GCSE AQA Computer Science 9-1 Paper 2

  • Created by: HannahDav
  • Created on: 04-04-18 08:10

Computer Networks-The Internet

  •  The internet is the largest and most famous WAN. 
  • It is a collection of interconnected networks- it is a worldwide connection of computers and networks owned by no-one
  • Websites are stored on web servers connected to the Internet and each site has unique web address so that it can be accessed 
  • All information on the world wide web is stored in documents known as web pages, accessed using web browsers. E.G. Google chrome
  • The Web is just one form of communication over the internet. The Internet is also used for email and instant messaging.
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Computer Networks-WANS + LANS

Wide area networks:

  • A collection of computers and networks using resources supplied by “third party carrier” over large geographical area.
  • Uses cables, telephone lines, satellites and radio waves to connect components 
  • Tend to be under collective or distributed ownership due to the high cost of the system

Local area networks:

  • Network over small geographical area consisting of collection of computers and peripheral devices.
  • Usually owned and managed by single person or organisation
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Data Transmission+Packet switching

  • Every device that can connect to the internet has a separate and unique IP address
  • The IP address of a mobile device can change as its physical location is needed to to receive communications
  • Suppose you want to send a file of 3Mb across the Internet. The file will be broken down into “data” packets of 512 bytes. Each packet is given a header containing: The IP address of where it going, the IP address it has come from, sequence number of packet, number of packets in whole communication and error checking data. Packets are then sent to their destination along different routes before being reassembled.
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Computer Networks-Network Hardware

 

  • Router: Designed to route packets across WAN. Acts as a node and packets passed from router to router to destination. If packet destined for computer in LAN, there will typically be a router to a switch.
  • Switch: Component of a LAN that knows MAC addresses of connected devices. Will send packets only to the intended recipient using MAC address.
  • Network interface card(NIC): Required to connect any network-enabled device. Physical component. Wireless or wired using ethernet cable. 
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Computer Networks-MAC addressing

  • Each NIC has a Media Access control address assigned by manufacturer 
  • Devices can have more than one- one for wired ethernet and another for wireless or bluetooth 
  • 48bits, written in twelve hex digits- first six digits identify manufacturer and the second six the serial number of the device. The address in unchanging 
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Computer Networks-Wireless Networking

  • Many networks use WI-FI (a family of protocols allowing wireless networking to run smoothly) connections rather than physical wires
  • Advantages:
    • Users can move around more freely than with wired
    • Users can share files and other resources without being connected to port
    • Saves expense, time and inconvenience of installing cables through walls
    • It is easier to add new devices as no new cabling required
    • Instant transfer of data is much quicker than wired
  • Disadvantages:
    • File transfer speeds generally slower than wired
    • Connections can be obstructed by walls, ceilings and furniture 
    • Generally less secure and easier to hack into than wired
  • Risks of wireless networks:
    • Criminal activity: unauthorised user can use wireless connection to hack into network+plant viruses or halt network by flooding it with traffic
    • Bandwidth stealing: by using internet connection to download music, games and other software, outside intruders can slow network down
    • Confidentiality: if any information not encrypted before transmission, intruders can gain access to confidential information
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Advantages+Disadvantages of Networking

  • Advantages:
    • Folders+files can be stored on file server so can be accessed by authorised users from any computer on network 
    • Peripheral devices can be shared. E.G. printers and scanners
    • Internet connection can be shared and any authorised user on network can use email
    • User profiles and security can all be managed centrally
    • Software can be distributed across network rather than installing individually 
    • All files can be backed up centrally
  • Disadvantages:
    • If file server goes down no files can be accessed
    • Network faults can lead to loss of data
    • As network traffic increases, performance degrades so accessing resources might be slow 
    • Difficult to make system secure from hackers
    • Viruses may be able to infiltrate system
    • The larger the network becomes the harder it is to manage
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Computer Networks-Topologies

Star:

