Computing

• Computer


  A machine that processes data
• Embedded System


  Computers built into other devices (e.g dishwasher, microwave)
• CPU


  Central Processing Unit
• Parts of CPU


  Control unit, arithmetic logic unit, cache, clock, buses
• Fetch instruction


  Control unit reads memory address of next instruction , instruction is copied from memory to a register
• Decode instruction


  The instruction that was copied from the memory is decoded (by the CU)
• Execute instruction


  The instruction is performed (by the ALU)
• Control Unit (CU)


  Controls flow of data in and out of CPU, executes program instructions
• Arithmetic Logic Unit (ALU)


  Does calculations
• Cache


  A small area of memory which can be accessed quickly by the processor and is used to store frequently or recently used data and instructions
• Clock


  Continually sends out a binary signal which is used to sync with construction (like a metronome)
• Clock speed


  The number of instructions a processor can carry out per second
• Bus


  Collections of wires used to transmit data between components of CPU and other parts of PC
• Register


  Temporarily hold data for CPU, fastest form of memory
• Volatile memory


  Temporary, requires power to retain
• Penetration testing


  When organisations employ specialists to simulate potential attacks on their network
• Malware


  Code that is designed to cause harm or gain unauthorised access to a computer system
• Non volatile memory


  Permanent memory, keeps contents even when PC has no power
• ROM contains


  BIOS (basic input output system)
• CPU Performance Factors


  Clock speed, Cores, Cache
• CPU Core


  An element of a CPU which is capable of executing one sequence of instructions at a time
• Cache type


  (L1, L2, L3) Higher level of cache can hold more but it is further away from CPU so is slower
• Tiers of storage


  Primary, secondary
• Advantages of HDDs over SSDs

  Cheaper, higher capacity, longer life
• Advantages of SSDs over HDDs

  Faster, don't need defragmenting, more shock proof, silent
• cloud storage


  A type of secondary storage where data is stored on a physical storage device in a remote location away from the rest of the system
• Pros of cloud storage

  Access from any device, can be shared easily, easy to increase storage, cheaper, provides security and backup for you
• Cons of cloud storage

  Need internet connection, speed depends on bandwidth, dependent on host for security and backups, data can be vulnerable to hacks, unclear of ownership, could be expensive in long term
• Functions of an OS (Operating System)


  Communicate with devices using drivers, provide a platform and interface for applications, control memory management, organise CPU, deal with file management, manage security
• Driver


  Translator for signals between OS and device
• Utility software


  Any software used to maintain or configure a computer
• Disk health


  Hard disks start to deteriorate over time, this utility scans the drive for problems and fixes issues where possible
• Defragmentation


  utility that rearranges files to be stored in contiguous clusters
• Compression


  It reduces the size of files so they take up less disk space
• Encryption


  Scrambles data to stop third parties from accessing it, it can be decrypted using a special key
• Backup


  A copy of a computers files and settings stored externally that can be restored in the event of a data loss
• backup utility


  Software with facilities such as scheduling of regular backups, creating rescue disks, disk images, and options for how much data to backup
• Virus scanners


  They inspect each file on your computer looking for viruses. They usually have a list of known viruses to check for - they need to be updated regularly so they don't miss anything
• System Cleanup

  Programs leave lots of temporary files on your hard drive which take up unnecessary space. These utilities go through and get rid of files like these
• LAN (Local Area Network)


  A type of computer network connecting devices owned by a person or organisation within a single location