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|Computer System |Reliability |Disaster Recovery |Down time |

|IPOS |How reliable systems are –Unreliable systems may |Planning what to do if there is a disaster (fire, |When a computer system isn’t running, the system is |

|Anything that has a input, output device, processor |have legal impact, aircraft accidents etc., loss of |flood, natural disaster etc.). Making sure you |down. It is important to reduce the amount the |

|and storage device |data, loss of use of systems impacting on business |detect, correct and prevent problems by backups, |system is down especially when we rely on them so |

| | |spare hardware, failover, backup power |much |

|De facto |Open standards |Failover |Redundancy |

|Standards that just develop by common use. They |Standards that are publically available. |Software keeps an eye on the health of systems. If |Keeping a spare piece(s) of hardware in case one |

|become the standard way of doing things (e.g. |Open source software is publically available, |it detects a problem it may switch over to another |breaks. Making sure there is no system down time (or|

|Programmers using Comments) |experts can use and change. E.g. Android, Linux |working system (mirror system) and keeps the system |very little) |

| |No one to blame if things g wrong |running | |

|CPU |RAM |ROM |CACHE memory |

|Processors instructions |Volatile memory |Non volatile |Volatile memory located as part of the CPU chip |

|Uses a fetch - decode – execute cycle |Holds the most recent instructions that have been |Holds the boot up program used when the computer |Generally holds less data than RAM. Manufacturing |

| |processed |first starts (boot strap) |costs higher than RAM |

| |Lack of RAM is a likely cause of performance issues | | |

|VIRTUAL memory |Clock Speed |Cores |Flash Memory |

|An area on the hard disk used as memory. Used when |Speed of the processor. E.g. 4GHZ - this means the |Dual core – This means two |Solid-state memory used as low cost secondary |

|RAM is too small to deal with the amount of |CPU can process 4 billion instructions per |Processing units in the CPU |storage in portable devices and as removable memory |

|instructions. Effects the performance |cycle/second |Quad core – four processing units per CPU |For example USB, SD , Micro SD |

|LOGIC GATE - AND |LOGIC GATE - OR |LOGIC GATE - NOT |Truth Table |

|Both inputs need to be on (1) for the output to be |One or the other inputs need to be on (1) for the |The output is opposite to the input |A table that contains all of the inputs and output |

|on (1) |output to be on (1) | |combinations for a logic |

| | | |gate |

|Hardware |Software |File formats |Instructions and Data |

|All the physical parts in a computer system |Programs, apps | |When the CPU fetches data it will be treated as an |

|e.g. |Software is the programs that run on a computer. | |instruction (something it has to do) or just data |

|motherboard, keyboard, mouse etc | | |(information) |

|INPUT devices |OUTPUT devices |Secondary Storage - types |Secondary Storage |

|Hardware that allows data to be entered into a |Hardware that allows data to be output from a |Magnetic – Hard disk |Non-volatile method for storing large amounts of |

|computer system e.g. Keyboard, mouse |computer system e.g. monitor, printer |Optical – CD,DVD, BlueRay |data for long term use |

| | |Solid state – No moving parts, USB, External hard |e.g. Hard disk, USB, SD card, Micro SD |

| | |disk |Used to store progams and data, other files |

|Secondary Storage - |Secondary Storage |Secondary Storage |Secondary Storage |

|Durability |Portability |Reliability |Sizes |

|How tough the storage is, how easy it is to damage |How easy it is to move it. E.g. CD is easy to carry |Does the hardware work or does it break down easily?|Magnet hard disks – large capacity, (GB/TB) |

|e.g CD can be scratched, Hard disk more durable |around, USB is lighter. Hard disk heavy and inside |Can you reply on it? |Optical disks – (CD/DVD) holds large programs, |

| |the computer | |videos, relatively slow but inexpensive 700mb (CD) |

| | | |4,7GB(DVD) |

| | | |Flash (solid-state) – relatively inexpensive and |

| | | |good access times, can hold many GB of data |

|Binary Units |Binary to denary |Denary to binary |Binary addition (Overflow) |

| | |Place a 1 under the correct numbers that add up to |When you add numbers together and the answer won’t |

| | |make the number |fit into the number of binary digits (you need an |

| | |[pic] |extra binary digit) |

|Binary to hexadecimal |Hexadecimal to binary |Hexadecimal |Sound sampling |

|Split the binary into nibbles |[pic] |Why do we use hexadecimal numbers? Binary numbers |Storage sound |

| | |get very big and difficult to use. It is easier for |Size file - interval |

| | |programmers to convert between binary and hex than | |

| | |binary and denary | |

|Character sets |Metadata |Resolution |Colour depth |

|A standard that converts all characters on a normal |Information about the image that allows a computer |Describes the quality of an image. Measure in DPI |Refers to the number of bits used to represent the |

