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There are operating systems from the very first generation of computers and they continue to develop over time. In this chapter, we will discuss some of the most widely used significant types of operating systems.
Batch operating system users aren't specifically interacting with the computer. Each user prepares his job, like punch cards, on an off-line system and submits it to the computer operator. Jobs with common needs are batched together to speed up processing and run as a group. The programmers leave the operator with their programmes, and the operator then sort the programmes with similar requirements into batches.
Batch Systems problem is as follows –
Time-sharing is a technique that allows several users to simultaneously use a particular computer system, located at different terminals. Multiprogramming is a functional extension of time-sharing or multitasking. The time that is shared by multiple users at the same time is called time-sharing.
The key difference between Multi programmed Batch Systems and Time-Sharing Systems is that in the case of Multi programmed batch systems, the target is to optimise processor utilisation, while in Time-Sharing Systems the goal is to reduce response time.
The Processor executes several jobs by switching between them, but the switches only occur too often. So the user can get an immediate answer. For example, the processor executes each user programme in a short burst or a quantity of computation in a transaction processing. That is, each user can get a quantum time if n users are present.
The operating system uses CPU scheduling and multiprogramming to produce a specific portion of time for each user. Computer systems that were originally configured as batch systems were changed to time-sharing systems.
Timesharing operating systems have the following benefits −
Time-sharing operating systems have the following disadvantages-
Distributed systems use multiple central processors to support multiple applications and multiple users in real-time. Data processing jobs are accordingly distributed among the processors.
The processors communicate with each other through various lines of communication (such as high-speed buses or telephone lines). These are called loose linking or distributed systems. The size and role of the processors within a distributed system can vary. These processors are referred to as web pages, nodes, computers, etc.
Distributed systems profit as follows −
A network operating system runs on a server and gives the server the ability to handle data, users, groups, protection, applications and other networking functions. The network operating system's primary purpose is to allow shared file and printer access between multiple computers in a network, usually a local area network ( LAN), a private network or other networks.
Examples of network operating systems include Microsoft Windows Server 2003, Microsoft Windows Server 2008, UNIX, Linux, Mac OS X, Novell NetWare, and BSD.
The network operating systems profit as follows −
The network operating systems have the following drawbacks −
A real-time system is characterised as a data processing system where the time period needed for processing and responding to inputs is so small that the environment is regulated. The system's delay in responding to input and showing the necessary updated information is called response time. The response time in this system is also much less than in online processing.
Real-time systems are used when the operation of a processor involves rigid time or data flow, and real-time systems may be used as a control device in a specialised programme. An operating system in real-time must have well-defined, fixed time constraints or the system would fail.
For example, Scientific experiments, medical imaging systems, industrial control systems, weapon systems, robots, air traffic control systems, etc.
There are two types of real-time operating systems.
Hard real-time systems ensure critical tasks are performed on time. Secondary storage is minimal or missing in hard-time real-time systems and the data is stored in ROM. Virtual memory is almost never contained in such systems.
Less rigid soft real-time systems. A vital task in real-time takes precedence over other tasks and holds the priority until it is complete. Soft real-time systems have little effectiveness compared to hard real-time systems. Multimedia, virtual reality, Advanced Research Projects such as exploration missions, planetary rovers etc.