Services of Operating System -
An operating system serves two main purposes:
Program Environment: It creates a suitable space for programs to run
smoothly.
User Convenience: It offers users a convenient way to run
programs.
Here are some typical services that an operating system provides:
- Program
execution
- I/O operations
- File System
manipulation
- Communication
- Error Detection
- Resource
Allocation
- Protection
Program Execution: Running
Programs
An operating system is like a traffic director for your computer.
It makes sure that when you want to use a program, it gets loaded into the
computer's memory and runs properly. It also ensures that different programs
don't bump into each other.
I/O Operations: Input and Output
Handling
Think of your computer as a big conversation. You tell it what to
do (input), and it responds (output). The operating system manages this
conversation, whether it's clicking a mouse, typing on a keyboard, or printing
a document.
File System Manipulation:
Organizing Files and Folders
Your computer stores files, like documents and pictures. The
operating system helps you put these files into folders so you can find them
easily. It also decides who can open, change, or delete these files and
folders.
Communication: Making Devices Talk
If you have different gadgets like phones, computers, and
printers, they need to talk to each other. The operating system acts like a
translator, making sure these devices understand each other so they can work
together.
Error Detection: Finding and
Fixing Mistakes
Just like spell-check in your writing, the operating system
constantly looks for errors in your computer. If it finds any, it tries to
correct them to keep your computer running smoothly.
Resource Allocation: Sharing
Computer Resources
Imagine your computer is like a pizza. Different programs want a
slice of it, but there's only so much to go around. The operating system
decides who gets how much, so everyone gets their fair share of resources like
memory and processing power.
Protection: Keeping Things Safe
When multiple people use a computer, the operating system acts
like a security guard. It makes sure that one person can't snoop on another
person's stuff or mess up their work. It keeps everything safe and separate.
Properties Of Operating
System
Following are the different properties of an Operating System. This tutorial
will explain these properties in detail one by one:
1. Batch
processing
2. Multitasking
3. Multiprogramming
4. Interactivity
5. Real
Time System
6. Distributed
Environment
7. Spooling
Batch processing
Batch processing is a technique in which an
Operating System collects the programs and data together in a batch before
processing starts. An operating system does the following activities related to
batch processing −
·
The OS defines a job which has
predefined sequence of commands, programs and data as a single unit.
·
The OS keeps a number a jobs in
memory and executes them without any manual information.
·
Jobs are processed in the order of
submission, i.e., first come first served fashion.
· When a job completes its execution, its memory is released and the output for the job gets copied into an output spool for later printing or processing.
Advantages
·
Batch processing takes much of the
work of the operator to the computer.
·
Increased performance as a new job
get started as soon as the previous job is finished, without any manual
intervention.
Disadvantages
- Difficult to debug program.
- A job could enter an infinite loop.
- Due to lack of protection scheme, one batch job can
affect pending jobs.
Multitasking
Multitasking is when multiple jobs are
executed by the CPU simultaneously by switching between them. Switches occur so
frequently that the users may interact with each program while it is running.
An OS does the following activities related to multitasking −
·
The user gives instructions to the
operating system or to a program directly, and receives an immediate response.
·
The OS handles multitasking in the
way that it can handle multiple operations/executes multiple programs at a
time.
·
Multitasking Operating Systems are
also known as Time-sharing systems.
·
These Operating Systems were
developed to provide interactive use of a computer system at a reasonable cost.
·
A time-shared operating system uses
the concept of CPU scheduling and multiprogramming to provide each user with a
small portion of a time-shared CPU.
· Each user has at least one separate program in memory.
·
A program that is loaded into memory
and is executing is commonly referred to as a process.
·
When a process executes, it typically
executes for only a very short time before it either finishes or needs to
perform I/O.
·
Since interactive I/O typically runs
at slower speeds, it may take a long time to complete. During this time, a CPU
can be utilized by another process.
·
The operating system allows the users
to share the computer simultaneously. Since each action or command in a
time-shared system tends to be short, only a little CPU time is needed for each
user.
·
As the system switches CPU rapidly
from one user/program to the next, each user is given the impression that
he/she has his/her own CPU, whereas actually one CPU is being shared among many
users.
Multiprogramming
Sharing the processor, when two or more
programs reside in memory at the same time, is referred as multiprogramming.
Multiprogramming assumes a single shared processor. Multiprogramming increases
CPU utilization by organizing jobs so that the CPU always has one to execute.
The following figure shows the memory layout for a multiprogramming system.
An OS does
the following activities related to multiprogramming.
·
The operating system keeps several
jobs in memory at a time.
·
This set of jobs is a subset of the
jobs kept in the job pool.
·
The operating system picks and begins
to execute one of the jobs in the memory.
·
Multiprogramming operating systems
monitor the state of all active programs and system resources using memory
management programs to ensures that the CPU is never idle, unless there are no
jobs to process.
Advantages
- High and efficient CPU utilization.
- User feels that many programs are allotted CPU
almost simultaneously.
Disadvantages
- CPU scheduling is required.
- To accommodate many jobs in memory, memory
management is required.
Interactivity
Interactivity refers to the ability of users
to interact with a computer system. An Operating system does the following
activities related to interactivity −
- Provides the user an interface to interact with the system.
- Manages input devices to take inputs from the user. For example, keyboard.
- Manages output devices to show outputs to the user. For example, Monitor.
The response time of the OS needs to be
short, since the user submits and waits for the result.
Real Time System
Real-time systems are usually dedicated,
embedded systems. An operating system does the following activities related to
real-time system activity.
- In such systems, Operating Systems typically read from and react to sensor data.
- The Operating system must guarantee response to events within fixed periods of time to ensure correct performance.
Distributed Environment
A distributed environment refers to multiple
independent CPUs or processors in a computer system. An operating system does
the following activities related to distributed environment −
·
The OS distributes computation logics
among several physical processors.
·
The processors do not share memory or
a clock. Instead, each processor has its own local memory.
·
The OS manages the communications
between the processors. They communicate with each other through various
communication lines.
Spooling
Spooling is an acronym for simultaneous
peripheral operations on line. Spooling refers to putting data of various I/O
jobs in a buffer. This buffer is a special area in memory or hard disk which is
accessible to I/O devices.
An operating system does the following
activities related to distributed environment −
·
Handles I/O device data spooling as
devices have different data access rates.
·
Maintains the spooling buffer which
provides a waiting station where data can rest while the slower device catches
up.
· Maintains parallel computation because of spooling process as a computer can perform I/O in parallel fashion. It becomes possible to have the computer read data from a tape, write data to disk and to write out to a tape printer while it is doing its computing task.
Advantages
- The spooling operation uses a disk as a very large buffer.
- Spooling is capable of overlapping I/O operation for one job with processor operations for another job.