|keyboard into binary codes for the computer to |to recreate the image from binary |(dots per inch)/pixels |colour of each individual pixel |

|understand |e.g. the height, width, colour depth |The higher the resolution the bigger the file size |The more colours, the more bits needed so the larger|

|e.g. ASCII and UNICODE | |(and the more space you need to save it) |the file size (and the more space you need to save |

| | | |it) |

|Proprietary standards |Industry standards |UNICODE |ASCII |

|Standards owned by a company. For example |Mostly hardware standards that lots of companies |An industry-standard character set that can |A relatively simple character set that can represent|

|products/software made by Microsoft way work in a |agree to follow. For example USB |represent thousands of different characters |128 different characters |

|specific way. This will be different to Apple | | | |

|products for example | | | |

|Database – Validation |Operating system |Utility programs |Custom written software |

|The automatic checking of inputted data by a |Memory management |DO – Disk organisation tools –defragmenter |Software written specifically for you |

|computer system to ensure it is sensible, no |User interface |(reorganise hard disk and puts all of the free space|The company will get the exact software/system that |

|erroneous data is entered |Multitasking |together) |they need |

|e.g. |Peripherals |SM – System maintenance tools, system cleanup,auto |The software will work exactly how they want it to |

|Range check –1-10 |Security |updates,anti spyware |work |

|Presence check – “Required” |Windows,Android,IOS,Linux |S – Security – Firewall, antivirus |Only has features that they specifically need in |

| | | |their business. |

|Off the shelf software |Open source software |Proprietary software |Open source – things to discuss |

|Relatively cheap, (compared to custom written |Free to use |Proprietary software legally remains the property of|QLEF |

|software) |If you have skilled programmers to hand, the source |the organisation, group, or individual |[pic] |

|Easily available from most computer shops |code can be adapted to suit your particular needs |Stable product – reliable, lots of bug fixes | |

|Thoroughly tested so there won’t be any serious |(that is what 'open source' means) |Support in a timely manner – updates, help | |

|problems or bugs |May not have as much bug-fixing support and security|Usability – standard interfaces, features | |

|Lots of user support i.e. user guides, online help |patches as commercial versions | | |

|and forums | | | |

|Database |DBMS |Entities and tables |Database – Key files |

|POSD |Separation from apps and benefits |Entity - An object or thing of importance about |Foreign key - A field used in one table to represent|

|persistent, organised store of data in electronic |Custom data handling |which data is captured |the value of a primary key in a related table |

|form | | |Primary key - A field in a table which uniquely |

| | |Table - A set of data elements organised in fields |identifies each record in that table |

| | |and records | |

|Database – Forms |Database – Queries |Database – Reports |Database – Modules |

|User interface tool which allows a user to enter or |Database management tool used to retrieve |Database management tool used to present information|Database software and languages contain modules - |

|change data in a table |information based on specified criteria |to the user in a professional way |pre-written programs. |

|[pic] |SELECT * FROM PUPILS grade > C | | |

| |[Make] = "Ferrari" AND [Price] < 8000 " | | |

|Networks |Hubs/Switches |Wireless access points |Client server |

|More than one computer connected together |Hub - broadcasts data to all devices on a network. |A networking hardware device that allows a Wi-Fi |Network type where a computer is a server and others|

|Share files and devices (e.g. printers) |This can use a lot of bandwidth as it results in |compliant device to connect to a wired network (part|are peers. |

|Site (software)licences are likely to be cheaper |unnecessary data being sent - not all computers |of your Wi-Fi router) |Server - Software that provides services to a |

|than buying several standalone licences |might need to receive the data. | |client, or the hardware that is running it, |

|Users can collaborate (work together) |Switch - stores the MAC addresses of devices on a | |Client - Software or hardware that requests services|

| |network and filters data packets to see which | |from a server |

| |devices have asked for them | | |

|Peer to peer |WAN |LAN vs WAN |IP address |

|Network type in which every computer can act as a |A computer network that spans a relatively large |A local area network (LAN) is a computer network |Unique number assigned to every computer or device |

|client or server, with no central servers |geographical area. Typically, a WAN consists of two |that interconnects computers within a limited area |connected to the Internet |

| |or more local-area networks (LANs) |such as a residence, school, laboratory, or office | |

| | |building | |

|Network topology |Network topology |Network topology |Standalone |

|Bus – label the terminators, server, workstation |Ring – label the server, cable, workstation |Star – label the server, hub, cable, workstation |A computer that is not connected to a network |

