* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Slide 1
Survey
Document related concepts
Berkeley Software Distribution wikipedia , lookup
Library (computing) wikipedia , lookup
Mobile operating system wikipedia , lookup
Plan 9 from Bell Labs wikipedia , lookup
Security-focused operating system wikipedia , lookup
Copland (operating system) wikipedia , lookup
Spring (operating system) wikipedia , lookup
Burroughs MCP wikipedia , lookup
Distributed operating system wikipedia , lookup
Process management (computing) wikipedia , lookup
Transcript
Chapter 1: Introduction Topics What is an operating system Computer System Components History of operating systems Operating system concepts Operating system structure Reference: Operating Systems Design and Implementation (2nd edition) by Andrew S. Tanenbaum and Albert S. Woodhull What is an Operating System(1) • A program that acts as an intermediary between a user of a computer and the computer hardware. • Operating system goals: – Execute user programs and make solving user problems easier. – Make the computer system convenient to use. • Use the computer hardware in an efficient manner. What is an Operating System(2) • It is an extended machine – Hides the messy details which must be performed – Presents user with a virtual machine, easier to use • It is a resource manager – Each program gets time with the resource – Each program gets space on the resource Computer System Components 1. Hardware • Provides basic computing resources (CPU, memory, I/O devices). 2. Operating system • Controls and coordinates the use of the hardware among the various application programs for the various users. 3. Applications programs • 4. 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. Abstract View of System Components Architecture of Unix System Other Application Programs who kernel Hardware vi date History of Operating Systems (1) • First generation 1945 - 1955 – vacuum tubes, plug boards • Second generation 1955 - 1965 – transistors, batch systems • Third generation 1965 – 1980 – ICs and multiprogramming • Fourth generation 1980 – present – personal computers History of Operating Systems (2) Early batch system – bring cards to 1401 – read cards to tape – put tape on 7094 which does computing – put tape on 1401 which prints output History of Operating Systems (3) Structure of a typical FMS job – 2nd generation History of Operating Systems (4) • Multiprogramming system – three jobs in memory – 3rd generation Operating System Concept • • • • Processes Files System Calls The shell Operating System Concept: Process(1) • A process is basically a program in execution • Each process is associated with its address space which contains code segment, data segment, stack segment etc.) • A process can open several files. • Multitasking operating system – Can run multiple processes concurrently. Example: UNIX, LINUX,WINDOWS – A process table is maintained by Operating System (OS) to keep track of these processes. Operating System Concept: Process(2) • A process can create one or more child processes – A created two child processes, B and C – B created three child processes, D, E, and F • Inter Process Communication (IPC) – Sometimes it is needed to communicate between two processes. Operating System Concept: Process(3) Two processes connected by a pipe Operating System Concept: File(1) • A directory groups files/subdirectory together • A directory has entry for files and subdirectory • Each process has a file descriptor table (FDT) to keep track of its open files. Operating System Concept: File(2) File system for a university department Operating System Concept: File(3) • Before mounting, – files on floppy are inaccessible • After mounting floppy on b, – files on floppy are part of file hierarchy Operating System Concept: System Call(1) • The interface between the OS and the user program is defined by a set of instructions called System calls. • Example – count = read(file,buffer,nbyte) Operating System Concept: System Call(2) Operating System Concept: System Call(3) Operating System Concept: System Call(4) Operating System Concept: System Call(5) Operating System Concept: System Call(6) Some Win32 API calls Operating System Concept: Shell(1) • It is the primary interface between a user sitting at his terminal and the OS. • Though it is not a part of the OS, it serves as a good example of how the system calls cab be used. • When a user logs in, a shell is started up. Operating System Concept: Shell(2) • If the user now types date for example, the shell creates a child process and runs the date program as the child. • While the child process is running, the shell waits for it to terminate. • When the child finishes, the shell types the prompt again and tries to read the next input.