Operating System 2018 Unit – I Operating System 1. Introduction A computer system has many resources (hardware and software), which may be require to complete a task. The commonly required resources are input/output devices, memory, file storage space, CPU etc. The operating system acts as a manager of the above resources and allocates them to specific programs and users, whenever necessary to perform a particular task. Therefore operating system is the resource manager i.e. it can manage the resource of a computer system internally. The resources are processor, memory, files, and I/O devices. In simple terms, an operating system is the interface between the user and the machine. An operating system (OS), in its most general sense, is software that allows a user to run other applications on a computing device. While it is possible for a software application to interface directly with hardware, the vast majority of applications are written for an OS, which allows them to take advantage of common libraries and not worry about specific hardware details. The operating system manages a computer's hardware resources, including: Input devices such as a keyboard and mouse Output devices such as display monitors, printers and scanners Network devices such as modems, routers and network connections Storage devices such as internal and external drives The OS also provides services to facilitate the efficient execution and management of, and memory allocations for, any additional installed software application programs. Some operating systems were developed in the 1950s, when computers could only execute one program at a time. Later in the decade, computers included many software programs, sometimes called libraries, which were linked together to create the beginning of today's operating systems. The OS consists of many components and features. Which features are defined as part of the OS vary with each OS. However, the three most easily defined components are: Kernel: This provides basic-level control over all of the computer hardware devices. Main roles include reading data from memory and writing data to memory, processing A.Tamilmani, MIT, MCA, PGDCA, MPhil, Asst.Prof in IT, BDUCCL Kumulur Page 1 Operating System 2018 execution orders, determining how data is received and sent by devices such as the monitor, keyboard and mouse, and determining how to interpret data received from networks. User Interface: This component allows interaction with the user, which may occur through graphical icons and a desktop or through a command line. Application Programming Interfaces: This component allows application developers to write modular code. Examples for OSs include Android, iOS, Mac OS X, Microsoft Windows and Linux. 1.1. Two Views of Operating System 1. User's View 2. System View Operating System: User View The user view of the computer refers to the interface being used. Such systems are designed for one user to monopolize its resources, to maximize the work that the user is performing. In these cases, the operating system is designed mostly for ease of use, with some attention paid to performance, and none paid to resource utilization. Operating System: System View Operating system can be viewed as a resource allocator also. A computer system consists of many resources like - hardware and software - that must be managed efficiently. The operating system acts as the manager of the resources, decides between conflicting requests, controls execution of programs etc. 1.2. Operating System Management Tasks 1. Processor management which involves putting the tasks into order and pairing them into manageable size before they go to the CPU. 2. Memory management which coordinates data to and from RAM (random-access memory) and determines the necessity for virtual memory. 3. Device management which provides interface between connected devices. 4. Storage management which directs permanent data storage. 5. Application which allows standard communication between software and your computer. 6. User interface which allows you to communicate with your computer. 1.3. Basic functions of operating systems: 1. Memory Management It manages the allocation of memory of system for different processes. It manages both the primary memory and secondary memory. 2. Processor Management It manages all the running processes in computer system. A process is simply a program that is run by a user on computer system. 3. Security Management A.Tamilmani, MIT, MCA, PGDCA, MPhil, Asst.Prof in IT, BDUCCL Kumulur Page 2 Operating System 2018 It ensures the security of computer system from the various threats and viruses attacks. An operating system uses various techniques such as authentication, authorization, cryptography etc. for ensuring security of compute system. 4. Device Management This function of operating system is used to manage different devices that are connected with the computer system. An operating system interact with hardware device through specified device drivers. 5. File Management An operating system manages the files and directories of computer system. A file can be defined as a collection of information or data that is store in the memory of computer system. An operating system allow us to create, delete, save, edit files in a computer system. 1.4.Types of operating system: Many different types of operating systems are involved till date. The operating systems are improved in terms of their capabilities. The modern days operating systems allows multiple user to carry out multiple tasks simultaneously. Based on their capabilities and the types of application supported, the operating systems can be divided into following six major categories. 1. Batch processing operating systems 2. Multi user operating systems 3. Multitasking operating systems 4. Real time operating systems 5. Multi processors operating systems 6. Embedded operating systems Batch processing operating system The batch processing operating system is capable of executing one job at a time. In batch processing operating system the jobs are combined in form of batch and then these batches are given to system as an input data. The job in batches are processed on first com first serve basis. After execution of one job operating system fetches another job from input data. There is no need of human interaction before fetching the next job after completion of any job. A.Tamilmani, MIT, MCA, PGDCA, MPhil, Asst.Prof in IT, BDUCCL Kumulur Page 3 Operating System 2018 Multi user operating system The multi user operating system uses to use a system by multiple users. In other word multi user operating system allows a number of users to work simultaneously on a single computer system. These types of operating systems are specially designed for the multi user system. Examples of multi user operating systems includes Unix, Linux, Windows 2000 and VM - 386. Multitasking operating system The multitasking operating system allow a user to give multitask at a same time on a single computer system multitasking operating system are also known as multiprocessing operating system and multiprogramming operating system. The first multitasking operating system is created in 1960s. The number of tasks processed simultaneously by this operating system is depending upon speed of CPU, the capacity of memory and size of programs. Examples of multitasking operating systems are Linux, Unix, windows 2000, windows XP, windows 10. Real time operating system The real time operating system is similar as multitasking operating system. However, these operating systems are specially designed to handle real time applications. Real time applications are those applications which have to execute within a specific period of time. Therefore, time is major constraint for these applications. The different examples of real time applications are robots, machine learning etc. There are mainly two types of real time operating system. Hard real time operating system and soft real time operating system. Examples of real time operating systems are MTOS, Lynx, RTX etc. Multiprocessor operating system The multiprocessor operating system allows the computer system to use more than one CPU in a single system for executing more than one or multiple processes at a time. A computer system having multiple CPU process faster than a system which contains a single CPU. Examples of multiprocessor operating systems are Linux, Unix, windows 2000 etc. Embedded operating system The embedded operating system is similar to real time operating system. This operating system is installed on an embedded computer system which is primary used to perform computational tasks in electronic devices. A.Tamilmani, MIT, MCA, PGDCA, MPhil, Asst.Prof in IT, BDUCCL Kumulur Page 4 Operating System 2018 1.5. History of Machine Hardware Computer was referred as the machine which can carry the task of computation form the end of the 19th century. However now it is not just a calculation machine, it has diversified applications and it has even revolutionized the industry. If we make a deep analysis regarding the history of the computer we have to go back in 16th century. However the true progress in this field started in early nineteenth century. Early Digital Computers If we briefly analyze the history of computer hardware, we can see innumerable changes in the hardware overtime. Zues was introduced in Germany in 1941; it uses binary coding for its operation. It involves the lector mechanical computing mechanism. Then after one year in 1942 Attansoff Berry computer came to surface with electric binary computing mechanism. Its origin was USA. Colluses Mark was a UK based technology and it emerged in 1944. It was also based on binary numeral principle. In the same year in Harvard, Harvard Mark IBM ASCC was introduced. ENIAC was introduced in 1946; it had its origin from UK. The modified version of ENIAC was introduced in 1948, as in 1949 EDSAC, Manchester Mark and CSIRAC came forward. The early computers and the associated hardware were really expensive and heavy. For example first portable computer weighed about 25kg. History of Associated Hardware With the development in computers, the hardware of the Pc was also improved.