Lecture 16: Operating Systems Intro to IT COSC1078 Introduction to Information Technology Lecture 16 Operating Systems James Harland

Lecture 8: VideoIntro to IT Introduction to IT 1 Introduction 2 Images 3 Audio 4 Video 5 Binary Representation WebTest 1, Assignment 1 6 Data Storage 7 Review/Machine Processing 8 Operating Systems WebLearn Test 1 9 Processes Assignment 2 10 Internet 11 Internet Security WebLearn Test 3 12 Future of ITAssignment 3, Peer and Self Assessment

Lecture 16: Operating SystemsIntro to IT Overview  Questions?  Assignments 1 & 2  WebTest 2  Operating Systems  Questions?

Lecture 16: Operating SystemsIntro to IT WebTest 2  Now open  Based on Computer Fundamentals material  Some questions slightly different to what we have covered

Lecture 16: Operating SystemsIntro to IT 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

Lecture 16: Operating SystemsIntro to IT Initial State When Turned On Program Counter Instruction Register 00 ROM RAM ProcessorMemory Disk Bootstrap Program 00

Lecture 16: Operating SystemsIntro to IT Load Bootstrap Program Program Counter Instruction Register 00 ROM RAM ProcessorMemory Disk Bootstrap Program 00

Lecture 16: Operating SystemsIntro to IT Bootstrap program loads OS Program Counter Instruction Register 00 ROM RAM ProcessorMemory Disk Bootstrap Program 00

Lecture 16: Operating SystemsIntro to IT Bootstrap program loads OS Program Counter Instruction Register 00 ROM RAM ProcessorMemory Disk Bootstrap Program 00

Lecture 16: Operating SystemsIntro to IT Bootstrap program has loaded OS Program Counter Instruction Register AA ROM RAM ProcessorMemory Disk Bootstrap Program 00 AA

Lecture 16: Operating SystemsIntro to IT OS takes over execution Program Counter Instruction Register AA ROM RAM ProcessorMemory Disk Bootstrap Program 00 AA

Lecture 16: Operating SystemsIntro to IT Starting Up Operating Systems Program Counter Instruction Register AA ROM RAM ProcessorMemory Disk Bootstrap Program 00 AA

Lecture 16: Operating SystemsIntro to IT Starting Up Operating Systems Program Counter Instruction Register AA ROM RAM ProcessorMemory Disk Bootstrap Program 00 AA

Lecture 16: Operating SystemsIntro to IT Starting Up Operating Systems Program Counter Instruction Register AA ROM RAM ProcessorMemory Disk Bootstrap Program 00 AA

Lecture 16: Operating SystemsIntro to IT Multiple boot scenario … Program Counter Instruction Register 00 ROM RAM ProcessorMemory Disk Bootstrap Program 00

Lecture 16: Operating SystemsIntro to IT Multiple boot scenario … Program Counter Instruction Register 00 ROM RAM ProcessorMemory Disk Bootstrap Program 00

Lecture 16: Operating SystemsIntro to IT Multiple boot scenario … Program Counter Instruction Register 00 ROM RAM ProcessorMemory Disk Bootstrap Program 00

Lecture 16: Operating SystemsIntro to IT Multiple boot scenario … Program Counter Instruction Register 00 ROM RAM ProcessorMemory Disk Bootstrap Program 00

Lecture 16: Operating SystemsIntro to IT OS Software Classification Software SystemApplication Utility Kernel Operating System Shell

Lecture 16: Operating SystemsIntro to IT Processes

Lecture 16: Operating SystemsIntro to IT Processes A program is a static set of instructions A processes is the execution of a program, which changes state over time.

Lecture 16: Operating SystemsIntro to IT Processes Executing in Context Program Counter Instruction Register CC ROM RAM ProcessorMemory Disk 00 CC

Lecture 16: Operating SystemsIntro to IT Processes Executing in Context Program Counter Instruction Register DD ROM RAM ProcessorMemory Disk 00 CC DD

Lecture 16: Operating SystemsIntro to IT Processes Switching Ready Waiting Scheduler maintains process table

Lecture 16: Operating SystemsIntro to IT Processes Switching

Lecture 16: Operating SystemsIntro to IT 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

Lecture 16: Operating SystemsIntro to IT Processes Executing in Context Program Counter Instruction Register BB ROM RAM Processor Memory Disk 00 BB

Lecture 16: Operating SystemsIntro to IT Processes Executing in Context Program Counter Instruction Register 11 ROM RAM Processor Memory Disk 00 BB

Lecture 16: Operating SystemsIntro to IT Processes Executing in Context Program Counter Instruction Register FF ROM RAM Processor Memory Disk 00 FF

Lecture 16: Operating SystemsIntro to IT 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

Lecture 15: Operating SystemsIntro to IT Conclusion  Work on Assignment 2  Web Quizzes and Web Test 2  Finish reading book!