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Bài giảng Hệ điều hành nâng cao - Chapter 2: Operating - System Structures

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Bài giảng Hệ điều hành nâng cao - Chapter 2: Operating - System Structures

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  1. Chapter 2: Operating-System Structures Operating System Concepts – 8th Edition Operating System Concepts – 8th Edition 2.1 Silberschatz, Galvin and Gagne ©2009
  2. Chapter 2: Operating-System Structures s Operating System Services s User Operating System Interface s System Calls s Types of System Calls s System Programs s Operating System Design and Implementation s Operating System Structure s Virtual Machines s Operating System Debugging s Operating System Generation s System Boot Operating System Concepts – 8th Edition 2.2 Silberschatz, Galvin and Gagne ©2009
  3. Objectives s To describe the services an operating system provides to users, processes, and other systems s To discuss the various ways of structuring an operating system s To explain how operating systems are installed and customized and how they boot Operating System Concepts – 8th Edition 2.3 Silberschatz, Galvin and Gagne ©2009
  4. Operating System Services s Operating systems provide an environment for execution of programs and services to programs and users s One set of operating-system services provides functions that are helpful to the user: q User interface - Almost all operating systems have a user interface (UI). 4 Varies between Command-Line (CLI), Graphics User Interface (GUI), Batch q Program execution - The system must be able to load a program into memory and to run that program, end execution, either normally or abnormally (indicating error) q I/O operations - A running program may require I/O, which may involve a file or an I/O device q File-system manipulation - The file system is of particular interest. Programs need to read and write files and directories, create and delete them, search them, list file Information, permission management. Operating System Concepts – 8th Edition 2.4 Silberschatz, Galvin and Gagne ©2009
  5. Operating System Services (Cont.) q Communications – Processes may exchange information, on the same computer or between computers over a network 4 Communications may be via shared memory or through message passing (packets moved by the OS) q Error detection – OS needs to be constantly aware of possible errors 4 May occur in the CPU and memory hardware, in I/O devices, in user program 4 For each type of error, OS should take the appropriate action to ensure correct and consistent computing 4 Debugging facilities can greatly enhance the user’s and programmer’s abilities to efficiently use the system Operating System Concepts – 8th Edition 2.5 Silberschatz, Galvin and Gagne ©2009
  6. Operating System Services (Cont.) s Another set of OS functions exists for ensuring the efficient operation of the system itself via resource sharing q Resource allocation - When multiple users or multiple jobs running concurrently, resources must be allocated to each of them 4 Many types of resources - Some (such as CPU cycles, main memory, and file storage) may have special allocation code, others (such as I/O devices) may have general request and release code q Accounting - To keep track of which users use how much and what kinds of computer resources q Protection and security - The owners of information stored in a multiuser or networked computer system may want to control use of that information, concurrent processes should not interfere with each other 4 Protection involves ensuring that all access to system resources is controlled 4 Security of the system from outsiders requires user authentication, extends to defending external I/O devices from invalid access attempts 4 If a system is to be protected and secure, precautions must be instituted throughout it. A chain is only as strong as its weakest link. Operating System Concepts – 8th Edition 2.6 Silberschatz, Galvin and Gagne ©2009
  7. A View of Operating System Services Operating System Concepts – 8th Edition 2.7 Silberschatz, Galvin and Gagne ©2009
  8. User Operating System Interface - CLI s Command Line Interface (CLI) or command interpreter allows direct command entry 4 Sometimes implemented in kernel, sometimes by systems program 4 Sometimes multiple flavors implemented – shells 4 Primarily fetches a command from user and executes it – Sometimes commands built-in, sometimes just names of programs » If the latter, adding new features doesn’t require shell modification Operating System Concepts – 8th Edition 2.8 Silberschatz, Galvin and Gagne ©2009
