IB Computer Science/Science Systems Life Cycle and Software Development/Systems Design
System Design
[edit | edit source]Parts Of A System
[edit | edit source]The main parts of any computer system follow the input-process-output model of data flow:
However, hardware also needs backing storage, as there is no permanent storage in the CPU:
Layers of software have also been implemented, so no direct contact with hardware is necessary:
Data in a System
[edit | edit source]When data is in a system it is often shown in flow diagrams with the following symbols:
Data Capture and Output Presentation
[edit | edit source]- Data Capture
- Manual Data Entry - Keyboard, mouse (Example: adding client records to a database)
- Direct Data Entry - OCR/OMR scanners, barcode scanner etc (Example: Lending a book or locating borrower details)
- Automatic Data Entry - Sensors (Example: automatic temperature control)
- Data Presentation
- Temporary Displays - VDU, LCD Display (Example: showing a price on a display)
- Permanent Display - Printer (Example: a receipt)
- Electrical/Mechanical Output - Actuator (Example: Sending credit card data from a bank to a cash machine)
Design Data Structures
[edit | edit source]Hardware Components
[edit | edit source]Suitable Interface
[edit | edit source]The major two user interfaces are command line interfaces (CLI) and graphical user interfaces (GUI).
CLI's are much easier to implement and use less memory, however there is a much greater learning curve, yet long-term users may find them quicker than other interfaces.
GUI's are much more complex to implement and use more memory, they also require a mouse. Yet, icons make it easier to remember commands and these are grouped in menus. There is a much smaller learning curve. GUI's can also be referred to as 'WIMP' (Windows, Icons, Menus, Pointers)
System Flowchart
[edit | edit source]Usually X-shaped with inputs at the top of the X, processing in the middle and outputs at the bottom. Some of the shapes are parallelogram for input/output, trapezium for manual input, square for process, rectangle with curved bottom for document, and cylinder for disk storage.