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7012_3CS446_S06_1_Introduction1.pdf Principles of Operating Systems
CS 446/646
1. Introduction to Operating Systems
René
Doursat
Department of Computer Science & Engineering
University of Nevada, Reno
Spring
20061/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 2
Principles of Operating Systems
CS 446/646
0.Course Presentation
1.Introduction to Operating Systems
2.Processes
3.Memory Management
4.CPU Scheduling
5.Input/Output
6.File System
7.Case Studies
1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 3
Principles of Operating Systems
CS 446/646
1.Introduction to Operating Systems
a.Role of an O/S
b.O/S History and Features
c.Types of
O / S d.Major O/S Components
e.System Calls
f.O/S Software Architecture
g.Examples of O/S
1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 4
Principles of Operating Systems
CS 446/646
1.Introduction to Operating Systems
a.Role of an O/S
One layer in a computer system architecture
Top-down view: convenient user interface
Bottom-up view: efficien
t resource m a nagerSoftware view: a program that can evolve
b.O/S History and Features
c.Types of
O / S d.Major O/S Components
e.System Calls
f.O/S Software Architecture
g.Examples of O/S
1.a Role of an Operating System
Software layer in a computer system architecture
Silber
sc h a t z , A ., Ga lvin, P . B . and Gagne . G . (2003 ) Oper at ing Syst ems Con c e p t s w i t h Jav a (6t h Ed ition).Abstract view of the com
ponents of a computer systemThe Silberschatz "pyramid" view
1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 5
Tan e n b aum, A . S . (200 1) Mode rn Oper at ing S y st ems (2nd Edition) .1.a Role of an Operating System
Software layer in a computer system architecture
The Tanenbaum "layered" view
A computer system consists of hardware, system programs and application programs1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 6
1.a Role of an Operating System1.a Role of an Operating System
Software layer in a computer system architecture
St a llings, W . (2004 ) Oper at ing Syst ems: I n t e rnals an d Design Prin ciples (5t h Ed ition ) .Layers and views of a computer system
The Stallings "stairs" view
1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 7
1.a Role of an Operating System1.a Role of an Operating System
Software layer in a computer system architecture
How are they all connected?
The Molay "aquarium" view
everything must transit through the O/S or "kernel" disks printers users applicationsThe ker
nel manages all connectionsMolay, B
. (2002 ) Unde r s t anding Unix/ L inux Prog ram m ing (1st Ed ition). user space kernel space1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 8
1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 9
1.a Role of an Operating System
Software layer in a computer system architecture
A computer system consists of (bottom-up):
1. hardware 2. firmware (BIOS) 3. operating system 4. system programs 5. application programs 6. users1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 10
1.a Role of an Operating System
Software layer in a computer system architecture
1.Hardware
provides basic computing resourcesCPU, memory, disk, other I/O devices
2.Firmware (BIOS)
software permanently stored on chip (but upgradable) loads the operating system during boot 3.Operating system
controls and coordinates the use of the hardware among the various application programs for the various users
1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 11
1.a Role of an Operating System
Software layer in a computer system architecture
4.System programs
basic development tools (shells, compilers, editors, etc.) not strictly part of the core of the operating system 5.Application programs
define the logic in which the system resources are used to solve the computing problems of the users compilers, database systems, video games, business programs, etc. 6. Users people, other computers, machines, etc.1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 12
1.a Role of an Operating System
Software layer in a computer system architecture
Key notion
: An operating system is a program that acts as an intermediary between a user of a computer and the computer hardware.1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 13
1.a Role of an Operating System
Software layer in a computer system architecture
Top-down (user) view
the O/S is a convenient application interface the O/S hides the messy details which must be performed the O/S presents user with a virtual machine easier to useBottom-up (hardware) view
the O/S performs efficient resource usage and management time multiplexing: each program gets to use a resource space multiplexing: each program gets part of a resourceSoftware layer view
the O/S is an evolvable and scalable software the O/S permits effective development and introduction of new system functions without interfering with service1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 14
1.a Role of an Operating System
Top-down view: convenient user interface
O/S processesJava VM
by t e c odesGUI IDE
button button w i ndow text widgetsWord Processor
documentsWeb Browser
pa gesThe middleware / componentware paradigm
Var i ous middleware / componentware framewor ks1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 15
1.a Role of an Operating System
Top-down view: convenient user interface
The middleware / componentware paradigm
in this paradigm, the O/S is a "container" or platform the user applications are the "components" that live in the containerthe O/S takes care of the low-level "plumbing" environment around the applications, so that the applications can focus on their internal logic and purpose
the O/S provides services to the applications, not the least execute them same paradigm in other middle ware frameworks: Java virtual machine, GUI environment, Web browser, etc.1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 16
1.a Role of an Operating System
Top-down view: convenient user interface
Services provided by the O/S to user applications
program execution access to I/O devices controlled access to files communications error detection and response1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 17
1.a Role of an Operating System
Top-down view: convenient user interface
Program execution
the O/S loads programs and data into memory, initializes I/O devices and files, schedules the execution of programsAccess to I/O devices
the O/S hides I/O device details from applications (direct I/O access is forbidden) and offe rs a simplified I/O interfaceControlled access to files
the O/S organizes data into files, controls access to the files (create, delete, read, write) and preserves their integrity1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 18
1.a Role of an Operating System
Top-down view: convenient user interface
Communications
the O/S allows exchange of information between processes, which are possibly executing on different computers
Error detection and response
the O/S properly handles hardware failures and software errors with the least impact to running applications (ending, retrying or reporting)1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 19
1.a Role of an Operating System
Top-down view: convenient user interface
Summary: viewed from the user side, the operating system is like a "mandatory middleman": on the one hand it forbids you to directly access hardware resources, you must talk to it first on the other hand it provides you with excellent service and simplifies your life, so you woul dn't want it any differently anyway1.a Role of an Operating System
Bottom-up view: efficient resource manager
St a llings, W . (2004 ) Oper at ing Syst ems: I n t e rnals an d Design Prin ciples (5t h Ed ition ) .The operating system as r
esour ce managerManaging the hardware "plumbing"
1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 20
1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 21
1.a Role of an Operating System
Bottom-up view: efficient resource manager
Managing the hardware "plumbing"
in order to offer services to t he user programs, the O/S "turns around" and manages the inne r workings of the hardware it needs to ensure efficient operation of the computer system it controls the movement, storage and processing of data the O/S is a peculiar form of control, though: it is not a distinct and separa te part of what it controls it is just a program like any other program executed by the processortherefore, it must frequently relinquish control and depend on the processor to allow it to regain control
1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 22
1.a Role of an Operating System
Bottom-up view: efficient resource manager
Duties performed by the O/S as a resource manager
resource allocator operation control program system access accounting and statistics1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 23
1.a Role of an Operating System
Bottom-up view: efficient resource manager
Resource allocator
the O/S is a program that allocates resources to multiple users and multiple jobs running at the same time ("pecking order")
Operation control program
the O/S is a program that controls the execution of user programs ("supervisor") and operati ons of I/O devices ("driver")System access
the O/S ensures that all access to resources is protected, including authorization, conflict resolution, etc. ("guardian")Accounting and usage statistics
the O/S keeps performance monitoring data ("auditor")1/24/2006 CS 446/646 - Principles of Operating Systems - 1. Introduction 24
1.a Role of an Operating System
Note : There is no clear-cut separationbetween the services of an operating system as an application interface and its duties as a hardware manager.The distinction is rather between what
an O/S has to offer and how itdoes it.For example, resolving concurrency is both a user service and a resource management technique.