CS307 Operating Systems Operating Systems Introduction Fan Wu Department of Computer Science and Engineering Shanghai Jiao Tong University Spring 2020 Operating Systems 2 Operating Systems Four Components of a Computer System UNIX-family: BSD(Berkeley Software Distribution), System-V, GNU/Linux, MINIX, Nachos, OS X, iOS People, machines, other BSD-family: FreeBSD, NetBSD, OpenBSD computers System-V-family: AIX, HP-UX, IRIX, Solaris Linux-family: Red Hat, Debian, Ubuntu, Fedora, openSUSE, Linux Mint, Application programs Google's Android, WebOS, Meego define the ways in which theSystem system programs resources are MS-DOS, Microsoft Windows, Windows Mobile, Win-CE, WP8 arecomputer used to software solve the AmigaOS computingdesigned to problems operate theof thecomputer users hardware and Symbian, MeeGo toControls provide and a platform coordinates for Google Chrome OS runninguse of hardware application among programsvarious applications and OS/2 users XrossMediaBar(XMB) for PS3, Orbis OS for PS4 provides basic computing Input Output System for Wii resources Tiny-OS, LynxOS, QNX, VxWorks Operating Systems 3 Operating Systems 4 Computer System Structure What is an Operating System? Hardware – provides basic computing resources An operating system is a program that manages the computer hardware CPU, memory, I/O devices A program that acts as an intermediary between the computer user and the Operating system – Controls and coordinates use of hardware among computer hardware various applications and users System programs – are computer software designed to operate the computer hardware and to provide a platform for running application Operating system goals: programs Execute user programs and make solving user problems easier BIOS and device drivers Make the computer system convenient to use Application programs – define the ways in which the system resources Use the computer hardware in an efficient manner are used to solve the computing problems of the users Word processors, compilers, web browsers, database systems, video games Users People, machines, other computers Operating Systems 5 Operating Systems 6 1 Operating System Definition Operating System Definition (Cont.) No universally accepted definition OS is a resource allocator Manages all resources “Everything a vendor ships when you order an operating system” is good Decides between conflicting requests for efficient and fair resource use approximation But varies wildly OS is a control program “The one program running at all times on the computer” is the kernel. Controls execution of programs to prevent errors and improper use of the computer Everything else is either a system program (ships with the operating system) or an application program. “An operating system (OS) is software, consisting of programs and data, that runs on computers, manages computer hardware resources, and provides common services for execution of various application software.” --- From Wikipedia Operating Systems 7 Operating Systems 8 Operating System Structures Virtual Machines (a) Bare Machine (b) Virtual Machine Operating Systems 9 Operating Systems 10 Course Outline Process Scheduling •Main Memory •Virtual Memory MEMORY MANAGEMENT •Processes •File-System Interface •Threads •File-System •CPU PROCESS STORAGE Implementation Scheduling MANAGEMENT MANAGEMENT •Mass-Storage •Process Structure Synchronization •I/O Systems •Deadlocks OPERATING SYSTEMS DISTRIBUTED SYSTEMS Operating Systems 11 Operating Systems 12 2 Single and Multithreaded Processes CPU Scheduling First-Come, First-Served (FCFS) Scheduling Shortest-Job-First (SJF) Scheduling Priority Scheduling Round-Robin Scheduling Multilevel Queue Scheduling Multilevel Feedback Queue Scheduling Operating Systems 13 Operating Systems 14 Process Synchronization Deadlock Avoidance Example of Banker’s Algorithm Dining-Philosophers Problem 5 processes P0 through P4; Philosophers spend their lives thinking and eating 3 resource types: Don’t interact with their neighbors, occasionally try to pick up 2 chopsticks A (10 instances), B (5 instances), and C (7 instances) (one at a time) to eat from bowl Snapshot at time T : Need both to eat, then release both when done 0 Max Allocation Need Available In the case of 5 philosophers A B C A B C A B C A B C Shared data P0 7 5 3 0 1 0 7 4 3 3 3 2 Bowl of rice (data set) P1 3 2 2 2 0 0 1 2 2 Semaphore chopstick [5] initialized to 1 P2 9 0 2 3 0 2 6 0 0 P3 2 2 2 2 1 1 0 1 1 P4 4 3 3 0 0 2 4 3 1 The system is in a safe state since the sequence < P1, P3, P0, P2, P4> satisfies safety criteria Operating Systems 15 Operating Systems 16 Memory Management Virtual Memory Management Paging Hardware Operating Systems 17 Operating Systems 18 3 Mass-Storage Systems File-System cylinder 7 0 15 8 sector 6 1 14 9 13 5 10 2 11 block 12 4 3 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 …… Combined Scheme with UNIX I-node Operating Systems 19 Operating Systems 20 I/O Systems Distributed System Structure Operating Systems 21 Operating Systems 22 Homework Reading Chapter 1: Introduction Operating Systems 23 4.