Write the short notes on operating systems and its types

Write the definition of computer operating systems and types

1. Operating Systems Dr. Shailendra Bhalawe Assistant Professor College of Agriculture Balaghat Jawaharlal Nehru Krashi Vishwavidyalaya Jabalpur (M.P.)

2. Operating System: An Operating System (OS) is an interface between computer user and computer hardware. An operating system is software which performs all the basic tasks like file management, memory management, process management, handling input and output, and controlling peripheral devices such as disk drives and printers. Some popular Operating Systems include DOS, Linux, Windows, Android , etc. Definition: An operating system is a program that acts as an interface between the user and the computer hardware and controls the execution of all kinds of programs.

3. History Of OS: Operating systems were first developed in the late 1950s to manage tape storage The General Motors Research Lab implemented the first OS in the early 1950s for their IBM 701 In the mid-1960s, operating systems started to use disks In the late 1960s, the first version of the Unix OS was developed The first OS built by Microsoft was DOS . It was built in 1981 by purchasing the 86-DOS software from a Seattle company The present-day popular OS Windows first came to existence in 1985 when a GUI was created and paired with MS-DOS.

4. Operating System Functions: Following are some of important functions of an operating System. Memory Management Processor Management Device Management File Management Security Control over system performance Job accounting Error detecting aids Coordination between other software and users

5. Memory Management: Memory management refers to management of Primary Memory or Main Memory. Main memory is a large array of words or bytes where each word or byte has its own address. Main memory provides a fast storage that can be accessed directly by the CPU. For a program to be executed, it must in the main memory. An Operating System does the following activities for memory management − Keeps tracks of primary memory, i.e., what part of it are in use by whom, what part are not in use. In multiprogramming, the OS decides which process will get memory when and how much. Allocates the memory when a process requests it to do so. De-allocates the memory when a process no longer needs it or has been terminated.

6. Unit of Measurements (Memory): Storage measurements: The basic unit used in computer data storage is called a bit ( binary digit). Computers use these little bits, which are composed of ones and zeros, to do things and talk to other computers. All your files, for instance, are kept in the computer as binary files and translated into words and pictures by the software (which is also ones and zeros). This two number system, is called a “binary number system” since it has only two numbers in it. The decimal number system in contrast has ten unique digits, zero through nine. Conversions: 8 Bit = 1 Byte 1024 or 2 10 Byte = 1KB ( KiloByte ) 1024 KB = 1MB ( MegaByte ) 1024 MB = 1GB ( GigaByte ) 1024 GB = 1TB ( TeraByte )

7. Processor Management: In multiprogramming environment, the OS decides which process gets the processor when and for how much time. This function is called  process scheduling . An Operating System does the following activities for processor management − Keeps tracks of processor and status of process. The program responsible for this task is known as  traffic controller . Allocates the processor (CPU) to a process. De-allocates processor when a process is no longer required.

8. Device Management: An Operating System manages device communication via their respective drivers. It does the following activities for device management − Keeps tracks of all devices. Program responsible for this task is known as the  I/O controller . Decides which process gets the device when and for how much time. Allocates the device in the efficient way. De-allocates devices.

9. File Management: A file system is normally organized into directories for easy navigation and usage. These directories may contain files and other directions. An Operating System does the following activities for file management − Keeps track of information, location, uses, status etc. The collective facilities are often known as  file system . Decides who gets the resources. Allocates the resources. De-allocates the resources.

10. Other Important Activities: Following are some of the important activities that an Operating System performs − Security  − By means of password and similar other techniques, it prevents unauthorized access to programs and data. Control over system performance  − Recording delays between request for a service and response from the system. Job accounting  − Keeping track of time and resources used by various jobs and users. Error detecting aids  − Production of dumps, traces, error messages, and other debugging and error detecting aids. Coordination between other softwares and users  − Coordination and assignment of compilers, interpreters, assemblers and other software to the various users of the computer systems.

11. 1. Batch processing: Batch processing is a technique in which an Operating System collects the programs and data together in a batch before processing starts. An operating system does the following activities related to batch processing − The OS defines a job which has predefined sequence of commands, programs and data as a single unit. The OS keeps a number a jobs in memory and executes them without any manual information. Jobs a re processed in the order of submission, i.e., first come first served fashion. When a job completes its execution, its memory is released and the output for the job gets copied into an output spool for later printing or processing.

12. Advantages Batch processing takes much of the work of the operator to the computer. Increased performance as a new job get started as soon as the previous job is finished, without any manual intervention. Disadvantages Difficult to debug program. A job could enter an infinite loop. Due to lack of protection scheme, one batch job can affect pending jobs.

