lecture 1 (Introduction to Operating System.)

10 de Mar de 2020

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lecture 1 (Introduction to Operating System.)

  1. Unit 1 –part 1 Introduction
  2. Course Administration Text & Reference Books: Operating System Concepts Eighth Edition Abraham Silberschatz, the Peter Gaivin, Greg Gagne Abraham Silberschatz, the Peter Gaivin, Greg Gagne, Applied Operating System Concepts (practical concept of the operating system)., John Wiley & Sons, Inc.2000 (Beijing: Higher Education Press .2001,5)
  3. Basic components of a computer system: place of OS • A 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 –solve the problems of the users: use system resources • Word processors, compilers, web browsers, database systems, video games • Users • People, machines, other computers •3
  4. What is an Operating System • A program that acts as an intermediary between a users/applications and the computer hardware • An operating system (OS) is a collection of software that manages computer hardware resources and provides common services for computer programs. The operating system is a vital component of the system software in a computer system. • An Operating System (OS) is an interface between a computer user and computer hardware. An operating system is a 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 Linux Operating System, Windows Operating System, VMS, OS/400, AIX, z/OS, etc.
  5. 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.
  6. Functions of an operating System
  7. Functions of an operating System • Process management:- Process management helps OS to create and delete processes. It also provides mechanisms for synchronization and communication among processes. • 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. • 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.
  8. • 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. • 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 and acting system resources to process that commands. • 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. Functions of an operating System
  9. Functions of an operating System • Job accounting: Keeping track of time & resource used by various job and users. • Communication management: Coordination and assignment of compilers, interpreters, and another software resource of the various users of the computer systems.
  10. Types of Operating system • Batch Operating System • Multitasking/Time Sharing OS • Multiprocessing OS • Real Time OS • Distributed OS • Network OS • Mobile OS
  11. Types of Operating system Batch Operating System Some computer processes are very lengthy and time-consuming. To speed the same process, a job with a similar type of needs are batched together and run as a group. The user of a batch operating system never directly interacts with the computer. In this type of OS, every user prepares his or her job on an offline device like a punch card and submit it to the computer operator. Multi-Tasking/Time-sharing Operating systems Time-sharing operating system enables people located at a different terminal(shell) to use a single computer system at the same time. The processor time (CPU) which is shared among multiple users is termed as time sharing. Real time OS A real time operating system time interval to process and respond to inputs is very small. Examples: Military Software Systems, Space Software Systems.
  12. Types of Operating system Distributed Operating System Distributed systems use many processors located in different machines to provide very fast computation to its users. Network Operating System Network Operating System runs on a server. It provides the capability to serve to manage data, user, groups, security, application, and other networking functions. Mobile OS Mobile operating systems are those OS which is especially that are designed to power smartphones, tablets, and wearables devices. Some most famous mobile operating systems are Android and iOS, but others include BlackBerry, Web, and watchOS.
  13. Difference between Firmware and Operating System Firmware Operating System Firmware is one kind of programming that is embedded on a chip in the device which controls that specific device. OS provides functionality over and above that which is provided by the firmware. Firmware is programs that been encoded by the manufacture of the IC or something and cannot be changed. OS is a program that can be installed by the user and can be changed. It is stored on non-volatile memory. OS is stored on the hard drive.
  14. The advantage of using Operating System • Allows you to hide details of hardware by creating an abstraction • Easy to use with a GUI • Offers an environment in which a user may execute programs/applications • The operating system must make sure that the computer system convenient to use • Operating System acts as an intermediary among applications and the hardware components • It provides the computer system resources with easy to use format • Acts as an intermediator between all hardware's and software's of the system
  15. Disadvantages of using Operating System • If any issue occurs in OS, you may lose all the contents which have been stored in your system • Operating system's software is quite expensive for small size organization which adds burden on them. Example Windows • It is never entirely secure as a threat can occur at any time
  16. Goals of an Operating System • Simplify the execution of user programs and make solving user problem easier. • Use Computer hardware efficiently • Allow sharing of hardware and software resources. • Make application software portable and versatile. • Provide isolation, security and protection among user problems. • Improve overall system reliability • Error confinement, fault tolerance, reconfiguration.
  17. A Multi-user operating system A Multi-user operating system is a computer operating system which allows multiple users to access the single system with one operating system on it. It is generally used on large mainframe computers. Example: Linux, Unix, Windows 2000, Ubuntu, Mac OS etc., In the multi-user operating system, different users connected at different terminals and we can access, these users through the network
  18. Features of the Multi-user Operating System Multi-tasking- Using multi-user operating system we can perform multiple tasks at a time, i.e. we can run more than one program at a time. Example: we can edit a word document while browsing the internet. Resource sharing- we can share different peripherals like printers, hard drives or we can share a file or data. For this, each user is given a small time slice of CPU time. Background processing- It means that when commands are not processed firstly, then they are executed in the background while another programs are interacting with the system in the real time.
  19. Operating System Structure An operating system is a construct that allows the user application programs to interact with the system hardware. Since the operating system is such a complex structure, it should be created with utmost care so it can be used and modified easily. An easy way to do this is to create the operating system in parts. Each of these parts should be well defined with clear inputs, outputs and functions.
  20. Simple Structure There are many operating systems that have a rather simple structure. These started as small systems and rapidly expanded much further than their scope. A common example of this is MS-DOS. It was designed simply for a niche amount for people. There was no indication that it would become so popular. It is better that operating systems have a modular structure, unlike MS-DOS. That would lead to greater control over the computer system and its various applications. The modular structure would also allow the programmers to hide information as required and implement internal routines as they see fit without changing the outer specifications.
  21. Simple Structure
  22. Layered Structure One way to achieve modularity in the operating system is the layered approach. In this, the bottom layer is the hardware and the topmost layer is the user interface. As seen from the image, each upper layer is built on the bottom layer. All the layers hide some structures, operations etc from their upper layers. One problem with the layered structure is that each layer needs to be carefully defined. This is necessary because the upper layers can only use the functionalities of the layers below them.
  23. Layered Structure
  24. The Operating System as a Resource Manager • Internally an Operating System acts as a manager of resources of the computer system such as processor, memory, files, and I/O device. • In this role, the operating system keeps track of the status of each resource, and decides who gets a resource, for how long and when. • In system that supports concurrent execution of program, the operating system resolves conflicting requests for resources in manner that preserves system integrity, and in doing so attempts to optimize the resulting performance.
  25. Operating System Definition • OS is the one program running all times on the computer. • Kernel: running all the time; having most of the functionality • Everything else: either a system program or an application program 25 system programs (Some application programs) OS CD kernel System programs: programs that are associated with the operating system + you can install other applications