Sytem Components

OPERATING SYSTEMS PROCESS MANAGEMENT
~ A process is a program in execution. A process needs
certain resources, including CPU time, memory, files, and
I/O devices, to accomplish its task.

~ The operating system is responsible for the following
activities in connection with process management.
> Process creation and deletion.
> process suspension and resumption.
> Provision of mechanisms for:
-> process synchronization
-> process communication

MAIN MEMORY MANAGEMENT
~ Memory is a large array of words or bytes, each with its
own address. It is a repository of quickly accessible data
shared by the CPU and I/O devices.

~ Main memory is a volatile storage device. It loses its
contents in the case of system failure.

~ The operating system is responsible for the following
activities in connections with memory management:
> Keep track of which parts of memory are currently being
used and by whom.
> Decide which processes to load when memory space
becomes available.
> Allocate and deallocate memory space as needed.

FILE MANAGEMENT
~ A file is a collection of related information defined by its
creator. Commonly, files represent programs (both
source and object forms) and data.

~ The operating system is responsible for the following
activities in connections with file management:
> File creation and deletion.
> Directory creation and deletion.
> Support of primitives for manipulating files and directories.
> Mapping files onto secondary storage.
> File backup on stable (nonvolatile) storage media.

I/O SYSTEM MANAGEMENT
~ The I/O system consists of:
> A buffer-caching system
> A general device-driver interface
> Drivers for specific hardware devices

SECONDARY STORAGE MANAGEMENT
~ Since main memory (primary storage) is volatile and too
small to accommodate all data and programs
permanently, the computer system must provide
secondary storage to back up main memory.

~ Most modern computer systems use disks as the
principle on-line storage medium, for both programs and
data.

~ The operating system is responsible for the following
activities in connection with disk management:
> Free space management
> Storage allocation
> Disk scheduling

PROTECTION SYSTEM
~ Protection refers to a mechanism for controlling access
by programs, processes, or users to both system and
user resources.

~ The protection mechanism must:
> distinguish between authorized and unauthorized usage.
> specify the controls to be imposed.
> provide a means of enforcement.

COMMAND INTERPRETER SYSTEM
~ Many commands are given to the operating system by
control statements which deal with:
> process creation and management
> I/O handling
> secondary-storage management
> main-memory management
> file-system access
> protection
> networking