  • Advantages:
    • If one cable fails, all other devices continue to function
    • Consistent performance even when network heavily used
    • Good security as data received only by node for which intended
  • Disadvantages:
    • Can be costly to install due to lots of cabling
    • If server or central switch fails, entire network collapses

Bus:

  • Advantages:
    • Easy and inexpensive to install- less cabling than star
    • No reliance on central node
  • Disadvantages:
    • If main cable fails then whole network goes down
    • Cable failures are hard to isolate because all computers in network affected
    • Performance slows as traffic increases
    • Low  security as every node can see all the transmissions
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Computer Networks-Ethernet

 

  • Refers to a set of networking protocols widely used in LANs
  • It describes how devices should format data ready for transmission between devices on network:All new computers have Ethernet built in. 
    • Nodes will wait until the connection is quiet before attempting to transmit
    • Two nodes attempting to transmit at the same time will stop and each will wait a random period before reattempting 
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Computer Networks-Transmission media

Transmission media:

  • Fibre optic cables transmit data as light. They are high performance+expensive cables-they don't suffer interferences+can transmit very long distances at high bandwidth without loss of signal quality
  • CAT 5e+CAT6- common ethernet cables, contain copper wires which are twisted together to reduce internal interference. Cheaper than fibre optic cables+ have decent bandwidth so they are commonly used in homes and offices on a LAN
  • Coaxial cables-single copper wire surrounded by a plastic layer for insulation and a metallic mesh which provides shielding from outside interference. Cheap but have low bandwidth.
  • Bandwidth=amount of data that can be sent across network in a given time.

Ethernet transmission:

  • Ethernet systems divide data into frames- each contains source and destination MAC addresses and error checking data
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Network Security-Keeping Networks Secure

  • Authentication: checking for genuine, identified users. E.G password protection and user access levels.
  • Encryption: protect data by scrambling it using a key. Can only be decrypted by someone with the key.Firewall: designed to prevent unwanted internet traffic from gaining access to the LAN. Unauthorised users external to the network are blocked.
    • Plaintext: the original message to be encrypted
    • Cipher text: encrypted message
    • Encryption: the process of converting plaintext to cipher text
    • Decryption: the process of converting cipher text to plaintext
    • Key: a sequence of numbers used to encrypt or decrypt 
    • Encryption algorithm: the method for encrypting the plaintext
  • MAC address filtering: the use of MAC addresses to define which devices can gain access to a network
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Network Protocols

  • A protocol is a set of rules that defines how devices communicate

Ethernet protocol:

  • Family of related protocols 
  • Ethernet stations communicate by sending one another data frames, individually sent and delivered, each ethernet station has a 48-bit MAC address which specifies source and destination of frames
  • Now so universally used that most manufacturers build Ethernet interfaces directly into PC motherboards, decreasing the need for NICs

Wi-Fi:

  • Technology that allows devices to connect to a WLAN 
  • Wi-Fi compatible devices can connect to the internet via a WLAN and Wireless Access Point (WAP)
  • The WAP receives data from a network via its physical connection, the transmitter then converts this data into radio waves which are then transmitted, any device on the network receives the radio signal via a Wi-Fi adaptor which allows it to communicate or download data from the data source
  • This also works in reverse direction
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Network Protocols

User Datagram Protocol (UDP):

  • Computer applications send messages referred to as datagrams to other hosts on an IP network. Alternative to TCP but has no error checking or correction
  • Also maintains an open connection between the sender and the recipient thus, two-way communication is often faster-uses in gaming

Hyper text transfer protocol (HTTP):

  • Used for accessing and receiving web pages in the form of HTML files on the internet
  • The protocol requests the web server to transmit the requested web page to the user’s browser for viewing 
  • The secure version of HTTP is HTTPS, it encrypts the data so it cannot be understood if hacked

File transfer protocol (FTP):

  • Used when transferring computer files between a client and a server on a computer network 
  • Based on client-server model and uses separate control and data connection between the client and server 
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Network Protocols

Internet messaging access protocol (IMAP):

  • Email protocol that stores email messages on a server but allows users to view and manipulate the messages as though they were stored locally on their own computers
  • Messages can be flagged, be put into folders and drafts saved

