Software

• System Software


  Provides the services that the computer requires, including operating system and utility software
• Application Software


  Designed to carry out a specific task the user would need for completing a variety of tasks
• Systems software is made up of two core elements: the operating system and utility software
• Operating System


  A program designed to run other programs on a computer, managing both software and hardware resources
• Examples of Operating Systems

  • Windows
  • MAC
• Resources


  Anything that a program requires for its execution
• Utility Software


  Performs specific tasks related to computer functions, resources, files and security
• Examples of Utility Software

  • Security utilities (Anti-Virus, Encryption, Firewall)
  • Disk organisation utilities (System Clean-Up Tools, Disk Defragmentation Tools)
  • Data compression utilities
  • File backup utilities
• Freeware


  User is not allowed to access the source code, cannot tailor the software to their needs or fix any bugs, still covered by copyright
• Free Software


  User can access the source code, can tailor the software to their needs and fix any bugs, can redistribute the software under the same terms as the original
• Shareware


  Gives a trial version of the software for a limited time with limited features free of charge, requires the user to pay a fee if the full version is needed, protected by copyright
• Ethical considerations when distributing software

  • Accessibility of software
  • Age appropriation
  • Copyright
  • Distribution of malware
  • Environmental impact of distribution media
  • Following guidelines of professional bodies
  • Intellectual property theft
  • Offensive materials
  • Plagiarism
  • Privacy of data
  • Security of software
• Diagnostics


  The process of checking the status of a device to find out if it has a problem or needs to communicate
• Operating System


  • Managing Files (creation, deletion, permissions, organisation)
  • Handling Interrupts (software errors, user actions)
  • Managing Memory (RAM allocation, multitasking)
  • Providing a Platform for Running Applications
  • Providing System Security
• Hardware


  Physical components of a computer system
• Firmware


  Software embedded in hardware, provides low-level control
• Operating System


  Software that manages hardware and software resources
• Application Software


  Software that performs specific tasks for the user
• Software-Hardware interaction


  1. Application software talks to operating system

  2. Operating system talks to hardware

  3. Hardware processes and sends information to operating system

  4. Operating system sends information back to application software
• Firmware (Bootloader/BIOS)


  Software that provides initial boot-up instructions and low-level hardware control
• Computer boot-up process


  1. Firmware (BIOS) explores ROM for initial boot-up instructions

  2. Firmware (BIOS) sends instructions to RAM to be processed by operating system
• Firmware (BIOS)


  • Provides low-level control for hardware devices
  • Ensures hardware devices are available for communication with operating system
• Interrupts


  Signals that cause the CPU to temporarily stop executing its current program to handle a higher priority task
• Types of interrupts


  • Hardware interrupt (caused by hardware device)
  • Software interrupt (caused by application request or error)
• CPU registers


  • Program Counter (location of next instruction)
  • Current Instruction Register (holds current instruction)
  • Memory Address Register (location of data in RAM)
  • Memory Data Register (data from/to RAM)
• Interrupt handling process


  1. Interrupt service routine added to specific area

  2. Current register values pushed onto stack

  3. Interrupt instructions fetched, decoded and executed

  4. Original register values popped from stack