An OS is a collection programs and utilities, OS is the interface between user and computer. It creates the user-friendly environment. It is the main function of OS. Another main function of OS is resource management.
A Computer System has many resources (Hardware and Software) which may be required to complete a task. Software refers to the programs written to provide services to the users of the systems. Hardware refers to the physical computing equipment. The commonly required resources are input/output devices, Memory, file storage space, CPU and time.
The OS acts as the manager of these resources and allocates them to specific programs and users as necessary for their tasks. So, We can say that an OS as a resource allocator. Same as the OS collects the resources from the network environment or within a system and grants the resources to requesting jobs.
When several computers connected through a network and more than one computer trying for a common printer, or a common resource then the OS follow some order and efficiently manage the resources. Generally, the resource is a time-sharing resource, the first one of the task gets the resource for some time than another.
Structure of Operating System:
The structure of OS consists 4 layers. These are hardware, software, systems programs, application programs.
The hardware part consists of CPU, Main Memory, I/O Devices, Secondary Storage, etc. The software includes process management routines, memory management routines, I/O controls routines, file management routines. The system programs layer consisting of compilers, Assemblers, linker, etc. The application programs depend on users.
Mac Operating System :
Windows Operating System :