Simple mail transfer protocol (SMTP):

  • Protocol used for sending e-mail messages between servers, the messages can then be retrieved by an e-mail client using either POP or IMAP
  • Used for sending out and forwarding mail from one server to another 

Transmission Control Protocol (TCP):

  • Alternative to UDP- send acknowledgements when all packets of a file have been received.
  • Resends any packets that are not received
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TCP/IP Model

  • Application layer: Network applications (web browsers, email programs, etc) operate here. The data being sent is encoded so that it will be understandable by recipient. This means formatting data and adding an appropriate header according to a protocol being used. E.G. HTTP or FTP
  • Transport layer: sets up the communication between the two hosts and establishes settings such as “language” and size of packets. It splits the data into packets and adds packet information such as, the packet number to specify the packet’s order and total number of packets so they can be reassembled correctly. It hides different network technologies and architectures. TCP and UDP operate on this layer.
  • Network/internet layer: Addresses and packages data for transmission and routes packets across network.Attaches IP address of the sender so the recipient will know who sent it. Also attaches the destination IP address. IP operates in this layer.
  • Link layer: where network hardware such as, NIC is located. OS device drivers also sit here. It attaches MAC addresses of the sender and recipient, allowing packet to be directed to a specific device on a LAN, for example.
  • Packets of data are passed down through the layers which each perform their individual functions before it is transmitted across the network. At the receiving end, the packets are then sent back up through the layers to the application they are intended for
  • The advantage of using layers is that each is self-contained, communication over the internet is broken down and having enforced set of rules on each layer forces companies to lake compatible software.
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Cyber Security-Threats

  • Removable media
  • Outdated/Unpatched software
  • Simple and default passwords
  • Misconfigured access rights
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Cyber Security-Social Engineering

Art of manipulating people so they divulge personal information

Blagging:

The act of recklessly or knowingly obtaining or disclosing personal data or information without the consent of the controller. E.G. dishonest employee convincing another employee to disclose data such as their password, claiming they need to install new software on their device. To prevent this companies should ensure that security training is provided to employees.

Phishing:

Emails designed to steal money, get login details or steal identity. You may receive an email with a link asking you to verify or enter bank account details. If you click on the link a hacker may be able to access your contact list. They can then send emails to others asking for money in desperate situations. To prevent this you should always be aware of poor grammar, suspicious content and email your friends back if in doubt verifying their emails.

 

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Cyber Security-Social Engineering

Pharming:

Technique used to redirect website’s traffic to another, fake site. Attacker will put code on hard drive or code itself  and when you arrive on website you will be asked to disclose personal details. Major concern for online banking + e-commerce.

Shouldering:

Physical technique used to obtain passwords and personal data. E.G. watching someone type in PIN for bank account

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Cyber security-Malicious Code

Malware:

  • Refers to a variety of forms of hostile or intrusive software
  • Computer virus:
    • Program installed on computer with your knowledge or permission with the purpose of doing harm
    • Includes instructions to replicate automatically on computer and between computers. Can be harmful to data or just annoying.
  • Viruses can be spread through email or instant message attachments or through files, programs alongside games downloaded from web page

Spyware:

  • Gathers data in secret without consent of user. Often used to track and store users’ movements on internet. It is not illegal and is used by many companies 
  • The data gathered is often used in adware

 

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Cyber security-Malicious Code

Adware:

  • Analyses which internet sites a user visits and then presents adverts for products a user is likely to want
  • Mostly legal and used by large companies. Anti-adware available however, companies have sued such technology in past

Trojan:

  • Program claiming to have one function but really has another. You may be invited to click on link for a legitimate process or reason but really another process is occurring. For example, spreading viruses or giving controller unauthorised access to your device
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Detecting Cyber Security Threats

