In this blog, we discussed an Introduction about Operating System
Operating System
OS Goals
– Control/execute user programs.
– Make the computer system convenient to use.
– Ease the solving of user problems.
– Use the computer hardware in an efficient manner.
Characteristics of OS
• It manages different resources like cpu, disk,
memory etc.
• It allows portability and enables easier
program.
• It improves the performance.
• It is an interface b/w hardware and software.
Kernel mode and User mode
• Kernel mode refers to the processor mode that enables
software to have full and unrestricted access to
the system and its resources.
• it is used to
access the hardware components and schedule
which processes should run on a computer system and
when, and it also manages the application software and
hardware interaction.
• Kernel mode is
also known as the master mode, privileged mode, or system mode.
• User Mode is a restricted mode,
which the application programs are executing and starts. User
mode is also known as the unprivileged mode.
Services provided by an OS
• Program Development :-
It provides variety of facilities and services
such as editor and debugger. Editor is used to
create or modify the program. Debugger is
used to debug the program.
• Program execution :-
It provides some tasks to execute program.
Instruction and data must be loaded into main
memory, I/O devices must be initialised and
resources must be prepared.
• Access to I/O devices :-
It requires some set of instructions or operations.
Programmer can access such devices using simple
reads and writes.
• System access :-
In the case of share or public system, OS
control access to the system. It must provide
protection from unauthorized user.
• Control access to Files :- Provide mechanism to control access to files.
• Error detection and correction :- A variety of error can occur while system is running
such as internal or external error. OS must correct
this type of errors.
• Accounting :- Accounting is the process of keeping track of a
user’s activity while accessing a network’s
resources, including the amount of time spent in the
network.
Type of Operating System
• Batch Operating System
• Real Time Operating System (RTOS)
• Multi user Operating System
• Time Sharing Operating System
• Distributed Operating System
Batch Operating System
• The user of batch operating system do not
interact with the computer directly. Each user
prepares his job on an off-line device like
punch cards and submit it to the computer
operator.
• To speed up the processing, jobs are batched
together and run as group. The operator sort out
programs into batches with similar
requirements.
• Examples: Payroll System, Bank Statements
• Disadvantages:-
1) Lack of interaction b/w user and job
2) CPU is often idle
3) Difficult to provide the priority
Real Time Operating System(RTOS)
• In this Response Time is already fixed.
• Real Time System is used at those Places in
which we Requires higher and Timely
Response.
• RTOS are used to control machinery, scientific
instruments and industrial systems.
• It act as a control device in dedicated
application.
• A very important part of an RTOS is managing
the resources of the computer so that a
particular operation executes in exactly the
same amount of time, every time it occurs.
• Examples: Scientific experiments, medical
imaging systems, industrial control systems,
robots, air traffic control systems etc.
There are two type of Real Time Operating
System:
1) Hard Real Time Operating System:-
- It has well defined and fixed time constraints.
- Processing must be done in defined
constraints otherwise system will fail.
2) Soft Real Time Operating System:-
- It has less time constraints and do not support
deadline scheduling.
Multi User Operating System
• A multi-user operating system allows multiple
users to access the data and processes of a
single machine from different computers or
terminals.
• Multi-user operating system is often used in
businesses and offices where different users
need to access the same resources, but these
resources cannot be installed on every system.
• In a multi-user operating system, the OS must
be able to handle the various needs and requests
of all of the users effectively.
• It is quite complicated and must be able to
properly manage the necessary tasks required
by the different users connected to it.
• Unix, VMS and mainframe operating systems
are examples of multi-user operating systems.
Time Sharing Operating System
• Processor’s time which is shared among multiple users
simultaneously is called time sharing operating
system.
• A time sharing system allows many users to share
the computer resources simultaneously.
• As the system switches rapidly from one user to the
other, a short time slot is given to each user for their
executions.
• Each user has given time slice.
• It is also known as multitasking or multiprogramming.
• Advantages:-
- Quick response time
- avoid duplication of software
- reduce cpu ideal time
• Disadvantages:-
- Problem of reliability
- Question of security
- Problem of data communication
Distributed Operating System
• A distributed system is a collection of
independent computers that appear to the users
of the system as a single system.
• Examples:
– Network of workstations
– Distributed manufacturing
– Network of branch office computers(Bank)
• Advantages:-
– Data sharing: allow many users to access to a
common data base
– Resource Sharing: expensive peripherals like
color printers
– Communication: enhance human-to-human
communication, e.g., email, chat
– Flexibility: spread the workload over the
available machines
• Disadvantages:-
– Software: difficult to develop software for
distributed systems
– Security: easy access also applies to secrete
data
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