Operating Systems

Operating Systems

1. An operating system is software that manages the computer. (Hardware, software, security and UI)

2. Purpose of Operating Systems

   • Managing the processor
     • Deciding which process to execute next and handling interrupts to the currently executing process
   • Managing the memory
     • Allocating and managing the memory used and relinquished by processes using paging and segmentation. Managing VM
   • Managing external devices
     • Using device drivers to translate operating system instructions into those understood by specific models of hardware device, e.g. printers
   • Provides a platform for software and utility programs
     • Provides a framework for applications to run, allowinf them to open and close files easily for example. The user can also interact with the operating system to manage files and use a range of utilities, e.g file explorer and defrag
   • Providing networking
     • Communication through protocols to other machines and devices
   • Managing security
     • Servicing and denying requests to access the resources connected to the computer, e.g. shared devices
   • Providing a UI
     • Users interact with applications through the interface provided by the OS. This may be grphical, menu driven or command line

3. Types of OS

   • Distributed
     • You can combine the processing power of multiple computers across a network for a single task
     • In distributed computing, the OS controls and coordinates the computers, presenting them to the user as if they are a single system
   • Multi-user
     • Most OS such as in schools allow > 1 person to use a computer at the same time
     • The computer will manage the user's various permissions and access rights when they log on
     • Server OSS will handle the requests of multiple people using different computers on a network at the same time
   • Multi-tasking
     • We expect to have >1 application open at once
     • In single-processor systems, each active program is scheduled to receive a tiny time slice in quick rotation, giving the impression they are operating at the same time
   • Embedded
     • Computers are not limited to just PCs, tablets ect.
     • Processors exist on in almost limitless list of devices, e.g car engine management, washing machines etc..
     • Embedded OS tend to run on dedicated hardware so they run with max efficiency using low-powered processors and little memory
   • Real-time
     • In safety-critical environments such as aircraft autopiloting processes have to be guaranreed to execute within a know time
     • Plenty of redundany is built into these sytems si tgey can handle sudden increases in inputs. Hence, they hardly ever run at capacity