Definition of Operating System:
An Operating system is a program that controls the execution of application programs and acts as an interface between the user of a computer and the computer hardware.
Examples of computer operating systems
Microsoft Windows 7 - PC and IBM compatible operating system. Microsoft Windows is the most commonly found and used operating system.
Apple MacOS - Apple computer operating system. The only Apple computer operating system.
Ubuntu Linux - A popular variant of Linux used with PC and IBM compatible computers.
Google Android - operating system used with Android compatible phones.
iOS - Operating system used with the Apple iPhone.
views
Three views of an operating system
1.Application View:what services does it provide?
2.System View:what problems does it solve?
3.Implementation View:how is it built?
Application View of an Operating System
The OS provides an execution environment for running programs.
*The execution environment provides a program with the processor time and memory space that it needs to run.
*The execution environment provides interfaces through which a program can use networks, storage, I/O devices, and other system hardware components.
** interfaces provide a simplified, abstract view of hardware to applicationprograms.
*The execution environment isolates running programs from one another and prevents undesirable interactions among them.
System View:
The OS manages the hardware resources of a computer system.
* Resources include processors, memory, disks and other storage devices,network interfaces, I/O devices such as keyboards, mice and monitors, and so on.
*The operating system allocates resources among running programs. It controls the sharing of resources among programs.
*The OS itself also uses resources, which it must share with application program
Implementation View
*Concurrency arises naturally in an OS when it supports concurrent applications, and because it must interact directly with the hardware
*Hardware interactions also impose timing constraints
Operating system goals:
1.Execute user programs and make solving user problems easier
2.Make the computer system convenient to use
3.Use the computer hardware in an efficient manner
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