  • Network forensics involves capturing, storing and analysing network events.Using special software, network managers can can look at business transactions to verify they are not fraudulent or stop a security attack before it bring network to grinding halt. It also detects data leaks and where confidential data is going to an external source
  • Penetration testing: used to find security risks in a system.
    • Black box penetration test: testers given little or no information about network. Could target email servers, web servers or firewalls. Objective is to see if hacker can get in and once in what damage they can do.
    • White box penetration test: tester given basic network information such as IP addresses, passwords and network protocols. Aims to determine how much damage dishonest insider could do.
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Preventing Vulnerabilities

  • Anti-malware software: will protect computer in three ways:
    • Prevents harmful programs being installed on computer
    • Prevents important files(E.G. operating system) from being changed or deleted
    • If virus does install, software will detect in one of its regular scans. Any virus detected will be removed
    • Must have constant updates from internet as viruses often updated
  • Automatic software updates: popular software is common malware target. Allowing automatic updates will remove vulnerabilities and harmful code placed in software by hackers
  • Biometrics: use of biological characteristics to secure data or information. Probably of two people having same biological characteristics is low so secure. Often used in mobile devices. E.G fingerprint or voice patterns
  • CAPTCHA: “Completely Automated Public Turing test to tell Computer and Humans Apart”- test to see if user is human or not using undecipherable code
  • Email to confirm user identity: when you sign up to a new web service you may be asked for email confirmation as this provides more certainty of user identity. 
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Binary Logic and Logic Gates

  •  Boolean variables are either true or false where 1 represents true and 0 false. This can be used to represent whether electronic circuits are open or closed.

The gates:

AND:

  • A*B-written as A .B

NOT:

  • Not A/inverted input of A 

OR:

  • A+B- written as A+B
  • Many logic gates combined together can form a logic circuit. These circuits form the foundation of many modern circuits such as computer memories and household devices
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Units

Unit-number of bytes-decimal value

Byte-8bits-1

Kilobyte-10^3-1000

Megabyte-10^6-1,000,000

Gigabyte-10^9-1,000,000,000

Terabyte-10^12-1,000,000,000,000

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Binary to Decimal Conversions

  • To get from binary to decimal, simply add up all the numbers with one above them. E.G. below would equal 182
  • To get from decimal to binary simply see if the above numbers go into the number, if so place 1 in that column.

10110010

= 132+32+16+2=182

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Addition of Binary Numbers

00110110+

00100110=

01011100

  • To add binary numbers you must place the numbers underneath one another: two ones make 0 and the 1 is carried to the next number. 0 and 1 makes 1. When adding three binary numbers, method is the same except you add first two then add the third to the result. 
  • Overflow:The biggest number you can represent with 8 bits is 255- if you add two binary numbers together that result in a number greater than 255, it will need nine bits to be stored. A computer stores things in memory in finite amount of space. If you cannot represent the number in that amount of space due to it being too large then overflow occurs
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Binary Shifts

  • Shifting a binary number to the left multiplies the number by 2, for example, a binary shift of three places to the left would give n x 2^3
  • Shifting a binary number to the right divides it by 2, for example, a binary shift four places to the right would give n/2^4 
  • Can result in loss of accuracy if you shift and numbers are removed from the end 
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Hex

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Hex Conversions

(http://www.matrixlab-examples.com/image-files/binary_to_hexadecimal_001.gif)

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Hex Conversions

  • Decimal to hexadecimal:
    • First step os to work out how many groups of 16 go into decimal number. E.G. 182/16 = 11 remainder 6. 11=B in hexadecimal so hex number is B6.
    • Alternatively you could convert decimal into binary first
  • Hexadecimal to binary:
    • Simply convert each hex digit into a group of 4 binary digits.
    • E.G. A7= 10100111
  • Hexadecimal to decimal:
    • Multiply heading or place values by the hex digit.
    • E.G. A7= (10x16)+(7x1)=167
  • Uses of hexadecimal:
    • Easier to understand+remember than binary numbers so often used in place of binary digits. E.G. picking colours for graphics
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ASCII

