cosc1078 introduction to information technology lecture 14 operating systems

Lecture 14: Operating Systems Intro to IT

COSC1078 Introduction to Information Technology

Lecture 14

Operating SystemsJames Harland

[email protected]


Introduction

James Harland• Email: [email protected]• URL: www.cs.rmit.edu.au/~jah• Phone: 9925 2045• Office: 14.10.1 • Consultation: Mon 4.30-5.30, • Thu 11.30-12.30What colour is my office

door? Carpet? Chair?


Introduction to IT1 Introduction 2 Images3 Audio4 Video WebLearnTest 1 5 Binary Representation Assignment 16 Data Storage7 Machine Processing8 Operating Systems WebLearn Test 29 Processes Assignment 210 Internet11 Internet Security WebLearn Test 312 Future of IT Assignment 3, Peer and Self Assessment


Overview Questions?

Assignments 1 & 2

Operating Systems

Questions?


Assignments 1& 2

Assignment 1 Currently being marked Will have marks out later this week

Assignment 2 Specification has been published Must be done in groups of 2 or 3 Can change groups from Assignment 1 (if you wish) Must have a blog on Blackboard

Lecture 14: Operating Systems SE Fundamentals

Questions?

How did you spend 6-8 hours on this course last week? This week?


Operating Systems

operating system

kernel device driver

open source real time

virtual machine

desktop publishing


Operating Systems

Operating system


Operating Systems Manage hardware and software resources Memory allocation Prioritising requests and processes Controlling input and output devices Managing network access Managing file systems Dealing with multiple users …


Operating Systems

HARDWAREHARDWARE

USER


Operating Systems


Operating Systems Concurrent execution of processes on a single

CPU Memory management

Registers, caches, RAM, hard disk, plug-ins, ...Movement of data between these

File systems Networking

Printers, scanners, LAN, wireless, Internet, ...


Operating Systems Graphical User Interface (GUI)

Colors, data, cursors, ... Device drivers

Code specialised for particular hardware device (DVD writer, printer, monitor, ...)Controls access to these

Security Passwords, file sharing, protocols, ...


Operating Systems Desktop (Windows, MacOS, Linux, ... )

Windows around 85% of market Server systems

Google “back end”, server farms, ... Windows Server or Unix

Specialist systems Supercomputers, call centres, real-time

systems, PDA systems, ...


Operating Systems


Linux Open source Developed in 1991 by Linus Torvalds Written in C RedHat, Mandrake, SUSE, Ubuntu, ... RedHat 7.1 has30 million+ lines of code


Windows Add-on to MS-DOSin 1985 Most popular OS Known securityissues Windows XP 40 million lines of code Vista released 2007 Windows 7 (now!)


MacOS Only on Apples Introduced by Apple in 1984 GUI from the start Based on Unix Graphics features Mac OS X Leopard


Where to begin?How do you start an operating system?Boot it! (or bootstrap)

Turn on power ()

Machine loads bootstrap program from ROM (non-volatile memory)

Bootstrap program loads OS

OS takes over


Initial State When Turned On

Program Counter

InstructionRegister

00 ROM

RAM

Processor Memory Disk

BootstrapProgram

00


Load Bootstrap Program

Program Counter

InstructionRegister

00 ROM

RAM


BootstrapProgram

00



Program Counter

InstructionRegister

00 ROM

RAM


BootstrapProgram

00


Bootstrap program has loaded OS

Program Counter

InstructionRegister

AA ROM

RAM


BootstrapProgram

00

AA


OS takes over execution

Program Counter

InstructionRegister

AA ROM

RAM


BootstrapProgram

00

AA


Starting Up Operating Systems

Program Counter

InstructionRegister

AA ROM

RAM


BootstrapProgram

00

AA


Multiple boot scenario …

Program Counter

InstructionRegister

00 ROM

RAM


BootstrapProgram

00


OS Software Classification

Software

SystemApplication

Utility

Kernel

Operating System

Shell


Processes


Processes

A program is a static set of instructions

A processes is the execution of a program, which changes state over time.


Processes Executing in Context

Program Counter

InstructionRegister

CC ROM

RAM


00

CC



Program Counter

InstructionRegister

DD ROM

RAM


00

CC

DD


Processes Switching

Ready

Ready

Waiting

Scheduler maintains process table


Processes Switching


Interrupts Signals to the CPU Often generated by timing circuits CPU reacts by jumping to appropriate memory location

Dispatcher selects a ready process resets timing circuit starts process

CPUs often designed to switch process states efficiently



Program Counter

InstructionRegister

BB ROMRAM

Processor Memory Disk00

BB



Program Counter

InstructionRegister

11 ROMRAM


BB



Program Counter

InstructionRegister

FF ROMRAM


FF


Interrupts Provide mechanism to switch processes

CPU doesn’t have to wait for I/O transfers

Switching leads to faster throughput

`Save document’ means CPU does something else while the save takes place


Conclusion

Work on Assignment 2

Web Quizzes and Web Test 2

Finish reading book!

cosc1078 introduction to information technology lecture 14 operating systems

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