Operating System

Operating System

1. An operating system (OS) manages all the programs on a computer. It allows software to interact with hardware and an interface between the user and hardware.

   • The layers in this structure suggest that each layer is independent of the others. You can change or update one layer without affecting the others

2. PURPOSE of an OS

   • MANAGING THE PROCESSOR: deciding which process to execute next and manage instructions currently being executed.
   • MEMORY MANAGEMENT: allocating and managing memory by paging and segmentation. It also manages virtual memory
   • PERIPHERAL DEVICES: using device drivers to translate instructions that can be understood by specific models of hardware. E.g printers
   • PLATFORM FOR SOFTWARE AND UTILITY: allows the users to interact with the OS to manage files and a range of utilities, for example defragmentation
   • USER INTERFACE: allows users to interact with programs, through command line or GUI.

3. TYPES of OS

   • DISTRIBUTED: one instruction is being carried out in one location whilst another instruction is being carried out in another location. It is all coordinated to the system
   • EMBEDDED: software that is designed for a specific purpose-like software for a washing machine. This software is dedicated to the hardware and is very memory effcient.
   • MULTITASKING: the CPU can only do one thing at a time. Time is allocated to different processes.The computer will decide which instruction will require more time
   • MULTI USER: only one user can use the computer at any one time. However, several users can have login on one computer.
   • REAL TIME OS: Where the system is guanteed to respond within a specified period of time. This has lots of spare capacity-redundancy. e.g airbag in car will detect the collision within 1 millisecond but will fire the airbag within 10s.

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