  • Every time character is typed, code transmitted to computer+stored in binary
  • PCs sometimes use character set of American Standard Code for Information Interchange
    • Uses 7bits to code each character- biggest number that can be held is 1111111(127 in decimal). Therefore, 128 characters can be represented in ASCII character set using codes 0 to 127
  • Character codes are grouped+run in sequence. E.G. if ‘A’ is 65 then ‘B’ must be 66.This pattern applies to other groupings such as digits and lowercase letters.
  • ASCII code value for 5 is 00110101 is different from pure binary value for 5-00000101. This is why you cannot calculate with number which are input as strings
  • Extended ASCII code:
    • Stores each character using 8 bits which gives an additional 128 characters (2^8 or 256). The extra characters represent characters from foreign languages and special symbols.
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Unicode

  • New standard for representing the characters of the languages of the world 
  • Uses between 8 and 32 bits per characters and has advantage that it can represent many more unique characters than ASCII because of the larger number of bits available to store a character code. It uses the same codes as ASCII up to 127
  • Major advantage is that it provides a unique standard for all the world’s writing systems. It allows for multilingual text in any language
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Images

  • A pixel is a single point in an image which can have its colour set independently. If the size of an image is increased then more pixels will be stored.
  • The number of bits per pixel is referred to as the colour depth, to work out the minimum required colour depth from the number of colours in the image, convert the number of colours to a power of 2
    • E.G. 8= 2^3 colours- 3 bits required
    • 256=2^8 colours-8 bits required
  • If colour depth is increased more bits are used to represent each pixel and the overall size of file will increase
  • Colour depth=number of bits to represent each pixel. The higher the number of colours, the more faithful the image will be, also affects size of the image 
  • Size of image=number of pixels or dots that make up an image. Greater number of pixels per inch (PPI)=sharper the image will be+ larger size of file. PPI(pixel density) used yo describe the resolution of a computer screen, camera or scanner

In bits: (width x height x colour depth)/8 (bytes)

 

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Sound

  • Sound waves are analogue(continuously changing), this means that to be stored into a digital file were the waveform is a series of binary numbers. The device that takes real life sounds and converse them into digital representation is called an Analogue-to-Digital Converter(ADC)
  • The analogue signal is converted as follows:
    • 1. Analogue sound received by microphone
    • 2. Converted into electrical analogue signal 
    • 3. Signal amplitude measured at regular intervals(sampled)
    • 4. Values rounded to a level (quantisation)
    • 5. Values stored as series of binary numbers 
  • Sample= Measure of amplitude at point in time
  • Sample resolution=number of bits to store each sample
  • Sample rate= the frequency with which you record the amplitude of the sound or number of sample per second-measured in hertz
  • Calculating size of sound file: sample rate x sample resolution x number of seconds
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Compression

  • The process of reducing the size of a file to reduce amount of storage they take, allow large files to be transmitted as email attachment and increase transmission time
  • Lossy: encoding method where times are compressed by removing some of the detail. Used to compress images, audio files and video files. E.G.JPEG.
  • Lossless: encoding method where times are compressed but no data lost, essential for data and text files. For example, zipping a file.
  • Run Length Encoding: simple form of lossless compression. Runs of data are stored using frequency/data pairs. Not so useful for files that don't have many runs and can actually increase file size. Most useful on simple images containing many pixels of the same colour.
  • Huffman coding: Compression technique used to reduce the number of bits used to represent each letter. The more frequently a letter appear in the text, the fewer bits are used to represent it in a text file. E.G. the work ‘not’ would require 4+5+4=13 bits to store. In ASCII 7x3=21 bits would  be required. 
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Von Neumann

  • The very computers could not store programs and had to input by setting switches 
  • In the 1940s John Von Neumann developed the concept of the stored program computer in the 1940s. In the Von Neumann architecture:
    • program is stored in main memory and instruction fetched and executed sequentially
    • there is a single memory for accessing both data and programs 
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The CPU

The brain of the computer system-stores all data+instructions that makes computer work

