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AS and A Level: Computer Science

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  1. Signal Theory

    Hubs operate on the physical layer of the OSI model and they are protocol transparent. This means that they do have the ability to set upper layer protocols such as IP, IPX or a MAC addresses. Hubs just extend them do not control the broadcast or collision domains. Bridges - Used to increase the performance of a network by dividing it into separate collision domains. Even though they are more intelligent than hubs due to the fact that they operate at the Data Link layer of the OSI model, they still are not able to control the upper layer protocols.

    • Word count: 6197
  2. LAN & WAN Protocols

    Ethernet - Commonly used cable when creating LAN networks. It is also the common standard when creating LAN networks. IEEE 802.11 - This is the set protocol used for WLAN. The IEEE stands for Institute for Electrical & Electronic Engineers. You could also have IEEE 802.12 which is completely a different standard used for WiMAX. Token Ring - A computer sending data needs to hold a token, when all the computers are sending the data then it does not need to hold the token. Layer 3 (Network) - Responsible for end to end packet delivery.

    • Word count: 2387
  3. Strategy and Change

    Reporting the Surprises A current and comprehensive perspective of the marketplace has become a strategic necessity, but the means for gaining and maintaining such a perspective challenges old management models. The decentralized, self-organizing social communication structures required to efficiently gather and circulate the knowledge that individuals learn and develop don't fit gracefully under the hierarchical, centrally controlled structures that still rule most organizations. Most organizations are looking for ways to make their wholes smarter. They are changing their information strategies to keep up with the velocity of the Net and to keep up with, or preferably overtake, their competitors.

    • Word count: 1245
  4. Threats to customer Data

    A true virus can only spread from one computer to another when its host (some form of code) is taken to the target computer, for instance because a user sent it over a network or the Internet, or can increase their chances of spreading to other computers by infecting files on a network file system or a file system that is accessed by another computer. Viruses are sometimes confused with computer worms and Trojan horses which are like viruses but are technically different, in effect creating a damageable system to allow access to the user's computer. A worm can spread itself to other computers without needing to be transferred from someone, Worms and Trojans, like viruses, can cause harm to a computer system, functional performance, or networking throughput, when they are made.

    • Word count: 854
  5. Betting Shop computer investigation

    ACPO state there are 4 principles that should be adhered to at all times, so when reading this must be took into consideration. The four principles are as follows:- Principle 1: No action taken by law enforcement agencies or their agents should change data held on a computer or storage media which may subsequently be relied upon in court. Principle 2: In exceptional circumstances, where a person finds it necessary to access original data held on a computer or on storage media, that person must be competent to do so and be able to give evidence explaining the relevance and the implications of their actions.

    • Word count: 2277
  6. AQA Computing CPT3 June 08 Peter's Petrol Pumps

    customers that have used the pump in the day 11 - Password String Stores the password required to unlock the console password123 Presence USER INTERFACE MAIN FORM This form will be shown first when the program is run. It will be split in 2, with the pump on 1 side and the console on the other side. For security reasons, the console will not be shown without a password being entered to unlock it. Most of the functions will be carried out from this form, such as filling the car with petrol and Peter using the console functions.

    • Word count: 2151
  7. Social Issue Essay

    Iran claims that its research into this field of science is so that the country can produce nuclear energy that will provide electricity to its country. And while many western countries and observers look on with concerns about the issue - and more importantly, Iran's potential danger to the world with nuclear weapons - I do not believe that the scientists in both Iran or elsewhere in the world should be held responsible for the potential consequences of their ground-breaking advances.

    • Word count: 1216
  8. Evaluation of a computerised system

    * Data must be backed up to minimise loss of data and to reduce the amount of work if data does get lost A sufficient back-up plan has been constructed which included at least two ways of backing up records at regular intervals. * To find information about an item quickly The 'Find product' query is a good way of finding information about an item quickly. It allows the user to search for an item using its name or in a separate query a product ID can be used.

    • Word count: 2333
  9. Analysis of Johnson Music

    Initial ideas about the problem In my experience, the way the shop handles sales of products is very inefficient. One major problem is the way the shop handles stock control. All of the shop's stock control is paper-based, meaning every time a product is sold at the shop, paperwork has to be filled in to keep control of the stock. A customer can go to the counter and say they want to purchase a guitar, or any other Ibanez products.

