OS Components

Processor Manager decides how to allocate the central processing unit (CPU)
Processor Manager has two levels of responsibility:
To handle jobs as they enter the system
Handled by Job Scheduler
To manage each process within those jobs
Handled by Process Scheduler

Memory Manager: In charge of main memory (RAM)
Responsibility includes:
Preserves the space in main memory occupied by the operating system
Checks the validity of each request for memory space
Sets up a table to keep track of who is using which section of memory in a multiuser environment
Deallocates memory when the time comes to reclaim the memory

Device Manager monitors every device, channel, and control unit
Responsibility includes:
Chooses the most efficient way to allocate all of the system’s devices, printers, terminals, disk drives, based on a scheduling policy
Makes the allocation, starts its operation
Deallocates the device

File Manager keeps track of every file in the system including data files, assemblers, compilers, and application programs
Responsibility includes:
Enforces restrictions on who has access to which files by using predetermined access
Controls what users are allowed to do with files once they access them
Allocates the resource by opening the file and deallocates it by closing the file

Operating systems with networking capability have a fifth essential manager called the Network Manager
Network Manager provides a convenient way for users to share resources while controlling users’ access to them. The resources include:
Hardware (such as CPUs, memory areas, printers, tape drives, modems, and disk drives)
Software (such as compilers, application programs, and data files)

To be more efficient, each of the subsystem manager must perform the following tasks:
Monitor its resources continuously
Enforce the policies that determine who gets what, when, and how much
Allocate the resource when it’s appropriate
Deallocate the resource when appropriate

Essential managers of an operating system:
Processor Manager
Memory Manager
Device Manager
File Manager
Network Manager
Each manager both works closely with the other managers and performs its unique role – Interprocess Communication Manager
User Command Interface is unique to each operating system

OS is a resource allocator
Processor ManageManages all resources
Decides between conflicting requests for efficient and fair resource use
OS is a control program
Controls execution of programs to prevent errors and improper use of the computer