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2. Operating System - Types



Batch Operating System: The users of a batch operating system do not interact with the computer directly. Each user prepares his job on an off-line device like punch cards and submits it to the computer operator. To speed up processing, jobs with similar needs are batched together and run as a group. 

Time-Sharing Operating System: Time-sharing is a technique that enables many people, located at various terminals, to use a particular computer system at the same time. Processor's time which is shared among multiple users simultaneously is termed as time-sharing. The objective is to minimize response time. Multiple jobs are executed by the CPU by switching between them.
 
Distributed Operating System: Distributed systems use multiple central processors to serve multiple real-time applications and multiple users. Data processing jobs are distributed among the processors accordingly. The processors communicate with one another through various communication lines (such as high-speed buses or telephone lines). These processors are referred to as sites, nodes, computers, and so on. If one site fails in a distributed system, the remaining sites can potentially continue operating.
 
Network Operating System: A Network Operating System runs on a server and provides the server the capability to manage data, users, groups, security, applications, and other networking functions. The primary purpose of the network operating system is to allow shared file and printer access among multiple computers in a network, typically a local area network (LAN), and a private network or to 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. 
 
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 response time is very less as compared to online processing.
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.
 
Hard Real-Time Systems: Hard real-time systems guarantee that critical tasks are completed 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.
 
Soft Real-Time System: 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.  




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