An Introduction to Operating Systems
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An operating system manages all hardware and software on a computer system. It has several essential managers like memory, processor, device, and file managers. A networked operating system also includes a network manager. Operating systems are classified as batch, interactive, real-time, hybrid, or embedded based on response time and data entry. Modern operating systems use object-oriented design and multiprocessing for improved performance and flexibility.
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An Introduction to Operating Systems
- 1. Understanding Operating Systems I think there is a world market for maybe five computers. Thomas J. Watson (18741956; chairman of IBM 19491956)
- 2. What is an Operating System? Operating System: Part of the computing system that manages all of the hardware and software Controls every file, every device, every section of main memory, and every nanosecond of processing time Controls who can use the system and how Computer system consists of: Software (programs) Hardware (the physical machine and its electronic components)
- 3. Operating System Software Essential managers of an operating system: Memory Manager Processor Manager Device Manager File Manager Each manager both works closely with the other managers and performs its unique role User Command Interface is unique to each operating system
- 4. Operating System Software (continued) Figure 1.1: Model of a non - networked operating system
- 5. Operating System Software (continued) Each subsystem manager must perform the following tasks: Monitor its resources continuously Enforce the policies that determine who gets what, when, and how much Allocate the resource when its appropriate Deallocate the resource when appropriate
- 6. Operating System Software (continued) Figure 1.2: Subsystems managers at the base of a pyramid
- 7. Operating System Software (continued) Memory Manager: In charge of main memory (RAM) Responsibilities include: Preserves the space in main memory occupied by the operating system Checks the validity of each request for memory space Sets up a table to keep track of who is using which section of memory in a multiuser environment Deallocates memory when the time comes to reclaim the memory
- 8. Operating System Software (continued) Processor Manager decides how to allocate the central processing unit (CPU) Processor Manager has two levels of responsibility: To handle jobs as they enter the system Handled by Job Scheduler To manage each process within those jobs Handled by Process Scheduler
- 9. Operating System Software (continued) Device Manager monitors every device, channel, and control unit Responsibilities include: Chooses the most efficient way to allocate all of the systems devices, printers, terminals, disk drives, based on a scheduling policy Makes the allocation, starts its operation Deallocates the device
- 10. Operating System Software (continued) File Manager keeps track of every file in the system including data files, assemblers, compilers, and application programs Responsibilities include: Enforces restrictions on who has access to which files by using predetermined access Controls what users are allowed to do with files once they access them Allocates the resource by opening the file and deallocates it by closing the file
- 11. Operating System Software (continued) Operating systems with networking capability have a fifth essential manager called the Network Manager Network Manager provides a convenient way for users to share resources while controlling users access to them. The resources include: Hardware (such as CPUs, memory areas, printers, tape drives, modems, and disk drives) Software (such as compilers, application programs, and data files)
- 12. Operating System Software (continued) Figure 1.3: Model of a networked operating system
- 13. Machine Hardware Essential hardware components include: Memory chips Input/output devices Storage devices Central processing unit (CPU)
- 14. Machine Hardware (continued) Figure 1.4: Computer system hardware configuration
- 15. Machine Hardware (continued) Table 1.1: Different platforms and operating systems
- 16. Types of Operating Systems (continued) Operating systems for computers fall into following five categories : Batch Interactive Real-time Hybrid Embedded Distinguished by response time and how data is entered into the system
- 17. Types of Operating Systems (continued) Batch Systems: Relied on punched cards or tape for input in past Efficiency of the system was measured in throughput Interactive Systems: Gives a faster turnaround than batch systems but are slower than the real-time systems Introduced for users who needed fast turnaround when debugging their programs Operating system required the development of time sharing software
- 18. Types of Operating Systems (continued) Real-time systems: Fastest and used in time-critical environments Real-time systems are used for: Space flights, airport traffic control, high-speed aircraft Industrial processes Sophisticated medical equipment Distribution of electricity Telephone switching A real-time system must be 100 percent responsive, 100 percent of the time
- 19. Types of Operating Systems (continued) Hybrid Systems: Combination of batch and interactive Accepts and runs batch programs in the background when the interactive load is light Embedded Systems: Computers placed inside other products to add features and capabilities Operating systems with small kernel and flexible functions capabilities will have potential for embedded system
- 20. Current Operating Systems Primary design features of current operating systems are based on providing support for Multimedia applications Internet and Web access Client/server computing Computer systems are required to have Increased CPU speed High-speed network attachments Increased number and variety of storage devices
- 21. System Architecture Improvements in system architecture Use of object-oriented design Possible to modify and customize pieces of an operating system without disrupting the integrity of the remainder of the system Makes software development groups more productive Reorganization of the operating systems kernel Limited to a few essential functions
- 22. System Architecture (continued) Figure 1.10: (a) Early operating systems; (b) & (c) Modern object-oriented systems
- 23. Threads Thread: A portion of a program that can run independently of other portions The heavyweight process which owns the resources becomes a more passive element Thread becomes the element that uses the CPU and is scheduled for execution Swapping threads is less time consuming than swapping processes Multithreaded applications programs can have several threads running at one time with the same or different priorities
- 24. Multiprocessing Configurations Symmetric multiprocessing: Allows for several CPUs to process multiple jobs at the same time CPUs are independent of one another, but each has access to the operating system Asymmetric multiprocessing: Some operating systems functions are assigned to subordinate processors, which take their instructions from the main CPU
- 25. Multiprocessing Configurations (continued) Figure 1.11: Symmetric multiprocessing system with five processors
- 26. Multiprocessing Configurations (continued) Network PCs gave impetus to the concept of distributed processing Processors are placed at remote locations and are connected to each other via telecom devices Different from symmetric multiprocessing systems as they do not share memory Computations can be dispersed among several processors Overall capability of the computer system is maximized
- 27. Summary Operating System manages all of the hardware and software of a computer system Each manager of an OS both works closely with the other managers and performs its unique role Operating systems with networking capability have Network Manager Essential hardware components include memory chips , I/O, storage devices and CPU Until mid-1970s, computers were classified by capacity and price
- 28. Summary (continued) Computing power has been rising exponentiallyMoores Law Dramatic changes in physical size, cost, and memory capacity with time Networking has become an integral part of modern computer systems Delivering information to a mobile society, creating a strong market for handheld devices Operating systems fall into following five categories: b atch , i nteractive , r eal-time , hybrid and embedded
- 29. Summary (continued) U se of object-oriented design improved the system architecture Symmetric multiprocessing allows for several CPUs to process multiple jobs at the same time Network PCs gave impetus to the concept of distributed processing