1 Introduction to OS.ppt
- 2. Text Books Silberschatz, Galvin, and Gagne, “Operating System Concepts with Java,” Reference Books 1) William Stallings, “Operating Systems: Internal and Design Principles,” 5th Edition. Prentice-Hall, Inc. 2005. ISBN: 9780131479548 2) Andrew S. Tanenbaum and Albert S Woodhull, “Operating Systems Design and Implementation,” 3rd Edition. Prentice Hall, 2006. ISBN: 9780131429383. Reference Web Sites http://www.tutorialspoint.com/operating_system
- 3. A computer system consists of – hardware – system programs – application programs Introduction
- 5. An operating system is the interface between the user and the hardware. Operating System
- 6. Operating System Generations • The First Generation ( 1945 - 1955 ): Vacuum Tubes and Plugboards • The Second Generation ( 1955 - 1965 ): Transistors and Batch Systems • The Third Generation ( 1965 - 1980 ): Integrated Circuits and Multiprogramming • The Fourth Generation ( 1980 - Present ): Personal Computers
- 7. First generation (1940s-1950s) • It was the era of vacuum tubes, plug boards and punched cards. • Programmer used to interact with the machine directly through punched cards and used to write the programs in machine language • All the tasks for executing a program would be performed by the programmer only • There was no help like PL, linker, loader etc. • Obviously, there was no operating system
- 8. Second Generation (1950s-1960s) • Transistors based technology, mainframe computers, line printers, magnetic tapes, assemblers, linkers, loaders, compilers, FORTRAN, COBOL • Steps: loading the compiler tape of the required compiler Reading from card reader Running the compiler Unloading the compiler Loading the assembler tape Running the assembler Unloading the assembler tape Loading the object program Running the object program
- 9. • Problems and development of OS Set up delay problem due to loading and unloading of tapes in earlier computer system CPU was idle Jobs of users prepared with same PL were batched together Automated Job Sequencing ( turning point) Resident Monitor ( had to be in memory forever) Problem in Batch Systems I/O devices were electromechanical , on other hand CPU was electronic device Mismatch between the speed of CPU and I/O devices Offline operation with magnetic tapes Tapes were sequential access devices
- 10. Third Generation (1960s-1980s) • Problem in 2G: Tapes were sequential access devices • Need to carry separate tape for input and output as their storage capacity was low • Magnetic disk came into existence, as disks were random access devices and of higher storage capacity • IC based technology, Minicomputer
- 11. Problems and Development of OSs • Hard disks came into existence • Multi-programming • Multi-programmed batch systems • Spooling( Simultaneous Peripheral Operation Online) • Lack of user-programmer interaction with their jobs in multi-programmed batch systems • Time-sharing multi-user systems • CTSS (Compatible Time Sharing System) • MULTICS (Multiplexed information and Computing Service) • UNICS (Uniplexed Information and Computing Service) • UNIX • UNIX written in C
- 12. Fourth Generation (1980s-Present) • LSI and VLSI based technology • Microcomputer (later named as PCs) • Intel 8080 was the first Microprocessor for PC
- 13. Problems and Development of OSs • Gary kildall in Intel designed an OS called CP/M (control program for micro computers) for PCs • MS-DOS • Multiuser facility were not there in DOS • XENIX • OS/2 • No user friendliness and convenience due to command driven and complex file systems • Apple Macintosh • Windows • Multi-tasking • Multi- threading • UNIX developers lacking GUI ….X Windows, Motif • Network Operating Systems • Distributed Operating Systems
- 14. Four Components of a Computer System
- 15. Computer System Components • Hardware – provides basic computing resources. (CPU, memory, I/O devices). • Operating system – controls and coordinates the use of the hardware among the various application programs for the various users.
- 16. • Applications programs – define the ways in which the system resources are used to solve the computing problems of the users (compilers, database systems, video games, business programs). • Users (people, machines, other computers).
- 19. Operating System: Definitions OS simplifies and manages the complexity of running application programs efficiently. So, we can define: • OS as an extended machine – Hides the messy details which must be performed – Presents user with a virtual machine, easier to use • OS as resource manager – Coordination and control of limited resources such as memory, disk, network, etc – Deal with resource conflicts – Deal with resource fairness – Make access efficient as possible
- 20. • OS is a control program – Controls execution of programs to prevent errors and improper use of the computer – It is specially concerned with the operation and control of I/O devices. • OS as a Government – Like a government, it performs no useful function by itself. – It simply provides an environment within which other programs can do useful work. Operating System: Definitions
- 21. What does an Operating System Do? • Objectives of an OS – Convenience • An operating system makes a computer more convenient to use. – Efficiency • An operating system allows the computer system resources to be used in an efficient manner. – Ability to Evolve • Should permit effective development, testing, and introduction of new system features and functions without interfering with service.
