Introduction to operating System�and Its Types

Mrs. Sangeeta Bhandari

HMV, Jalandhar

Operating System

• An operating system acts as an intermediary between the user of a computer and computer hardware.
• The purpose of an operating system is to provide an environment in which a user can execute programs conveniently and efficiently. 

Operating System

• An operating system is a software that manages computer hardware.
• An operating system is concerned with the allocation of resources and services, such as memory, processors, devices, and information
• Windows, Unix, Linux, Mac, android etc.

Operating System Goals

• Execute user programs and make solving user problems easier
• Make the computer system convenient to use
• Use the computer hardware in an efficient manner

Computer System Structure

• Computer system can be divided into four components
• Hardware – provides basic computing resources - CPU, memory, I/O devices
• Operating system
• Controls and coordinates use of hardware among various applications and users
• Application programs

– define the ways in which the system resources are used to solve the computing problems of the users

Word processors, compilers, web browsers, database systems, video games

• Users

People, machines, other computers

Operating System - Examples

• Windows: This is one of the most popular and commercial operating systems developed and marketed by Microsoft. It has different versions in the market like Windows 8, Windows 10 etc and most of them are paid.
• Linux This is a Unix based and the most loved operating system first released on September 17, 1991 by Linus Torvalds. Today, it has 30+ variants available like Fedora, OpenSUSE, CentOS, UBuntu etc. Most of them are available free of charges though you can have their enterprise versions by paying a nominal license fee.

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Operating System - Examples

• MacOS This is again a kind of Unix operating system developed and marketed by Apple Inc. since 2001.
• iOS This is a mobile operating system created and developed by Apple Inc. exclusively for its mobile devices like iPhone and iPad etc.
• Android This is a mobile Operating System based on a modified version of the Linux kernel and other open source software, designed primarily for touchscreen mobile devices such as smartphones and tablets.

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Functions of Operating System

Functions: Process management

Process management helps OS to create and delete processes. It also provides mechanisms for synchronization and communication among processes.

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Functions: Memory management

• Memory management module performs the task of allocation and de-allocation of memory space to programs in need of this resources.
• File management :It manages all the file-related activities such as organization storage, retrieval, naming, sharing, and protection of files.

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Functions: Device Management

• Device management keeps tracks of all devices. This module also responsible for this task is known as the I/O controller. It also performs the task of allocation and de-allocation of the devices.
• I/O System Management: One of the main objects of any OS is to hide the peculiarities of that hardware devices from the user.

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Functions: Secondary-Storage Management

• Systems have several levels of storage which includes primary storage, secondary storage, and cache storage. Instructions and data must be stored in primary storage or cache so that a running program can reference it.

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Functions: Security

• Security module protects the data and information of a computer system against malware threat and authorized access.
• Command interpretation: This module is interpreting commands given by the and acting system resources to process that commands.

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Functions: Networking

• A distributed system is a group of processors which do not share memory, hardware devices, or a clock. The processors communicate with one another through the network.
• Job accounting: Keeping track of time & resource used by various job and users.

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Communication management

• Coordination and assignment of compilers, interpreters, and another software resource of the various users of the computer systems.

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Types of operating systems

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.
• The programmers leave their programs with the operator and the operator then sorts the programs with similar requirements into batches.
• The problems with Batch Systems are as follows −
• Lack of interaction between the user and the job.
• CPU is often idle, because the speed of the mechanical I/O devices is slower than the CPU.
• Difficult to provide the desired priority.

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Types of operating systems

• Time-sharing is a technique which enables many people, located at various terminals, to use a particular computer system at the same time.
• The main difference between Multiprogrammed Batch Systems and Time-Sharing Systems is that in case of Multiprogrammed batch systems, the objective is to maximize processor use, whereas in Time-Sharing Systems, the objective is to minimize response time.

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Types of operating systems

• Multiple jobs are executed by the CPU by switching between them, but the switches occur so frequently. Thus, the user can receive an immediate response. For example, in a transaction processing, the processor executes each user program in a short burst or quantum of computation.

Types of operating systems

• Advantages of Timesharing operating systems are as follows −
• Provides the advantage of quick response.
• Avoids duplication of software.
• Reduces CPU idle time.
• Disadvantages of Time-sharing operating systems are as follows −
• Problem of reliability.
• Question of security and integrity of user programs and data.
• Problem of data communication.

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Types of operating systems

• Advantages of Timesharing operating systems are as follows −
• Provides the advantage of quick response.
• Avoids duplication of software.
• Reduces CPU idle time.
• Disadvantages of Time-sharing operating systems are as follows −
• Problem of reliability.
• Question of security and integrity of user programs and data.
• Problem of data communication.

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Types of operating systems

• 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). Processors in a distributed system may vary in size and function. These processors are referred as sites, nodes, computers, and so on.

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Types of operating systems

• The advantages of distributed systems are as follows −
• With resource sharing facility, a user at one site may be able to use the resources available at another.
• Speedup the exchange of data with one another via electronic mail.
• If one site fails in a distributed system, the remaining sites can potentially continue operating.
• Better service to the customers.
• Reduction of the load on the host computer.
• Reduction of delays in data processing.

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Types of operating systems

• 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.
• Examples of network operating systems include Microsoft Windows Server 2003, Microsoft Windows Server 2008, UNIX, Linux, Mac OS X, Novell NetWare, and BSD.

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Types of operating systems

• The advantages of network operating systems −
• Centralized servers are highly stable.
• Security is server managed.
• Upgrades to new technologies and hardware can be easily integrated into the system.
• Remote access to servers is possible from different locations and types of systems.

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• The disadvantages of network operating systems −
• High cost of buying and running a server.
• Dependency on a central location for most operations.
• Regular maintenance and updates are required.

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Types of operating systems

• 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.
• 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.
• Soft real-time systems are less restrictive. A critical real-time task gets priority over other tasks and retains the priority until it completes.

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