1. Hardware failure
2. Corrupted software files
3. Hacking into the system
4. Power failure

The organisation of files is in a hierarchy/tree structure
A node is either a folder/directory/sub-folder/sub-directory or the file itself
The top node/folder/directory/drive is the root

(a)

• Hardware required by each computer to connect to a network is a Network Interface Card / NIC / network adapter

(b)

• Computer A adds computer D’s address to packet
• Computer A sends packet to switch
• Switch looks at address on packet  Switch compares to stored list of addresses on network
• Switch forwards packet to computer D’s address

• loss of jobs as some traditional shops/banks close
• lower profits for companies that do not get involved with e-commerce
• decline of leisure shopping as goods are bought on-line
• city centres becoming deserted as shops/banks close down
• gap between rich and poor widening as richer get savings from
• shopping on-line
• more people choosing to interact with computers rather than people
• increase in small businesses
• less pollution/travelling

•  It does not have declaration part
• It does not  have control structures

Advantages

• It is intuitive
• Easy to navigate
• Uses menus, pointers and icons thus easy to learn and use
• It lets the user exchange data between different software applications
• The user does not have to learn complicated commands

Disadvantages

• Takes a lot of memory
• A lot of processor power is needed
• Takes up a larger amount of hard disk space than other interfaces
• They need significantly more memory (RAM) to run than other interface types

https :  protocol

google.co.ke: domain name

/index.html: webpage/file name

1. Application
2. Presentation
3. Session
4. Transport
5. Network
6. Data link
7. Physical

– if one station/cable fails, others are not affected
– easier to identify faults when using star topologies
– it is easier to expand this type of network
– performance doesn’t deteriorate under load

• The number of FDE cycles run per given time/second
• the frequency that the clock ‘ticks’
• 3.8 billion cycles/instructions per second

• Object code refers to a program in machine language while source code to a program in a high level language that must be translated to object code for it to be machine readable

• Better/improved traffic flow control
• reduces accidents
• keeps delays to a minimum
• reduces pollution
• cars use less fuel

Memory management

• Manage the computer’s memory;
• It can control which parts of the memory are being used by which process

Processor management

• Manage the computer’s processor(s)CPU;
• Schedules of which processes are to be executed;

Input/output management

• Manages input/output devices;
• Interacts with/manages/handles the (automatic) installation of device drivers;
•  Handles peripheral device interrupts;
• the computer can communicate with the outside world;
• Control network communication;
• Allow devices to send and receive data;

Managing storage

• Manage secondary storage devices;
• Loading data and programs into the computer’s memory;
• Storage space management (disk quotas);
• To ensure that storage space is allocated fairly and efficiently to specific tasks\users;

Managing security

•  User authentication;
• To make sure that users must prove who they are to access the system;
• Protect against malware;
• Block access to specific vulnerable operations or system areas. For example, software can only be installed with admin access;

Managing applications

• Control access to applications;
• Prevent users or processes from using unauthorised programs // allow users or
• processes to use authorised programs;
• Control application access;
• Prevent/allow an application access to data (or devices);

• It dictates the speed at which data is transferred between these components and enables the sequential execution of instructions in the correct order.
• generates a timing signal that is used to synchronize communication between CPU components and the rest  of the computer system

• connects different networks
• transfer data packets from source to destination
• allow hosts on different networks to communicate

Cloud computing refers to the delivery of on-demand computing resources over the internet. Instead of relying on a local server or personal computer, cloud computing allows users to access and utilize a wide range of computing services and resources hosted on remote servers.

• Sarah could keep all of her files in the cloud and easily access these with her devices. This way she does not have to keep different version on her desktop and laptop.
• Flexibility she could access the files from other devices such as the library etc.
• Disaster recovery if she accidently dropped or damaged a device – all files would be easy to access.

• confidentiality - The principle of protection from unauthorized access or disclosure
• Integrity - the principle of ensuring that unauthorized or undetected changes to data or system configurations do not occur.
• Availability - the principle of ensuring that data and services remain accessible to authorized users at all times

• A HDD can contain multiple platters (disks);
• A disk/disks that move/spin
• Each platter is divided into sectors;
• The disks are spun at a very high speed (approximately 7,200 rpm to 10,000 + rpm);
• Read\write heads (move across the disk to) read and write data;
• There is one read\write head for each side of a platter ie two heads per platter;
• Data is written to\read from the disk by magnetising\polarising\sensing microscopic regions on the disk;
• Data is organised in concentric rings called tracks;
• There is a small circuit board on the drive that controls the reading and writing of data;
• Data is transferred from and to the disk via a cable/electrical current being passed;
• The intersection of sectors and tracks are called blocks;
• Data is read 1 block at a time

 Data

Instructions