Operating Systems

Multitasking
1. Run more than one process at a time
  1. CPU turns attention to another process instead of standing idle
    1. Schedules processes
  2. Switches between programs very quickly
    1. Not noticeable to user
  3. If a program is terminated it's because it's allocated time has run out or it is an external or interrupted event
2. Multitasking
The User Interface
1. Provides means of communication between the user and the operating system
  1. The Command Line
    1. The place where commands can be given to the Operating system
    2. Issue single, powerful commands in order to manage the system
    3. Can be collected into batch files or shell scripts
      1. So single commands can use multiple actions
  2. User Interface
2. Graphical User Interface
  1. Most Personal Computers and devices will use a GUI
    1. Small Icons
      1. Reduce need to learn commands.
      2. Particularly suited to touchscreen
      3. Limits amount of customisation of actions
    2. Voice Input
      1. Typically require: yes/no or numerical responses
        Increasingly capable of dealing with more complex ones
Memory Management
1. Manage available memory
  1. Primary memory holds programs and data currently in use
    1. Makes sure they are stored safely and efficiently
2. Memory Management
Drivers
1. Required for each peripheral
  1. Application needs to pass on a request to the driver which will translate it into codes for that specific device
    1. Not only specific to device but to the operating system aswell
      1. Drivers
2. "Bootstrapping"
  1. Starting small and loading programs one at a time while each program is connected to the next program to be executed in the sequence
3. Software sends out system call
Peripheral Management
1. Peripheral devices are essential for a computer system to input, output, and store data.
  1. Devices need to communicate with the computer sysytem
    1. (See Drivers)
2. Peripheral Management
File Management
1. File management is finding where files are stored
  1. E.g. hard disk drive/solid state drive
  2. Needs to know specific track, sector, and surface
    1. User doesn't
      1. ...but the Operating System does
        File management
Kernel
1. Deals with low level hardware operations
  1. Any application must interface with the Kernel to operate hardware
    1. Helps minimise the risk of the application causing problems with the hardware and basic memory operations
    2. Stops applications from issuing commands directly
2. Kernel can provide a range of user interfaces
3. Kernel
Firmware
1. Operating Systems used on home computers/large systems are typically loaded from a disk.
  1. In smaller devices, there is no requirement for a disk and Operating System is permanently stored in ROM or flash memory chips
    1. This is Firmwire
      1. Consists of small programs
2. Firmware
Multi-User
1. Many users may use the same system simultaniously
  1. Operating System responsible for allocating memory, storage, and CPU time to multiple users
2. Multi-user
Real Time
1. Safety-Critical Systems require very short and guaranteed response times
  1. Generally fixed at a small fraction of a second
    1. Instant response
2. Real Time

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Operating Systems

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