7.2 System. Sub-system and Structured Diagram

• Computer system


  Made up of software, data, hardware, communications, and people
• Computer system


  • Each computer system can be divided into a set of sub-systems
  • Each sub-system can be further divided into sub-systems and so on until each sub-system just performs a single action
• Example in Computer


  • Login page to the device
  • Alarm Clock
• Example in Instagram


  • Main sub-systems = Posts, Story, Reels
  • Small sub-systems = User Interface, Login page, Server
• Problem decomposition


  Understand how a problem can be decomposed into its component parts including inputs, processes, outputs, storage
• Components of a computer system

  • Inputs
  • Outputs
  • Processes
  • Storage
• Design and construct a solution

  Use different methods including structure diagrams, flowcharts, pseudocode
• Structured Diagram


  • Show top-down design in a diagrammatic form
  • Hierarchical, showing how a solution can be divided into sub-systems with each level giving a more detailed breakdown
• Top-down design


  Decomposition of a computer system into a set of sub-systems, then breaking each sub-system down into a set of smaller sub-systems, until each sub-system just performs a single action
• Algorithm


  A set of instructions that are designed to perform a specific task, usually by taking inputs, running them through steps, and producing outputs
• Flowchart, Pseudocode


  Used to start developing a sub-system using an appropriate programming language