Computer systems and data bases

• Hardware


  Physical components of a computer such as the CPU.
• Software


  Programs within a computer system e.g application software
• System software is software that assists with the running or management of a computer system. Application software is any software added to the system that enables a user to perform a task. e.g can be used for web browsers, games and database software.
• Embedded systems are computers built into other devices. They are usually dedicated systems. They are often used as control systems - they monitor and control machinery in order to achieve a desired result. As they are dedicated to a singular task, they are cheaper to produce and more efficient at performing a task than a general purpose computer
• CPU stands for Central Processing Unit. It processes all data and instructions that allow a system to function. CPU architecture describes the main components and how they interact with each other and with components outside the CPU. The CPU has 5 main parts; the control unit, the arithmetic logic unit, cache, the clock and buses.
• Buses


  Buses

  • Are a collection of wires used to transmit data between components
  • high speed internal connections
  • manages/regulates the flow of data around the CPU and to main memory.
• The Control Unit (CU)


  the CU

  • Controls and coordinates activities of the CPU
  • Directs flow of data between CPU and components within and outside the CPU
  • Manages the FDE cycle of program instructions
• Arithmetic Logic Unit (ALU)


  The ALU

  • Performs arithmetic and logic operations on data
  • gateway between primary memory and secondary storage
  • Manages arithmetic operations, it does not store or control anything
• The Clock


  The clock

  • Regulates the number of fetch-execute cycles carried out per second
  • sends out electrical impulse at a constant rate between 1 and 0, used to synchronise when instructions will be carried out
  • The number of clock cycles per second is called the clock speed, measured in hz
• Registers


  Registers

  • Are small amounts of high speed memory contained within the CPU
  • Used by the processor to store small amounts of data that are needed during processing
  • Very quick form of memory that are quick to read/write to
• Cache


  Cache

  • small amounts of high speed Random Access Memory (RAM)
  • Slower than registers, but faster than RAM
  • Stores regularly used data so the CPU can access it quickly
  • Temporarily stores data
• Processor perfomance is the speed at which the processor can carry out instructions. It can be affected by clock speed, cache size and the number of cores the processor has. A processing unit within the CPU is called a core. the more cores a CPU has, the greater number of instructions it can process in a given amount of time.
• An operating system is a collection of programs that manages and controls the computer. An operating system…

  • Manages system security and user accounts
  • Manages file and disk management
  • Organising the CPU and its processing tasks
  • Communicates with input and output devices via device drivers
  • Provides a platform for applications to run on and an user interface
  • Controls memory management and allocation
• Input/output devices


  I/O devices…

  • Are hardware devices connected to a computer, such as a screen, printer or keyboard
  • Operating systems use device drivers to communicate with I/O devices connected to computer system
• Device drivers contain instructions on how to operate/control a device

  • They act as translators for the signals between the OS and device.
  • Any device can be used with the operating system, as long as a device driver is available for it
  • Device drivers can be updated, for better performance and to remove bugs
• Application Management 


  The OS provides a platform for applications to run and manage system resources to allow computers to run multiple applications at once - known as multi-tasking. Application programs and hardware communicate through an interface provided by the OS. This is known as the Application Programs Interface (API). It also allows applicators to access hardware and other I/O devices as needed, including RAM and secondary storage.
• Processor Management/CPU management


  When an application is launched, it creates one or more processes. CPUs can only carry out instructions one at a time. Each process is allocated a priority by the OS. In order to perform multi-tasking, the CPU swaps between tasks/processes very rapidly.
• File and disk management

  The OS is responsible for file management, e.g the movement, editing and deletion of data. It also manages the hard disk by splitting the physical disk into sectors and decides which sectors to write data and keeps track of free space on the disk.
• Security management 


  It allows individual users to be created and deleted. Access levels can be given to users, such as administration rights or standard user rights. It also keeps a log of files a user creates, accesses and deletes.
• Read Only Memory (ROM)


  Permanent, non-volatile type of memory. It generally can’t be changed after its created, only accessed. It stores important data that won’t get affected by a loss of power. Data can be read, not written to.
• The FDE cycle


  Stands for the fetch decode execute cycle. It is used by the CPU to run instructions. Each cycle retrieves an instruction from memory (fetch), translates it into a series of commands (decode) and then performs the required action (execute)
• There are 4 types of memory:

  • Registers
  • Random Access Memory (RAM)
  • Read Only Memory (ROM)
  • Cache