Types of Operating System

Operating systems are there from the very first computer generation and they keep evolving with time. Some of the important types of operating systems that are most commonly used are:

i. Batch Operating System

This type of operating system does not interact with the computer directly. There is an operator which takes similar jobs having the same requirement and groups them into batches. It is the responsibility of the operator to sort the jobs with similar needs.

 fig. Batch Operating System[/caption]

Advantages of Batch Operating System:

• It is very difficult to guess or know the time required by any job to complete. Processors of
  the batch systems know how long the job would be when it is in the queue.
• Multiple users can share the batch systems.
• The idle time batch system is very less.
• It is easy to manage large work repeatedly in batch systems.

Disadvantages of Batch Operating System:

•  The computer operators should be well known with batch systems.
•  Batch systems are hard to debug.
•  It is sometimes costly.
• The other jobs will have to wait for an unknown time if any job fails.
• Examples of Batch-based Operating System: Payroll System, Bank Statements, etc.

ii. Time-Sharing Operating Systems

Each task has given some time to execute so that all the tasks work smoothly. Each user gets the time of CPU as they use a single system. These systems are also known as Multitasking Systems. The task can be from a single user or from different users also. The time that each task gets to execute is called quantum. After this time interval is over OS switches over to the next task.

Advantages of Time-Sharing OS:

• Each task gets an equal opportunity.
• Fewer chances of duplication of software.
• CPU idle time can be reduced.

Disadvantages of Time-Sharing OS:

•  Reliability problem.
• One must have to take care of the security and integrity of user programs and data.
• Data communication problem.
• Examples of Time-Sharing OSs are Multics, Unix, etc.

iii. Distributed Operating System

These types of the operating system is a recent advancement in the world of computer technology and are being widely accepted all over the world and, that too, with a great pace. Various autonomous interconnected computers communicate with each other using a shared communication network. Independent systems possess their own memory unit and CPU. These are referred to as loosely coupled systems or distributed systems. These system's processors differ in size and function. The major benefit of working with these types of the operating system is that it is always possible that one user can access the files or software which are not actually present on his system but on some
other system connected within this network i.e., remote access is enabled within the devices connected in that network.

Advantages of Distributed Operating System:

• Failure of one will not affect the other network communication, as all systems are independent
  from each other.
•  Electronic mail increases the data exchange speed.
•  Since resources are being shared, computation is highly fast and durable.
•  Load on host computer reduces.
• These systems are easily scalable as many systems can be easily added to the network.
• Delay in data processing reduces.

Disadvantages of Distributed Operating System:

•  Failure of the main network will stop the entire communication.
• To establish distributed systems, the language which is used is not well defined yet.
• These types of systems are not readily available as they are very expensive. Not only that the
  underlying software is highly complex and not understood well yet.
• Examples of Distributed Operating systems are- LOCUS, AMOEBA, etc.

iv. Network Operating System

These systems run on a server and provide the capability to manage data, users, groups, security, applications, and other networking functions. These type of operating systems allows shared access of files, printers, security, applications, and other networking functions over a small private network. One more important aspect of Network Operating Systems is that all the users are well aware of the underlying configuration, of all other users within the network, their individual connections, etc. and that’s why these computers are popularly known as tightly coupled systems.

 fig. Network Operating System[/caption]

Advantages of Network Operating System:

• Highly stable centralized servers.
• Security concerns are handled through servers.
• New technologies and hardware up-gradation are easily integrated into the system.
• Server access is possible remotely from different locations and types of systems.

Disadvantages of Network Operating System:

•  Servers are costly.
•  The user has to depend on the central location for most operations.
• Maintenance and updates are required regularly.
• Examples: Microsoft Windows Server 2003, Microsoft Windows Server 2008, UNIX, Linux, Mac
  OS X, Novell NetWare, and BSD, etc.

v. Parallel Operating System

•  Paralleloperatingsystemsareusedtointerfacemultiplenetworkedcomputerstocompletetasksinparallel.The architecture of the software is often a UNIX-based platform, which allows it to coordinate distributed loads between multiple computers in a network.
•  Parallel operating systems are able to use software to manage all of the different resources of the computers
  running in parallels, such as memory, caches, storage space, and processing power.
•  Parallel operating systems also allow a user to directly interface with all of the computers in the network.
• A parallel operating system works by dividing sets of calculations into smaller parts and distributing them between the machines on a network. To facilitate communication between the processor cores and memory arrays, routing software has to either share its memory by assigning the same address space to all of the networked computers or distribute its memory by assigning different address space to each processing core.

vi. Real-Time Operating System

A real-time system is defined as a data processing system in which the time interval required to process and respond to inputs is so small that it controls the environment. The time taken by the system to respond to an input and display of required updated information is termed the response time. So in this method, the response time is very less as compared to online processing. Real-time systems are used when there are rigid time requirements on the operation of a processor or the flow of data and real-time systems can be used as a control device in a dedicated application.

A real-time operating system must have well-defined, fixed time constraints, otherwise, the system
will fail. For example, Scientific experiments, medical imaging systems, industrial control systems, weapon systems, robots, air traffic control systems, etc.

Advantages of Real-Time Operating System:

•  Maximum Consumption
•  Task Shifting
•  Error Free
•  24-7 systems

Disadvantages of Real-Time Operating System:

•  Limited Tasks
•  Use heavy system resource
•  Complex Algorithms
•  Expensive

There are two types of real-time operating systems.

I. Hard real-time systems
Hard real-time systems guarantee that critical tasks complete on time. In hard real-time systems, secondary storage is limited or missing and the data is stored in ROM. In these systems, virtual memory is almost never found.

II. Soft real-time systems
Soft real-time systems are less restrictive. A critical real-time task gets priority over other tasks and retains the priority until it completes. Soft real-time systems have limited utility than hard real-time systems. For example, multimedia, virtual reality, Advanced Scientific Projects like undersea exploration and planetary rovers, etc.