13. 2. Multitasking : Multitasking is when multiple jobs are executed by the CPU simultaneously by switching between them. Switches occur so frequently that the users may interact with each program while it is running. An OS does the following activities related to multitasking − The user gives instructions to the operating system or to a program directly, and receives an immediate response. The OS handles multitasking in the way that it can handle multiple operations/executes multiple programs at a time. Multitasking Operating Systems are also known as Time-sharing systems. These Operating Systems were developed to provide interactive use of a computer system at a reasonable cost. A time-shared operating system uses the concept of CPU scheduling and multiprogramming to provide each user with a small portion of a time-shared CPU.

14. 3. Multi programming : Sharing the processor, when two or more programs reside in memory at the same time, is referred as  multiprogramming . Multiprogramming assumes a single shared processor. Multiprogramming increases CPU utilization by organizing jobs so that the CPU always has one to execute. An OS does the following activities related to multiprogramming. The operating system keeps several jobs in memory at a time. This set of jobs is a subset of the jobs kept in the job pool. The operating system picks and begins to execute one of the jobs in the memory. Multiprogramming operating systems monitor the state of all active programs and system resources using memory management programs to ensures that the CPU is never idle, unless there are no jobs to process.

15. Advantages High and efficient CPU utilization. User feels that many programs are allotted CPU almost simultaneously. Disadvantages CPU scheduling is required. To accommodate many jobs in memory, memory management is required.

16. 4. Multiprocessing Operating System In Multiprocessing, Parallel computing is achieved. There are more than one processors present in the system which can execute more than one process at the same time. This will increase the throughput of the system. In multiprocessing, several processors execute procedures in collaboration. You can even split a procedure into parts that run in parallel. Since several processors work concurrently, more tasks are completed faster . Multiprocessing enhances the speed at which the system executes since tasks scatter the processors, minimizing the waiting period for procedures. If one processor is faulty, the others will continue running, hence enhancing system reliability. Such an operating system is suited for highly computationally intensive environments needing high processing power, for example, scientific simulations, real-time data processing, and server environments

17. Advantages of Multiprocessing Operating System : Increased Reliability : Because multiple processors are present, if one fails, others may take over it, thus stabilizing the system. Increased Throughput : More jobs can be processed at the same time by these multiple processors than by a single processor, thereby increasing the speed of execution. Efficient Resource Utilization : It acts more productively upon the utilization of resources like CPU, memory, and I/O devices. Parallelism: Many processes can run parallel, which increases the speed of execution to a large extent. Scalability: As the workload increases, more processors can be added to enhance performance. Disadvantages of Multiprocessing Operating System: Complexity:  There is a rise in the complexity of the system while dealing with a number of processors and proper distribution of tasks. Increased Cost:  Hardware equipment added in multiprocessing systems increases their cost Communication Overhead:  Generally, communication among processors results in overhead and provides a slight reduction in efficiency. Software Compatibility Problems:  Generally, most software is not designed to operate properly with multiprocessing systems.

18. 5. Real Time System Real-time systems are usually dedicated, embedded systems. An operating system does the following activities related to real-time system activity. In such systems, Operating Systems typically read from and react to sensor data . The Operating system must guarantee response to events within fixed periods of time to ensure correct performance .

19. Advantages of Real-Time Operating System: Real-time applications are quite easy to design, develop, and implement under a real-time operating system. Maximum utilization of devices and systems in a Real-Time Operating System. Fast response to events. High reliability in the performance of time-critical operations. Strict scheduling ensures the predictable execution of tasks . Disadvantages of Real-Time Operating System: Real-time operating systems are very expensive to design. Real-time operating systems are very resource-intensive and consume critical CPU cycles. Less multitasking support. Lacks adaptability to new functions. At times, it demands specific hardware.

20. 6. Distributed Environment: A distributed environment refers to multiple independent CPUs or processors in a computer system. An operating system does the following activities related to distributed environment − The OS distributes computation logics among several physical processors. The processors do not share memory or a clock. Instead, each processor has its own local memory. The OS manages the communications between the processors. They communicate with each other through various communication lines.

21. Advantages of Distributed Operating System The distributed operating system offers resource sharing. This is a fault-tolerant system. Scalability is achieved and easily new nodes can be added to the system. Distributed task execution improves its performance. Parallel processing helps in increasing the speed of job execution and enhances efficiency in getting results . Disadvantages of Distributed Operating System Protocol overhead might control computation costs. The managing of the system is complex as it works in distributed. Security may prove difficult on multiple nodes. The system highly depends on network stability for it to run without hassles.