  9. User Operating System Interface - GUI s User-friendly desktop metaphor interface q Usually mouse, keyboard, and monitor q Icons represent files, programs, actions, etc q Various mouse buttons over objects in the interface cause various actions (provide information, options, execute function, open directory (known as a folder) q Invented at Xerox PARC s Many systems now include both CLI and GUI interfaces q Microsoft Windows is GUI with CLI “command” shell q Apple Mac OS X as “Aqua” GUI interface with UNIX kernel underneath and shells available q Solaris is CLI with optional GUI interfaces (Java Desktop, KDE) Operating System Concepts – 8th Edition 2.9 Silberschatz, Galvin and Gagne ©2009
  10. Bourne Shell Command Interpreter Operating System Concepts – 8th Edition 2.10 Silberschatz, Galvin and Gagne ©2009
  11. The Mac OS X GUI Operating System Concepts – 8th Edition 2.11 Silberschatz, Galvin and Gagne ©2009
  12. System Calls s Programming interface to the services provided by the OS s Typically written in a high-level language (C or C++) s Mostly accessed by programs via a high-level Application Program Interface (API) rather than direct system call use s Three most common APIs are Win32 API for Windows, POSIX API for POSIX-based systems (including virtually all versions of UNIX, Linux, and Mac OS X), and Java API for the Java virtual machine (JVM) s Why use APIs rather than system calls? (Note that the system-call names used throughout this text are generic) Operating System Concepts – 8th Edition 2.12 Silberschatz, Galvin and Gagne ©2009
  13. Example of System Calls s System call sequence to copy the contents of one file to another file Operating System Concepts – 8th Edition 2.13 Silberschatz, Galvin and Gagne ©2009
  14. Example of Standard API s Consider the ReadFile() function in the s Win32 API—a function for reading from a file s A description of the parameters passed to ReadFile() q HANDLE file—the file to be read q LPVOID buffer—a buffer where the data will be read into and written from q DWORD bytesToRead—the number of bytes to be read into the buffer q LPDWORD bytesRead—the number of bytes read during the last read q LPOVERLAPPED ovl—indicates if overlapped I/O is being used Operating System Concepts – 8th Edition 2.14 Silberschatz, Galvin and Gagne ©2009
  15. System Call Implementation s Typically, a number associated with each system call q System-call interface maintains a table indexed according to these numbers s The system call interface invokes intended system call in OS kernel and returns status of the system call and any return values s The caller need know nothing about how the system call is implemented q Just needs to obey API and understand what OS will do as a result call q Most details of OS interface hidden from programmer by API 4 Managed by run-time support library (set of functions built into libraries included with compiler) Operating System Concepts – 8th Edition 2.15 Silberschatz, Galvin and Gagne ©2009
  16. API – System Call – OS Relationship Operating System Concepts – 8th Edition 2.16 Silberschatz, Galvin and Gagne ©2009
  17. Standard C Library Example s C program invoking printf() library call, which calls write() system call Operating System Concepts – 8th Edition 2.17 Silberschatz, Galvin and Gagne ©2009
  18. System Call Parameter Passing s Often, more information is required than simply identity of desired system call q Exact type and amount of information vary according to OS and call s Three general methods used to pass parameters to the OS q Simplest: pass the parameters in registers 4 In some cases, may be more parameters than registers q Parameters stored in a block, or table, in memory, and address of block passed as a parameter in a register 4 This approach taken by Linux and Solaris q Parameters placed, or pushed, onto the stack by the program and popped off the stack by the operating system q Block and stack methods do not limit the number or length of parameters being passed Operating System Concepts – 8th Edition 2.18 Silberschatz, Galvin and Gagne ©2009
  19. Parameter Passing via Table Operating System Concepts – 8th Edition 2.19 Silberschatz, Galvin and Gagne ©2009
  20. Types of System Calls s Process control q end, abort q load, execute q create process, terminate process q get process attributes, set process attributes q wait for time q wait event, signal event q allocate and free memory s File management q create file, delete file q open, close file q read, write, reposition q get and set file attributes Operating System Concepts – 8th Edition 2.20 Silberschatz, Galvin and Gagne ©2009
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