Operating System - Overview
An
Operating System (OS) is an interface between a computer user and computer
hardware. An operating system is a software which performs all the basic tasks
like file management, memory management, process management, handling input and
output, and controlling peripheral devices such as disk drives and printers.
Some
popular Operating Systems include Linux, Windows, OS X, VMS, OS/400, AIX, z/OS,
etc.
Definition
An
operating system is a program that acts as an interface between the user and
the computer hardware and controls the execution of all kinds of programs.
Following
are some of important functions of an operating System.
- Memory
Management
- Processor
Management
- Device
Management
- File Management
- Security
- Control over
system performance
- Job accounting
- Error detecting
aids
- Coordination
between other software and users
Memory Management
Memory
management refers to management of Primary Memory or Main Memory. Main memory
is a large array of words or bytes where each word or byte has its own address.
Main
memory provides a fast storage that can be accessed directly by the CPU. For a
program to be executed, it must in the main memory. An Operating System does
the following activities for memory management −
· Keeps
tracks of primary memory, i.e., what part of it are in use by whom, what part
are not in use.
· In
multiprogramming, the OS decides which process will get memory when and how
much.
· Allocates
the memory when a process requests it to do so.
· De-allocates
the memory when a process no longer needs it or has been terminated.
Processor Management
In
multiprogramming environment, the OS decides which process gets the processor
when and for how much time. This function is called process scheduling. An
Operating System does the following activities for processor management −
· Keeps
tracks of processor and status of process. The program responsible for this
task is known as traffic controller.
· Allocates
the processor (CPU) to a process.
· De-allocates
processor when a process is no longer required.
Device Management
An
Operating System manages device communication via their respective drivers. It
does the following activities for device management −
· Keeps
tracks of all devices. Program responsible for this task is known as the I/O
controller.
· Decides
which process gets the device when and for how much time.
· Allocates
the device in the efficient way.
· De-allocates
devices.
File Management
A file
system is normally organized into directories for easy navigation and usage.
These directories may contain files and other directions.
An
Operating System does the following activities for file management −
· Keeps
track of information, location, uses, status etc. The collective facilities are
often known as file system.
· Decides
who gets the resources.
· Allocates
the resources.
· De-allocates
the resources.
Other Important Activities
Following
are some of the important activities that an Operating System performs −
· Security − By means of password and similar other
techniques, it prevents unauthorized access to programs and data.
· Control over system
performance − Recording delays between
request for a service and response from the system.
· Job accounting − Keeping track of time and resources used by
various jobs and users.
· Error detecting aids − Production of dumps, traces, error messages,
and other debugging and error detecting aids.
· Coordination between
other softwares and users − Coordination
and assignment of compilers, interpreters, assemblers and other software to the
various users of the computer systems.