- 22. Types of Operating System • Batch Processing systems • Multi-programming systems • Multi-user Time sharing systems • Multi-tasking systems • Network Operating Systems • Multi- Processor Operating Systems • Distributed Operating Systems
- 23. Batch Operating Systems • Were developed as a result of more set-up time for execution of different types of user programs • Can be used for user jobs which do not require user intervention • Main advantage of batch processing is to increase the CPU utilization • It is not meant for a quick response to the users, but it is still used to quantify the user service turnaround time • The time since the job was submitted to the system to the time when the user gets the result back
- 25. Multi- programming systems • Multi programming means to place several programs or jobs in main memory instead of a single program Two types of instruction in a program : • CPU bound and I/O bound • CPU has an instruction for processing or computation • There is a request to an I/P or O/P device to read or write
- 29. Benefits of Multi-programming • Less execution time : spooling and switching between the jobs frequently by CPU • Increased utilization of memory : instead of storing a single program in memory, more than one program is stored thereby utilizing the main memory • Increased throughput Throughput= No of jobs completed per unit time Throughput is increased if degree of multi programming is increased
- 30. Multi-User Time sharing system • Batch and multi- programmed batch systems do not provide immediate response to the user • If one user submits his/her job, he/she has to wait for the execution of all the jobs in the batch and then get the output • Waiting time of a user is more and he/she is not in direct touch with his/her job • Problem is due to non-interactive input and output devices
- 34. Benefits • Multiuser facility: multiple users connected to a single system where each user presents the job to the system and gets the response • Improved response time : user now is in direct touch of his job and due to easy interface, he views everything regarding his job • Improved Debugging and Productivity : user can view his mistake, debugging of programs is easy. Quickly modifies program and run again, thereby increasing productivity also
- 35. Multi tasking systems Time sharing and multi tasking are also used interchangeably Multi user and multi tasking are different terms, and time sharing is the scheduling technique in both of them
- 36. Multi-programming : place more than one job/ program/task in the main memory Multiuser System: place more than one job/ program/task in the main memory of the main computer system. Here jobs come from the different users who are connected through terminals to the main computer. Jobs are scheduled by time sharing technique
- 37. Multi tasking systems : place more than one job/program/task in the main memory of the system. The jobs here are of a single user working on the system. Jobs are scheduled by time sharing technique
- 38. Network Operating System • This system coordinates the activities on a network system • In a network each node has its own local operating system • User is able to connect to another machine and perform many operations • User must be aware of the location of the network node where he/she wants to connect • When a user wants to remote log onto a system, wants to transfer a file etc. on a network system
- 39. • User may perform both local and non local operations • Non-local operations, the role of network operating system starts • NOS may be considered as another layer of software on the operating system on a local machine
- 40. Distributed Operating system • Works in a WAN • Each node in a distributed system is a complete computer having full set of peripherals including OS • Main motive is resource sharing • Users are not aware where their processes are being sent and executed
- 42. Tasks to be met by DOS Three types of migration • Data migration transferring data from one site to another site • Computation migration transferring the computation on a particular node • Process migration the process or its sub processes may also need to be transferred to some other nodes due to some reasons like load balancing, computation speed etc
- 43. Real time systems • Time sharing system drawback, if more load on system, response time was further increased with increase in load • Some systems cannot bear delay. • Used to handle time bound responses to the applications • Applicable to systems which require time bound response, i.e. for real time processing systems ( immediate or within a fixed time frame) •
- 45. • Examples : • Defense applications like guided missile systems, air traffic control systems • Two types 1.Hard real time system : have hard deadlines and must be met 2.Soft real time system : missing of some deadline is acceptable. E.g. digital audio, multimedia systems, virtual reality Delay here must be bounded and predictable and should not be infinite
- 46. Embedded systems • Specialized systems with size, memory and power restrictions • Used in consumer electronic items, mobile phones, smart cards etc. • Embedded systems also have OS but they are not generalized ones • User uses these devices without any awareness of operating system
- 47. • Embedded Oss are there to perform all the basic functionalities like initialization, task management, memory management etc. • There are OS, but not in the same structure as in general purpose computer systems
- 48. Oss generic components • Hardware • Kernel • Shell • System and application programs • user
- 49. • Kernel : A kernel is the central part of an operating system. It manages the tasks of the computer and the hardware - most notably memory and CPU time. • Command interpreter or shell : A program which reads and interprets the control statements and passes the signals to operating system
- 50. Kernel types • Monolithic • Microkernel
- 51. MONOLITHIC ARCHITECTURE Therefore, all the functionalities were added in the kernel only. The advantage of this type of architecture was that intercommunication between the modules of the OS was efficient, as all the modules were in the kernel together
- 53. MONOLITHIC ARCHITECTURE • Due to all functionalities merged in a single layer, it was difficult to do modifications in a module. • debugging in the modules of the OS became a difficult job. • Another disadvantage of this architecture was that there was no protection. • Monolithic systems were not suitable for multi- programming/multi-tasking environments due to unprotected behavior of the system. The DOS, initial architecture of UNIX, and Linux are some examples of monolithic structures.
- 54. MICROKERNEL ARCHITECTURE • To remove heavy functionalities from the kernel, it was thought that some essential functionality will remain inside the kernel known as essential core of the OS code. • The kernel, consisting of essential core, is called microkernel. • The components of the essential core may be process management, inter-process communication, low-level memory management, and so on. • The other OS modules, which were considered as non-essential, were moved up in the user space. In this way, microkernel was designed to manage the large-size kernel by dividing it into two parts: kernel space code and user space code.
- 55. MICROKERNEL ARCHITECTURE • Developers have discussed features to be included inside the kernel and features to be incorporated in the user space. • The modules implemented outside the kernel in user space are called server processes. • The application programs of the user (client programs) communicate with the server process. The server processes provide various services like file system management, process scheduling, device management, networking, and so on. • The communication between the client applications and server processes is through the message-passing communication method, called as Inter-process Communication (IPC), also known as client- server architecture of OSs.