|[pic] |[pic] |[pic] |All software is installed on the standalone |

| | | |computer. |

| | | |It doesn’t share peripherals with any other computer|

|Network topology |Network topology |Network topology |TCP/IP |

|Bus |Ring |Star – |TCP/IP (also known as the internet protocol suite) |

|easy to install |can transfer data quickly, even if there are a large|very reliable – if one cable or device fails then |is the set of protocols used over the internet. It |

|cheap to install, as it doesn’t require much cable |number of devices connected because the data only |all the others will continue to work |organises how data packets are communicated and |

|if the main cable fails/damaged whole network will |flows in one direction, so there won’t be any data |high performing as no data collisions can occur |makes sure packets have the correct data (so they |

|fail |collisions. |very reliable – if one cable or device fails then |can get to their destination without a problem) |

|more workstations are connected the performance of |If the main cable fails or any device is faulty then|all the others will continue to work | |

|the network will become slower because of data |the whole network will fail. |expense to install | |

|collisions | | | |

|MAC address |DNS server |Internet |Router |

|A unique number permanently assigned to every |[pic]Computer within an ISP network responsible for |A worldwide collection of computer networks |Device that forwards data packets to the appropriate|

|physical interface on a computer network (the serial|matching up host names to IP addresses |WWW - The world wide web is a collection of webpages|parts of a computer network |

|number of the network hardware) | |found on a network of computers (internet). Your web| |

| | |browser uses the internet to access the web | |

|HTML |Compression |Algorithms |Test data |

|The computer programming language hypertext markup |The process of reducing the physical size of files | |The data you use to test part of your program |

|language used for displaying web pages in a browser |Lossy – some of the quality of the original file is |A series of steps designed to solve a problem |e.g To test a maths quiz you might enter “24” or |

| |lost | |“4.2” - normal data |

| |Lossless – none of the original file quality is lost| |or “Bob” – erroneous data |

|Flow charts |High level language |Machine language |Translator |

|Diamond – Decision |Programming languages which are similar to natural |Binary instructions used by the CPU |Converts high level languages to machine code |

|Parallelogram – Input/Output |languages |[pic] |[pic] |

|Rectangle - Process | | | |

|Assembler |Compiler |Interpreter |IDE |

|Utility which converts low level code into machine |Utility which coverts high level code into low level|Utility which coverts high level code into low level|Software which provides a number of dedicated tools |

|code |code, whole blocks of code at a time |code, one line at a time |for software developers (IDLE in python) |

|Converts assembly language into machine code |Compiled program runs very quickly. |Syntax and execution errors can be quickly |Error diagnostics |

|ADD 02EA |Difficult to find errors |identified |Run time environment |

| | | |Translator |

| | | |Auto documentation |

|Variables and constants |Data types |Lists and Arrays |Errors |

|Variables |Real(float) eg 10.3, 12.5 |Array - (like a list) is a series of memory |Syntax - A type of error that occurs due to |

|A value stored in memory that can change while a |Integer eg 10,12 |locations – or ‘boxes’ – each of which holds a |incorrect spelling or grammar in a program |

|program runs |Boolean eg True/False |single item of data. All data in an array must be of|Logic - A type of error that occurs due to incorrect|

|Constants |Character eg A, space,! |the same data type |algorithm design |

|A value stored in memory that cannot change while a |String “Hello world” |List - data structures similar to arrays that allow| |

|program runs | |data of more than one data type | |

|Pseudocode |Pseudocode |Pseudocode |Pseudocode |

| |For everything within the “grade” | |[pic] |

|If 4 is less than 5 |Case based on Grade |[pic] | |

|Add 5 to 4 |    Case >=100 | | |

|Print the result |        Report “Perfect Score” | | |

|Otherwise |    Case > 89 | | |

|Print "no" |        Report “Grade = A” | | |

|Ethical |Environment |Legal |Legal |

|right and wrong as far as programmers are concerned:|Energy – energy used by computers, air conditioning,|Computer misuse act (hacking/theft) |Data protection act |

|Don’t take bribes |thinking about sustainable resource/environment |Unauthorised access to computer material |The Data Protection Act (DPA) is a law designed to |

|Don’t do tasks you cant do a good job of |friendly, reuse equipment, make things reliable |Unauthorised access with intent to commit |protect personal data stored on computers or in an |

|Avoid injuring others |Disposal of equipment – recycle at the environmental|Unauthorised modification of computer material. |organised paper filing system |

|Don’t hard the profession |centres as they can be hazardous |Making, supplying or obtaining anything which can be|Find out the 8 principles |

| | |used in computer misuse offences. | |

| | | | |

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