Hardware and Communication*

• Classic von Neumann architecture uses only a single processor.
• The most common type of multi-core system is called the parallel processor.
• In parallel processing, a task is split in smaller sub-tasks or "threads" and executed simultaneously by multiple cores and then brought together with a sequential execution.
• In a multi-core system, all processors need to communicate continuously to ensure if one processor changes a key piece of data, the other processors are aware and can adapt if necessary.
• The advantages of a multi-core system are that more instructions can be processed in a shorter time and tasks can be shared to reduce the load on individual processors and avoid bottlenecks.
• The disadvantages of a multi-core system are that it is difficult to implement, results from different processors need to be combined at the end of the processing meaning it can be complex and adds time to execute; not all tasks can be split across multiple processors and concurrency introduces new classes of software bugs.
• Runtime calculations are used to calculate the minimum runtime of executing a program on a certain number of threads. Amdahl's law is used to calculate it but irrelevant for the WJEC.
• Assembly Language Typical Commands

  
• Optical Character Recognition (OCR) converts printed media into editable text documents using a scanner. It is a post-processing step that occurs after a document has been scanned. It performs pattern matching by scanning the images for shapes it can recognise as letters, numbers or symbols. This is done by comparing the binary data to an internal database of known character shapes.
• Optical Mark Recognition (OMR) scans through multiple choice boxes and inputs the box that has ink on it. If all boxes have ink on it then the first box will only be used.
• Magnetic Ink Character Recognition (MICR) scans for iron oxide ink and use that to read for data.
• Resistive Touch Screen are made up of two thin transparent sheets and when the sheets touch each other, a voltage is recorded at that position. A certain amount of pressure is needed to make the sheets touch and will be used to input data.
• Capacitive Touch Screens use the human body to conduct electricity when touching the screen. At that position, data is inputted respectively.
• Voice input can be used to issue spoken commands to a computer system via a microphone. The computer will read the analogue soundwaves and convert it into digital data.
• Vocabulary dictation can be used to input data into a computer system. This done by the user speaking into a microphone and the computer will try to change the spoken words into typed text.
• Voiceprint recognition is the process of capturing a person's voiceprint then digitising and storing this data on a computer system.
• Just learn it:

  
• Flash Storage Devices (SSD) use flash memory to store data and utilise EEPROM (you should know by now).
• Optical drives work by using lasers to store data by burning microscopic indentations into a disc. This pattern of indentations is created in a spiral pattern, starting from the middle. Indentations and their absence create pits and lands which are used to store binary data. The laser is aimed at the disc and reflected back which can interference with the original laser - affecting it being a pit or a land.
• Network-attached storage devices can be used to bring multiple drives together to act as a single drive. But very expensive.
• Redundant Array of Independent Discs is used to bring multiple drives to act as a single drive.
• RAID 0 Striped - provides improved performance and additional storage but does not provide any fault tolerance.
• Raid 1 Mirrored - each disc provides the same information which provides some fault tolerance. Read speed is increased.
• Raid 3-6 Striped Parity - Requires at least 3 discs in the array. It provides fault tolerance, parity checks and error connection. The parity information is stored on a single drive so the other drives can continue working when one of the drives fail.
• Fragmentation means all the data in a file is split apart and stored on different paths of the disc.
• Defragmentation is the process where files are physically re-arranged on disc so that they are no longer fragmented and the parts of each file are stored together.
• Handshaking is the process of two computers agreeing to use a set of protocols for communication. The handshaking signal is sent between computers before data is transferred.
• A Network Interface Card (NIC) is a wired piece of hardware used to connect a PC to a network.
• A Wireless Interface Card (WIC) is a wireless piece of hardware used to connect a PC to a network.
• A hub allows more than computer to be interconnected in a network by connecting them into one central device.
• A switch manages the routing of packets from one port to another.
• A router is used to connect LAN to WAN.