Paper 1

Paper 1

1. CPU

   • The fetch-decode-execute cycle
     •    An instruction is fetched from memory. The instruction is then decoded. The decoded instruction is then executed so that the CPU performs continuously. The process is repeated. The program counter is incremented. The instruction is transferred to the MDR. The address of the instruction to be fetched is placed in the MAR.   
   • Virtual memory
     • virtual memory is an extension of RAM onto the secondary storage, this is slower than having more RAM however it is cheaper. this extension of RAM allows for more important pieces of data to be kept where the CPU can access it quickly and still allows other pieces to be kept relatively quicker than being in secondary storage.
   • Factors affecting performance
     • Number of cores, size of cache, clock speed, bit amount, address bus width, data bus width
   • Control unit
     • sets the timing signals for the CPU, controls the actions of the CPU, interprets input and output devices
   • Arithmetic logic unit
     • calculates arithmetic and logic calculations then outputs the result
   • Cache
     • volatile, extremely fast memory used by the CPU to quickly access data and instructions.

2. Secondary Storage

   • Characteristics
     • Capacity/size Speed Portability Durability Reliability Cost   
   • Benefits of storing data on an optical storage device
     • Cheaper than USB sticks Easily transported in the post as they are flat. Long potential life span. Quick to access data.

3. Networking

   • Benefits of using a network
     • sharing files- multiple use at the same time sharing peripherals- fewer needed, saves money share internet connection each LAN device has access to same internet- centralised updates, update all at once centralised accounts- access account on all devices centralised backups- all devices backed up automatically improved communication- cheap and via email
   • Benefits/drawbacks of peer-to-peer vs client-server network
   • Advantages of a mesh network
     •    No single point where the network can fail. If the central server or switch in a star network fails the whole network goes down. If one device fails in a mesh, data is sent along a different route. Expensive to set up due to wiring but can reduce cost by using wireless technologies.   
   • Advantages of a star network
     •    It is easy to add a new node or device. Management of the network can be done centrally. Fewer data collisions can occur. If a node or device fails it does not affect the rest of the network. A signal does not need to be transmitted to all computers in the network.   
   • How packet switching works
     •    The sending device splits the data into packets. Each packet is given a packet number. The router uses header to decide which route to send the packet. The route chosen depends on traffic. Packets may not follow the same route. Packets may arrive out of sequence. Receiver uses header and packet number to re-assemble data. If a packet has not been received will send out a timeout message. If data/checksum matches receipt confirmation is sent.   
   • Benefits of using virtual networks
     •    Increased security as users need to log onto the virtual network. Users can only see the data/files/people related to them. No access to other data/files/people they should not have access to. No need to set up separate individual physical networks.   
   • factors that can affect network performance
     • bandwidth, cabling, 
   • Factors that can affect Wi-Fi performance
     • barriers, bandwidth, distance from access point
   • The 4 layer model
     • Application layer Transport layer Network layer Data Link Layer
   • Advantages of using layers in networks
     •    Networks are complicated and working in layers helps to simplify the problem. Each layer is self-contained and does not need to know how the other layers work. It allows different developers to concentrate on one aspect of the network. A layer can be taken out and edited without affecting other layers. Products from different manufacturers will work together.   
   • IP addresses vs URLS
     •    URL needs converting (using DNS) to IP before it can be accessed. does not require conversion. URL includes the protocol and location (and resource name) IP specifies the address only. URL is much easier for humans to remember than IP addresses.   

4. Systems Software

   • How defragmentation works
     • files/data on the hard disk drive are moved empty spaces collected together related files/data are moved to be stored together fewer disk accesses are needed
   • Advantages of proprietary software
     • very secure, customer service, well developed, small likelihood of bugs
   • Advantages of open source software
     • wide support from many developers, customisable, many different versions
   • Benefits of memory management by the OS
     • it allows for multiple programs to be open and running at once without using the same memory and clashing
   • How hard disks become fragmented
     • disks become fragmented when files are saved then deleted, once deleted they leave a space. this space isn't filled in by the other files moving up to fill it, it stays there till a new file is saved in it, if the new file is too big it's separated to fill the gap.
   • Backups
     • full
       •    A copy of every file is taken each time the backup is run. Uses a lot of storage space. Can take a very long time to back up all the files. Faster to restore as it is only necessary to restore from one backup.   
     • incremental
       •    A full backup is taken the first time and then only the files that have been created or edited since the last backup are copied. Uses less storage space than full backup. Much quicker to backup files as fewer files need to be copied. Slower to restore as it is necessary to restore from multiple separate backups   

5. Laws

   • the laws
   • principles of the data protection act

6. cloud storage

   • advantages
     •    It would offer additional storage. It is a very efficient method of backing up data. It would allow their employees to work from anywhere. It is environmentally friendly. Easy to increase availability of storage. You don’t need specialist network skills. The third party provides security so no need to purchase software/hardware. The third party provides backup so no need to purchase software/hardware. Cheaper as doesn't need its own infrastructure.   
   • disadvantages
     •    You need a constant internet connection. Reliant on third party to carry out security procedures but you may still be liable if things go wrong. Reliant on third party for back up connection. Data stored in the cloud will be vulnerable to hacking and other threats. Issues regarding data ownership. Implications of Data Protection Act.