Types of Operating Systems | Principles of operating System
Operating system is defined as a collection of programs which controls and co-ordinates resources of a computer system. Resource can be a hardware or software. Resources refer to peripheral devices (such as input, output devices, memory etc). The term peripheral refer to Input/Output devices. Operating systems are usually written in low level languages such as C programming.
TYPES OF OPERATING SYSTEMS
- Batch Operating System
- Time-sharing system
- Distributed Operating System
- Network Operating System
- Real-time Operating System
BATCH OPERATING SYSTEM
Batch is defined as group of jobs with similar needs. Example is printing several jobs from different users. The operating system allows user to form batches. Computer executes each BATCH sequentially. In a batch system, user enters input on punched cards. The input collected is read onto a magnetic tape using a computer.
In batch system, user does not intact with the computer directly. User submits the job to the operator and such an operator collects jobs from various users. Thus operator prepares a batch of jobs. Programmers also leave their programs with operator. The batch of similar jobs or similar programs would be processed when computer time is available. After execution of the job or program, O/P would be sent to the appropriate user or programmer.
The users of the Batch OS do not interact with the computer directly. Each user prepares his job on an OFF-LINE device like punched cards & submits it to the computer operator. Punched cards are older form of data storage. To speedup processing, jobs with similar needs are batched together and run as a group. User submits their programs to the operator. The operator then sorts programs into batches with similar requirements.
In batch system execution, CPU utilization is not proper and CPU is often idle, because most of the computing jobs involve I/O operations. Main disadvantage of Batch OS is lack of interaction between user and job.
DISTRIBUTED OPERATING SYSTEM
Distributed Operating System is a model where distributed applications are running on multiple computers linked by communications. In distributed operating system the computing power is distributed among different processors of different computers. These systems are loosely coupled meaning they have their own resources. These systems vary in size, speed and computation power. These systems communicate with each other via communication line over the network.
With the advent of computer networks, in which many computers are linked together and are able to communicate with one another, distributed computing became feasible. A distributed computation is one that is carried out on more than one machine in a cooperative manner. A group of linked computers working cooperatively on tasks, referred to as a distributed system, often requires a distributed operating system to manage the distributed resources.
Distributed systems provide the following advantages:
- Sharing of resources
- Reliability
- Communication
- Computation speedup
NETWORK OPERATING SYSTEM
A network operating system is an operating system designed for the sole purpose of supporting workstations, database sharing, application sharing and file and printer access sharing among multiple computers in a network. Certain operating systems, such as Microsoft Windows NT and Digital’s OpenVMS, come with multipurpose capabilities and can also act as network operating systems. Some of the most well-known network operating systems include Microsoft Windows Server 2003, Microsoft Windows Server 2008, UNIX, Linux and Mac OS X. A network operating system includes special functions for connecting computers and devices into local-area network (LAN).
A network operating system (NOS) provides services to clients over a network. In network operating systems the files and printers are shared among different computers. The software updates are also shared among different computers. The popular examples of network operating system is Microsoft windows server 2003, 2008, unix and linux.
Common tasks associated with network operating systems include:
- Providing access to remote printers,
- Enabling and managing access to files on remote systems, and determining who can access what
- Granting access to remote applications and resources, such as the Internet
- Monitoring the system and security, so as to provide proper security against viruses, hackers, and data corruption.
- Providing basic network administration
- System maintenance activities like backup
REAL-TIME OPERATING SYSTEM (RTOS)
Remember: A correct answer obtained after expiry of time is as bad as wrong answer.
In general, an operating system (OS) is responsible for managing the hardware resources of a computer and hosting applications that run on the computer. An RTOS performs these tasks, but is also specially designed to run applications with very precise timing and a high degree of reliability. This can be especially important in measurement and automation systems.
Real time systems are classified into two categories:
Soft Real Time System
If certain deadlines are missed, then system continues its working with no failure but its performance degrades. These are risky to use for industrial control and robotics.
Hard real time systems
If any deadline is missing then system will fail to work or does not work properly.
The system guarantees that critical tasks are completed on time. Virtual memory is never found in a real time system. So, hard real time systems conflicts with the operation of time-sharing systems, and the two cannot be mixed.
Real time operating systems are used in large organizations while network and distributed operating systems are most common in middle and large organizations. Some of the most widely used RTOS are:
- LynxOS
- VxWorks
- Windows CE
- RTLinux
- QNX