  • Arithmetic Logic Unit(ALU): carries out logical operations, shift operations and arithmetic operations
  • Control unit: coordinates all activities taking place inside CPU. Functions can be summarised as follows:
    • Controls execution of instructions in correct sequence
    • Decodes instructions 
    • Regulates+controls processor timing using regular pulses from system clock
    • Sends+receives control signals to and from other devices within computer
  • Clock: controls processor timing, switching between 0 and 1 at rates exceeding several million times per second. Synchronises all CPU operations.Clock frequency is number of clock cycles which occur each second
  • Bus: internal connections which pass data between components of CPU. On top of ALU, control unit and clock, there are several fast memory locations called special-purpose registers which are involved in fetch-execute cycle. Data and instructions are passed between registers and components alongs these buses (referred to collectively as the bus)
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Fetch-Execute cycle

  • To run the program the processor fetches an instruction, decodes it and then executes it. The processor executes one instruction at a time. This is called the fetch-execute cycle.
  • In the fetch part of the cycle:
    • The address A of the next instruction to be executed is fetched from the register where it is held
    • The register is incremented so it points to the next instruction to be fetched
    • Instruction at address A is fetched from memory and put into special register ready to be decoded
  • In decode part of the cycle:
    • The control unit decodes the instruction to see what has to be done next
  • In the execute part of the cycle:
    • Instruction is executed.
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Factors affecting CPU performance

  • Clock speed: all activities begin on clock pulse but some take more than one clock cycle to complete. Clock speed is measured in hertz and for modern computers GHz, typical speeds for PC are between 2 and 4GHz. The greater the clock speed the faster instructions will be executed.
  • Type and size of cache memory:small amount of fast memory used to improve speed where frequently used instructions or data can be stored temporarily. Intermediary between RAM and CPU that makes any frequently used data available much faster. As main memory has to be accessed less often the processor can work faster so CPU performance increases. Computers have far more RAM than cache. There are different levels of cache:
    • Level 1: extremely fast but small(2-64KB)
    • Level 2: fairly fast and larger(256KB-2MB)
    • Some CPUs also have level 3 data cache 
  • Processor cores: Multiple cores could work on different programs that operate in parallel but unless the program is designed to use multiple cores is isn't necessarily luck faster. On the whole however, a computer with a multi-core processor will function faster than a single-core processor when performing multiple tasks
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Memory-ROM+RAM

ROM:

Non-volatile: no data lost when is turned off

Used to store the BIOS/bootstrap loader which is required at start-up of the computer

Memory can only be read from but not written to

RAM:

Volatile: data is lost when power turned off

Stores user data/programs/part of OS currently in use

Memory can be written to or read from

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Secondary Storage

  • Non-volatile
  • Holds much more data than main memory and is relatively inexpensive per MB
  • Slower access speeds than main memory
  • Following should be considered when choosing a storage device:
    • Capacity 
    • Speed
    • Portability
    • Durability
    • Reliability
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Secondary Storage-Magnetic Disks

  • Uses rigid rotating platters coated with magnetic material. Ferrous particles are polarised to become either north or south state, representing 0 or 1.
  • Disk is divided into tracks in concentric circles and each track is subdivided into sectors. Disk spins very quickly at speeds of up to 10,O00RPM.
  • A drive head moves across the disk to access different tracks and sectors. Data is read or written to the disk as it passes under the drive head.
  • A hard disk may consist of several platters each wit its own drive head.
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Secondary Storage-SSDs

  • Used in memory sticks and many portable devices
  • Uses flash memory. They are built from special types of transistors that do not lose their state when the power is turned off. There are two types of flash memory, NOR and NAND which are wired in parallel and series respectively.
  • Both types of SSD use electrical circuits to persistently store data
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Secondary Storage-Optical Devices

  • E.G. CD, DVD and Blu-ray
  • CDs come in three formats: read-only(CD-ROM), recordable(CD-R) and rewriteable (CD-RW). CD_ROM, DVD and Blu-Ray disks are ‘pressed’ with the pits and lands representing the data at time of manufacture
  • Use low powered laser to read the disk by bouncing light onto its surface which is covered in pits and lands. At the point where a pit starts or ends, light is scattered and therefore not reflected so well. A land, and the bottom of a pit reflects the light well. Non-reflective and reflective areas are read as 1s and 0s. There is only one single track on an optical disk arranged as a tight spiral. A recordable disk uses a higher powered laser to change the reflecting properties of a disk and this make lands and pits.
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Advantages and Disadvantages of Secondary Storage