    • Word count: 9304
  10. WANs in Organisations

    METROPOLITAN AREA NETWORKS This is a network that covers between 2km and 5km and is often found in metropolitan cities. These networks are usually owned by a single company but are provided for use by everybody. Occasionally a network such as this will be implemented by a public company such as the local council. Generally speaking, a MAN is any type of network that connects computers together in an area of around 2km - 5km. CAMPUS NETWORKS A Campus network is a network of less than 2km that is operated by a single entity.

    • Word count: 830
  11. WAN Protocols

    It is only when manufacturers stray away from these set protocols that compatibility problems will occur. Figure 1 The Protocols and their Relationship with the TCP/IP Model The OSI Model The TCP/IP Protocol suite does not directly map to the OSI model as TCP/IP relies on four layers and the OSI model uses 7. The top three layers of the OSI model map straight to the Application, Presentation and the Session layers of the TCP/IP Suite. Most of the protocols mentioned on this information sheet are found at the application layer of the OSI model; FTP, HTTP, SNMP, Telnet are all found here.

    • Word count: 1402
  12. WAN Devices

    Hub's only use bits to send the data and cannot understand anything above bits on the OSI model. Bridges Bridges and Routers are quite similar - they both direct traffic between two devices. A bridge will connect hardware together using hardware assigned MAC addresses. Bridges are a layer two device. This means that bridges cannot determine the type of network that they're running on. Routers Routers, like hubs and switches, connect together multiple networks. Routers use headers and forwarding tables to create and send packets to determine the path through the networks and this means they operate at level 3, the network layer.

    • Word count: 1079
  13. Network Planning

    Peripherals used should be wireless so that there are no unnecessary wires when the mouse and keyboard can be stored away. Each till needs specialist till equipment - software, scanner, till drawer, price display, and keyboard and receipt printer. There is also a need for lasers printers as the current dot matrix printers are slow and provide bad quality print outs. Bargain Booze has also requested enhanced security to include CCTV running separately from the till systems, preferably handled externally.

    • Word count: 1485
  14. Subnetting and IPs IP addresses are an extremely important part of sending and receiving data across the Internet or across multiple networks. The IP address is the address assigned to each device and computer.

    only 126 Class A networks can exist across the entire Internet. However, each of these networks can have 16 million hosts. Because of the rarity of these addresses, only 40 companies across the world actually have these addresses and they are all extremely big companies (examples include General Electric Company, IBM, and Apple as well as a few social security companies) and the rest are reserved used by the companies that manage IPs in various geographical regions. Class B addresses are almost split down the middle - theoretically half of the digits are for the network ID and the other 8 are for hosts.

    • Word count: 2124
  15. Processor Scheduling

    However, there are two errors that may occur. Firstly, the job when dispatched may conflict with other processes in which case will be entered into the waiting queue. From the waiting queue it will enter the cycle again. Secondly, the process may timeout, also known as a timer interrupt and from here have to repeat through the cycle again. Types of Processing Methods There are four different methods of processing. They are First Come First Served, Shortest Job First, Shortest Remaining Time First and Round Robin. They all have their differing properties and they shall be explained briefly below.

    • Word count: 1114
  16. Input Output Functions of an Operating System

    3. Polled vs. interrupt driven - Modern operating systems use interrupt driven methods in preference to its counterpart. There are numerous reasons for this; however the most considerable would be the error detection efficiency. Although the polled had this function, its efficiency at dealing with it, then clearing it from the system was very poor indeed. Polled works with 3 differing modes and they are status, data and command. Processing Techniques There are 3 different techniques used by the processor for input output subsystem they are as follows; Polled mode/programmed input output - This method is poor; it stops the CPU when it determines whether to read or write.

    • Word count: 954
  17. Open and Closed Loop Control System

    The answer to this is that is doesn't. Open-loop control is useful for well-defined systems where the relationship between input and the resultant state can be modeled by a mathematical formula. For example determining the voltage to be fed to an electric motor that drives a constant load, in order to achieve a desired speed would be a good application of open-loop control. If the load were not predictable, on the other hand, the motor's speed might vary as a function of the load as well as of the voltage, and an open-loop controller would therefore not be sufficient to ensure repeatable control of the velocity.

