Computer Operating System - Lecture 3: Operating - System structures - Nguyen Thanh Son

Nội dung text: Computer Operating System - Lecture 3: Operating - System structures - Nguyen Thanh Son

1. Chapter’s Content  System Components  Operating System Services  System Calls  System Programs  System Structure  Virtual Machines  System Design and Implementation  System Generation BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 2
2. Process Management  A process is a program in execution. A process needs certain resources, including CPU time, memory, files, and I/O devices, to accomplish its task.  The operating system is responsible for the following activities in connection with process management.  Process creation and deletion.  process suspension and resumption.  Provision of mechanisms for:  process synchronization BK  process communication TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 4
3. File Management  A file is a collection of related information defined by its creator. Commonly, files represent programs (both source and object forms) and data.  The operating system is responsible for the following activities in connections with file management:  File creation and deletion.  Directory creation and deletion.  Support of primitives for manipulating files and directories.  Mapping files onto secondary storage.  File backup on stable (nonvolatile) storage media. BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 6
4. Secondary-Storage Management  Since main memory (primary storage) is volatile and too small to accommodate all data and programs permanently, the computer system must provide secondary storage to back up main memory.  Most modern computer systems use disks as the principle on-line storage medium, for both programs and data.  The operating system is responsible for the following activities in connection with disk management:  Free space management  Storage allocation BK  Disk scheduling TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 8
5. Protection System  Protection refers to a mechanism for controlling access by programs, processes, or users to both system and user resources.  The protection mechanism must:  distinguish between authorized and unauthorized usage.  specify the controls to be imposed.  provide a means of enforcement. BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 10
6. Command-Interpreter System (Cont.)  The program that reads and interprets control statements is called variously:  command-line interpreter  shell (in UNIX) Its function is to get and execute the next command statement. BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 12
7. Additional Operating System Functions Additional functions exist not for helping the user, but rather for ensuring efficient system operations. • Resource allocation – allocating resources to multiple users or multiple jobs running at the same time. • Accounting – keep track of and record which users use how much and what kinds of computer resources for account billing or for accumulating usage statistics. • Protection – ensuring that all access to system resources is controlled. BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 14
8. Passing of Parameters As A Table BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 16
9. MS-DOS Execution At System Start-up Running a Program BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 18
10. Communication Models  Communication may take place using either message passing or shared memory. Msg Passing Shared Memory BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 20
11. MS-DOS System Structure  MS-DOS – written to provide the most functionality in the least space  not divided into modules  Although MS-DOS has some structure, its interfaces and levels of functionality are not well separated BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 22
12. UNIX System Structure  UNIX – limited by hardware functionality, the original UNIX operating system had limited structuring. The UNIX OS consists of two separable parts.  Systems programs  The kernel  Consists of everything below the system-call interface and above the physical hardware  Provides the file system, CPU scheduling, memory management, and other operating-system functions; a large number of functions for one level. BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 24
13. Layered Approach  The operating system is divided into a number of layers (levels), each built on top of lower layers. The bottom layer (layer 0), is the hardware; the highest (layer N) is the user interface.  With modularity, layers are selected such that each uses functions (operations) and services of only lower-level layers. BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 26
14. OS/2 Layer Structure BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 28
15. Windows NT Client-Server Structure BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 30
16. Virtual Machines (Cont.)  The resources of the physical computer are shared to create the virtual machines.  CPU scheduling can create the appearance that users have their own processor.  Spooling and a file system can provide virtual card readers and virtual line printers.  A normal user time-sharing terminal serves as the virtual machine operator’s console. BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 32
17. Advantages/Disadvantages of Virtual Machines  The virtual-machine concept provides complete protection of system resources since each virtual machine is isolated from all other virtual machines. This isolation, however, permits no direct sharing of resources.  A virtual-machine system is a perfect vehicle for operating-systems research and development. System development is done on the virtual machine, instead of on a physical machine and so does not disrupt normal system operation.  The virtual machine concept is difficult to implement due to the effort required to provide an exact duplicate to the BK underlying machine. TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 34
18. Java Virtual Machine BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 36
19. Mechanisms and Policies  Mechanisms determine how to do something, policies decide what will be done.  The separation of policy from mechanism is a very important principle, it allows maximum flexibility if policy decisions are to be changed later. BK TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 38
20. System Generation (SYSGEN)  Operating systems are designed to run on any of a class of machines; the system must be configured for each specific computer site.  SYSGEN program obtains information concerning the specific configuration of the hardware system.  Booting – starting a computer by loading the kernel.  Bootstrap program – code stored in ROM that is able to locate the kernel, load it into memory, BK and start its execution. TP.HCM 07-Feb-17 Faculty of Computer Science & Engineering 40