SSDs: Reliable, less susceptible to shock+damage than HDDs as they have no moving parts, Lighter than HDDs, Faster access times than HDDs as they don't spin and data can be accessed instantaneously, Lower power consumption,Run much cooler than HDDs, Currently more costly per GB than HDDs, May deteriorate over time and not last as long as HDDs

Optical: Cheap to produce, Easy to send through post for distribution purposesCan be damaged or corrupted easily by excessive sunlight or scratches 

Magnetic: Inexpensive, very high capacity, internal drives very reliable, Not very portable owing to moving parts so can be damaged easily, Can be corrupted by magnetic fields

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Cloud Storage

  • People are choosing to store data in ‘the cloud’ on an increasing basis- this refers to saving data on an off-site storage system maintained by a third party, E.G. Dropbox. Instead of saving data on your computer’s hard drive or other local storage device, you save it in a remote storage facility and access it via the Internet
  • Advantages: access data from anywhere in the world, share data with other people in different locations, backup no longer such an issue-responsibility of provider to keep data safe
  • Disadvantages- dependent on having Internet connection to access data, some concerned by security and whether their data could be attacked by hacker
  • Usually stored on hard disks but increasing SSDs in remote locations in different countries.
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OS-Memory Management

  • Memory management:all programs running must be in computer’s main memory, the OS must manage where in memory the program+data it needs will go. When you start a program, memory manager allocates it adequate blocks of free space in main memory. Also allocates memory for any data file that you open
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OS-Processor management

  • Processor management: manages the use of processor cores. In a multi-tasking system, E.G. Windows, several tasks may be running at same time. The task manager displays the tasks currently running. The tasks are not actually running at the same time, the OS allocates each one a tiny slice of processor time in turn. Some computers have more than one processing core and in that case the operating system has to allocate tasks to each of them whenever possible.
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OS-Input/Output devices

  • Management of input/output devices: When user gives instruction to print, the I/O management function takes over and controls the sending of the data to be printed from memory to device user. Meanwhile, user can carry on whatever they were doing.
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OS-Application Management

  • Application management: OS will interact with applications through an Application Program Interface(API) which allows the application to communicate with OS. Once installed, application will need to communicate with OS to execute modules, save data, …. The OS will maintain a directory of where each application and each file is stored on disk. When application run, OS will allocate space in memory for it to be loaded and job will enter queue of jobs being allocated processor times.
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OS-Operating management

  • Operating management: includes many methods to ensure safety from threats and attacks. Functions include:
    • Controlling access to a computer by setting usernames and passwords for different users.
    • Setting different access rights and privileges for different users
    • Automatically downloading updates for OS to ensure security loopholes are patched
    • Encrypting files stored on hard disk
    • On a network, the OS security software can also identify all the active users currently on network, manually log out users and monitor how long each user is logged in over a period of time
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Utilities

Utility Software:

  • OS controls+manages  computer system and most also contain utilities
  • Not essential but make it easier for user oh provide housekeeping functionality
  • E.G. security utilities, disk organisation utilities, data compression utilities, etc..

Maintenance Utilities:

  • Disk Defragmentation: Files stored on hard disk in blocks wherever there is space. This means that large files are split into segments and can be separating. This is not efficient as OS has to keep track of where each segment is . Eventually, thousands of segments of files are stored all over hard disk- they become fragmented. Disk defragmenter shuffles segments around to put those from same file together to increase access speed. Also, puts all free space together so new files can be stored in one place.
  • Automatic updating: Makes sure any software on computer is up-to-date, it will regularly check internet from updates which will downloaded+installed if they are newer than version on computer. Firewalls and antivirus software must be regularly updates as new viruses and threats constantly appear.
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Embedded Systems