22. 7. Time-Sharing Operating System A Time-Sharing Operating System allows multiple users to access the system concurrently, and this occurs by allocating a small time slice or quantum to each task. The CPU switches between the tasks so rapidly that the users feel their programs have been running concurrently. This kind of operating system is most effective in systems where multiple users require access to the central system in real-time or near real-time . Here's how it works : Scheduling:  Operating systems use scheduling algorithms in order to allow a particular block of CPU time, referred to as a time slice, for each user or process. After each time slice, the CPU shifts to the following process in the queue. Multiprogramming:  The TSOS uses multiprogramming, where several programs are resident in the memory at any given time. This allows several programs to be executed simultaneously. Context Switching:  Whenever the CPU needs to switch to another task, the operating system saves the state of the current process and loads the state of the next process. It is a process referred to as context switching. That lets a task be resumed exactly where it left off.

23. Advantages of Time-Sharing Operating System The time-sharing operating system facilitates effective utilization and sharing of resources. This system helps decrease CPU idle and response time. It allows various users to access and interact with their programs at the same time, and it leads to greater productivity. Time-sharing assures better memory management because it swaps programs into and out of main memory efficiently. An interactive computing environment provides users with real-time access to their programs and files. Disadvantages of Time-Sharing Operating System Data transmission rates compared to others are very high The integrity and security of the user programs loaded in memory and data have to be ensured since many users access the system concurrently. Implementation as well as management of time-sharing systems is more complicated than others since there is a tendency for task scheduling and memory management. Since more and more users get hooked to the system, it degrades due to resource contention. However, with time, context switches between tasks will incur overheads, thereby impacting the overall efficiency of the system.

24.   8. 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 types of operating systems allow shared access to 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  .

25. 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. User has to depend on a central location for most operations. Maintenance and updates are required regularly.

26. Spooling: Spooling is an acronym for simultaneous peripheral operations on line. Spooling refers to putting data of various I/O jobs in a buffer. This buffer is a special area in memory or hard disk which is accessible to I/O devices. An operating system does the following activities related to distributed environment − Handles I/O device data spooling as devices have different data access rates. Maintains the spooling buffer which provides a waiting station where data can rest while the slower device catches up. Maintains parallel computation because of spooling process as a computer can perform I/O in parallel fashion. It becomes possible to have the computer read data from a tape, write data to disk and to write out to a tape printer while it is doing its computing task.

27. Examples of Operating System are –  Windows (GUI based, PC) GNU/Linux (Personal, Workstations, ISP, File and print server, Three-tier client/Server) MacOS (Macintosh), used for Apple’s personal computers and workstations ( MacBook , iMac). Android (Google’s Operating System for smartphones /tablets/ smartwatches ) iOS (Apple’s OS for iPhone , iPad , and iPod Touch)

28. MS-Windows: Microsoft Windows (also referred to as Windows or Win) is a graphical operating system developed and published by Microsoft. It provides a way to store files, run software, play games, watch videos, and connect to the Internet. Microsoft Windows was first introduced with version 1.0 on November 10, 1983. Over a dozen versions of Windows were released after that, including the current version, Windows 10.

29. Some versions of Windows Operating System: Windows 10 Windows 8 Windows 7 Windows Vista Windows XP Windows 2000 Windows NT Windows ME Windows 98 Windows 95

30. UNIX Operating System: Unix is an Operating System. It was developed in the 1970s by Ken Thompson, Dennis Ritchie, and others in the AT&T Laboratories. It was originally meant for programmers developing software rather than non-programmers. Unix and the C were found by AT&T and distributed to government and academic institutions, which led to both being ported to a wider variety of machine families than any other operating system. The main focus that was brought by the developers in this operating system was the Kernel. Unix was considered to be the heart of the operating System. System Structure of Unix OS is shown in below figure.

31. Unix Architecture

32. Linux: The Linux open source operating system, or Linux OS, is a freely distributable, cross-platform operating system based on Unix that can be installed on PCs, laptops, notebooks, mobile and tablet devices, video game consoles, servers, supercomputers and more. The official mascot of the Linux kernel is a penguin character named Tux. This Linux logo was suggested by Linus Torvalds in 1996. The name Tux is derived from (T) orvalds (U) ni (X). Linux Logo Linux Flavors

33. Resize window: Open Window that you want to resize (Ex. My Computer window) Click on Restore Button Place Mouse pointer on either of the border of window Press & Hold left mouse button, Move mouse

34. Diagram of Typical Window

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