    • Word count: 1092
  18. What is E-Commerce?

    It's far more global than this, if someone was to mention e-commerce instantly now we think of E-Bay. E-Bay has a huge number of users, some 250,000,000+ and this will be a constantly growing figure. It's the same with bank transactions, this can all be done online and this is a form of e-commerce also. But why has this become such a huge part of the modern day life, when 10 years ago it was almost unheard of? The reason for this is the demand to make our lives easier. Making the most of our time provides the efficiency needed to maximise returns in other areas.

    • Word count: 2069
  19. Free essay

    What is Visual Programming

    JTree * JTable * JToolbar * JInternalframe * JProgressbar * JList * JTextfield * JTextarea * JPannel * JTabbedpane * JScrollBar * JScrollpane * JMenubar * JPopupmenu * JSlider * JLayeredpane * JDesktoppane * JOptionpane * Jcolourchooser * JFilechooser * JFrame * JDialog Java AWT * Label * TextField * Checkbox * List * Scrollbar * Panel * ScrollPane * Canvas * PopupMenu * Button * Textarea * Choice * MenuBar VB.NET C# * Pointers * Buttons * Ceckbox * Checklistbox * Combobox * DateTimePicker * Label * LinkLabel * ListBox * ListView * MaskedTextBox * MonthCalender * NotifyIcon *

    • Word count: 942
  20. Free essay

    Hardware and Functions of a Micro Processor

    Below is an example of the structure of a microprocessor. The CPU has four main functions, fetch, decode, execute and write back, these processes will be outlined in greater depth in the latter part of this assignment. Let's now have a look at some of the microprocessors components. Logic Gates Logic gates aid the computer in receiving results dictated by a set of components and rules. The logic gate has several inputs but only one output dependant on the various inputs.

    • Word count: 2170
  21. Security Issues of E-Commerce

    With this in mind the businesses have to be a lot more careful. So how are these precautions taken? Below is a list of the most common issues that both consumer and businesses may face. Below that is an explanation (only briefly) of what the actual implications mean. * Disruption or denial of service attacks * Defacing web sites * Unauthorized use of credit cards * Invasion of privacy-especially related to minors * Unauthorized changes to database records * Fraud * Spreading viruses * Employee misuse of the Net * Employee privacy * Email harassment Disruption or denial of service attacks A denial-of-service attack (DoS attack)

    • Word count: 3103
  22. Free essay

    File Management - Operating Systems

    When a user creates a file it is stored on the hard drive, or removable media. This is given a human name, for example ricki.doc. From here the programme is run by the operating system searching for a particular attribute. How does it do this? Well, it needs a SFID. An SFID is system file identification. Every file or folder is given one of these when created on the system. This allows the operating system to associate every file that's created with a number accordingly.

    • Word count: 912
  23. Free essay

    Incentives and Barriers to E-commerce

    All of the above are time consuming tasks and are going to cost the business. Is it really worth undertaking all of these processes if the revenue to be made is minimal? These are all questions that need to be considered. As far as the consumer is concerned we have a completely different type of situation. The consumer is to be possibly sat at their home and can only get a small picture of the item they want to buy, also, if it is clothing that they are to buy then the size of the item may not be exactly to their liking.

    • Word count: 5845
  24. Different Control Sensors

    floor as soon as the pressure switch is activated the door will open, this form of switch will tend to require a form of displacement. Another example if where a pressure switch/monitor may be found is within a car. When the tyres reach a certain pressure the control system kicks in and then they are warned to pump them up. If we consider large industries such as factories with combustion engines then we need to bear in mind that there needs to be some form of indication when present conditions change within the mechanism, this is also where a pressure sensor will come in handy.

    • Word count: 1564
  25. Basic Database Building

    The database normalisation was done to second form and this left me with the following tables. Here we can see the differing tables that I have adopted; the tables contain all the necessary information to carry out the tasks needed in the bullet point list at the top of this document. However, the programme could be expanded upon greatly but at the current moment this wasn't needed. Database Relationships The database relationships were the trickiest bit, with the need for accurate lining playing an important part. The linking of the database was minimal but appropriate and this is what helped me in creating a working database, below is the screenshot of the relationships.

    • Word count: 2594

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