computer scuecven

• ALU (Arithmetic and Logic Unit)

  Completes the arithmetical and logical operations
• Control Unit


  • Controlling and coordinating the activities of the CPU
  • Managing the flow of data between the CPU and other devices
  • Accepting the next instruction
  • Decoding instructions
  • Storing the result back in memory
• Registers

  • Small memory cells that operate at very high speeds
  • Used to temporarily store data
  • All arithmetic, logical or shift operations occur in these registers
• Registers


  • Program Counter (PC)
  • Accumulator (ACC)
  • Memory Address Register (MAR)
  • Memory Data Register (MDR)
  • Current Instruction Register (CIR)
• Buses


  • Set of parallel wires which connect two or more components inside the CPU together
  • The collection of the data bus, control bus, and address bus is called the system bus
  • The width of the bus is the number of parallel wires the bus has
• Data Bus


  Bi-directional bus used for transporting data and instructions between components
• Address Bus


  Used to transmit the memory addresses specifying where data is to be sent to or retrieved from
• Control Bus


  Bi-directional bus used to transmit control signals between internal and external components
• Control signals on the Control Bus

  • Bus request
  • Bus grant
  • Memory write
  • Memory read
  • Interrupt request
  • Clock
• Assembly language


  • Uses mnemonics to represent instructions
  • Simplified way of representing machine code
  • Instruction is divided up into operand and opcode
  • Opcode is used to determine the type of instruction and what hardware to use to execute it
  • Operand is the address of where the operation is performed
• Fetch-Decode-Execute Cycle


  1. Fetch Phase: Address from PC copied to MAR, Instruction held at that address copied to MDR, Contents of PC increased by 1, Value in MDR copied to CIR

  2. Decode Phase: Contents of CIR split into operand and opcode

  3. Execute Phase: Opcode executed on operand
• Clock Speed


  • Determined by the system clock
  • All processor activities begin on a clock pulse
  • Each CPU operation starts as the clock changed from 0 to 1
  • The clock speed is the number of clock cycles completed in a second
• Number of Cores

  • A core is an independent processor that can execute its own fetch-execute cycle
  • A computer with multiple cores can complete more than one fetch-execute cycle at any given time
  • Some programs aren't optimised for the use of more than one core
• Cache Memory Types


  • Level 1 Cache: Very fast memory cell, small capacity (2-64KB)
  • Level 2 Cache: Relatively fast memory cell, medium capacity (256KB-2MB)
  • Level 3 Cache: Much larger and slower memory cell
• Pipelining


  • The process of completing the fetch, decode, and execute cycles of three separate instructions simultaneously
  • Data is held in a buffer in close proximity to the CPU until it's required
  • Aimed to reduce the amount of the CPU which is kept idle
• Von Neumann Architecture

  • Single control unit, ALU, registers and memory units
  • Shared memory and data bus used for both data and instructions
• Harvard Architecture

  • Physically separate memories for instructions and data
  • More commonly used with embedded processors
• Advantages of Von Neumann Architecture

  • Cheaper to develop since the control unit is easier to design
  • Programs can be optimised in size
• Advantages of Harvard Architecture

  • Quicker since data and instructions can be fetched in parallel
  • Both memories can be different sizes
• The purpose of the operating system is to manage hardware resources, software applications, user data, and other tasks.
• Operating systems are designed with specific goals such as providing an interface between users and computers, managing memory allocation, scheduling processes, controlling input/output operations, handling file management, implementing security measures, and supporting networking capabilities.
• Operating systems are responsible for managing input/output devices such as keyboards, mice, printers, and displays.
• Operating systems allocate and manage physical memory (RAM) and virtual memory (swap space). They also schedule processes and threads running on multiple cores or CPUs.
• They also handle file management by creating, deleting, renaming, copying, moving, and searching files on storage media like hard drives or USB sticks.
• They also handle communication between these devices and the CPU by receiving requests from them, determining their priority based on factors like urgency or importance, and allocating time slots for execution.
• Security Measures include access controls that restrict unauthorized use of sensitive information, encryption techniques used to protect confidential data, and firewalls that prevent malicious attacks from external sources.
• File management involves creating, deleting, renaming, copying, moving, searching, backing up, compressing, encrypting, and restoring files.
• File Management involves creating, deleting, renaming, copying, moving, searching, and backing up files using various commands provided by the OS.
• Security features include authentication, authorization, access control, encryption, firewalls, antivirus protection, intrusion detection, and recovery from attacks.
• Networking support includes network protocols, routing algorithms, packet switching, network configuration tools, and network monitoring utilities.
• Operating systems implement various mechanisms to ensure that only authorized users can access sensitive information and prevent unauthorized access attempts.
• Networking Capabilities allow operating systems to connect different devices over networks using protocols like TCP/IP, Ethernet, Wi-Fi, Bluetooth, etc.
• The operating system is responsible for managing hardware resources such as memory, processors, input/output devices, and network connections.
• It provides an interface for users to interact with software applications and manages user accounts, permissions, and security measures.
• User interface design principles include consistency, feedback, simplicity, flexibility, efficiency, aesthetics, and accessibility.
• The kernel is the core component of an operating system that manages hardware resources and provides basic services to user applications.
• User interfaces enable interaction between humans and computers through graphical user interfaces (GUIs), command line interfaces (CLIs), or text-based interfaces.
• The user interface is designed with the goal of making it easy for users to interact with the system and perform tasks efficiently.
• Operating systems are essential components of modern computing systems, providing services such as resource allocation, scheduling tasks, handling interruptions, and managing peripherals.
• The kernel is responsible for managing hardware resources, including CPU time, memory, disk space, network bandwidth, and input/output devices.