job of the subnet mask.

15. 5. Providing Network Services
Word
Meaning
Protocol
a set of rules and guidelines for communicating data between network devices
Domain Name System (DNS)
an internet service which translates domain names into IP addresses
Secure Shell (SSH)
a protocol that provides administrators with a secure way to access a remote computer
Simple Mail Transfer Protocol (SMTP)
a protocol used for standard electronic mail transmission between servers
Post Office Protocol (POP)
an application layer protocol used by local clients to receive s from remote server over TCP/IP connection
Internet Message Access Protocol (IMAP)
an internet standard protocol used by a client’s to retrieve s from the mail server over a TCP/IP connection
Web Server
a program that uses HTTP to serve the client web pages in response to their requests
File Transfer Protocol (FTP)
a standard network protocol on the network; used for the transfer of computer files between client and server

16. Word
Meaning
HTTP
Hyper Text Transfer Protocol is an application protocol for transferring files like text, graphics, images, sound, video and multimedia files.
HTML
Hyper Text Markup Language is a standard markup language used for creating web pages and web applications
Web Page
a document commonly written in Hyper Text Markup Language; accessible using internet browsers
Client
the requesting user or program in a client/ server relationship
Server
a computer designed to process the requests from clients and deliver data to clients over a local network or the internet
Port
a process-specific or applicationspecific software construct serving as a communication endpoint used by different protocols
Port Number
a numerical number assigned to a specific port; usually a 16-bit unsigned number that ranges from 0 to 65535
Telnet
Telecommunication Network protocol uses access remote computers over TCP/IP; used to provide bidirectional, interacted, text-oriented communication using virtual terminal connection
Optical Signals
transmission achieved by converting the electrical signals into light pulses

17. Server Job The server typically looks after: Logins and security
File handling
Printing
Internet access

18. Uniform Resource Locator (URL)
The URL identifies the:
The protocol that is being
used to send the request
(this can also be https, or ftp)
The domain name is example.com -
sent to the DNS server for resolution to an IP address
The folder location on the web server
where the resource is stored
The actual resource
or file that is being
requested

19. Domain Name Service (DNS)
Each server has an IP address. To access the resource your computer must find the IP address of the server. It finds this using a service called DNS, Domain Name Service. DNS is like a phone book for the internet. DNS working steps is as follows:-
Step 1: Request information
Step 2: Ask the DNS servers
Step 3: Ask the root nameservers
Step 4: Ask the authoritative DNS servers
Step 5: Retrieve the record

20. Few Examination Tips You are given 35 minutes to complete the exam.
Allocate time according to the sections.
- Read the questions carefully.
- Look for key words in the question like define, explain, list, describe. Answer accordingly.
- Do not forget to Label your drawings.
- See the marks allotted and answer accordingly Do not leave any answer blank. Try to attempt all questions.
ALL THE BEST 