  • Computers built into other devices and are usually dedicated systems. Often used as control systems-monitoring and controlling machinery in order to achieve desired results.
  • Advantages:
  • Devices easier to use 
  • Very efficient
  • Good reliability
  • Cheap to design and manufacture due to their singular functions
  • Unlike non-embedded systems:
  • System is held in non-volatile memory such as ROM or EPROM and is rarely if ever changed after manufacture
  • Some firmware devices are permanently installed and cannot be changed after manufacture
  • It is not usually possible to upgrade the hardware or attach peripherals 
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Ethical Issues of Technology

Artificial Intelligence:

  • Sci-Fi is full of stories about technology and robots taking over the world 
  • Many feel that the use of robots or programs equipped with AI will decrease jobs and that the development of AI poses a threat to the long term survival of humanity
  • Generally, people don't trust robots to take over roles where lives are at stake. E.G. doctors
  • Under 15% of the population believes they could be friends with robots and 10% believe they could imagine them as family members

Driverless Cars:

  • Robots taking over human roles. E.G. driverless cars
  • Ethical issues: will car be able to distinguish between children and plastic bags? Who is to blame if someone killed?

Designer babies:

  • Proposed use of pre-implantation genetic diagnosis to select the desired traits for the child such as, gender, height or intelligence.
  • Use of genetic screening of embryos prior to birth to detect genetic diseases raises more ethical issues
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Ethical Issues of Technology

Social networking:

  • Some feel we are losing the ability to communicate face to face
  • Dangers, E.G. pedophilia 

Rating culture:

  • Using technology you are able to rate countless people, places and events 
  • Many feel that this is not good and can lead to many problems
  • For example,  the Peeple app launched in March 2016 allows you to rate anyone you come into contact with, providing you allow yourself to be ‘recommended’

Risks of digital technology:

  • 3D printing allows for the printing of things such as, guns
  • Is it ethical for a navigation system to take people through a previously quiet town to reach popular destination for fastest route?
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Legislation and Privacy

Data Protection Act 1998:

  • Anyone who stores personal details must keep them secure. Companies with computer systems that store any personal data must have processes and security mechanisms designed into the system to meet this requirement.
  • Implications on legislation: it is illegal to pass on or sell details of a customer to another organisation without their permission. Also, holding accurate data is vital.

Computer Misuse Act 1990:

  • Introduced to stop hacking and cyber crime

Copyright Designs and Patents Act 1988:

  • Designed to protect the creators of books, music, video and software from having their work illegally copied
  • Makes it illegal to copy or distribute commercially available software without buying the appropriate licence. When a computer is designed and implemented, licensing must be considered in terms of which software should be used
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Legislation and Privacy

Privacy issues:

  • Predicted that small computers will be embedded in everything from clothes to beermats. Consequently wherever we go and whatever we do, interfaces will end up on a database- vision of no privacy
  • Google already collects and stores data about millions of emails everyday
  • Organisations, such as the government, collect much data about individuals which is often supplied by Internet companies such as, Google
  • The US government collects, stores and monitor data about all electronic communications in the US with the intent of detecting terrorist or other illegal activity

 

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Legislation and Privacy

Using cookies:

  • Files that are sent by web servers to web browsers and which may then be sent back to the server each time the browser requests a page from the server.
  • They are used:
    • to recognise your computer when you visit the site
    • to track you as you navigate the website and enable e-commerce facilities
    • to improve website’s usability
    • to analyse use of website
    • in the administration of website
    • to personalise website for you, including targeting advertisements
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Comments

9Dreamer

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Amazing !!!!!!!!!!!!! 

N1GH7F4LL

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Great resource thanks.

purpleprankster

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Really great. Thanks OP

BigMan69.420.720NoScope

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cheers mon. this is such a sick revision resource, me and the boydem r gonna do sick in the exams now

isabellehumphries

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thankyou

isabellehumphries

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please can you make this into doubled sided A7 sized 8 per page flash cards thanks x :)

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