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1st lecture (August 13, 2015)

by: Andreas

1st lecture (August 13, 2015) CZ2005, CE2005

GPA 4.56
Operating Systems
Cai Wentong, Chng Kee Wah, He Bingsheng, Leong Yin Yoke Junie

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About this Document

This is the 1st lecture. Referenced from lecturer and lecture notes. Email me if you have any suggestion or else
Operating Systems
Cai Wentong, Chng Kee Wah, He Bingsheng, Leong Yin Yoke Junie
Class Notes
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This 7 page Class Notes was uploaded by Andreas on Monday August 31, 2015. The Class Notes belongs to CZ2005, CE2005 at Nanyang Technological University taught by Cai Wentong, Chng Kee Wah, He Bingsheng, Leong Yin Yoke Junie in Summer 2015. Since its upload, it has received 54 views. For similar materials see Operating Systems in Computer Science and Engineering at Nanyang Technological University.

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Date Created: 08/31/15
Operating System OS Intermediate program software between user and computer hardware Every program that user wants to run and every result that returned to the user has to pass through OS first Goals Role Convenience user perspective makes the computer easier to use Efficiency hardware perspective makes use of computer hardware in an efficient way gt better performance lower cost Important to be understood in order to design suitable OS Can sometimes cause conflictproblem gt good GUI convenience sacrifices performance speed efficiency 0 Windows Vista gt fail product Resource allocator 0 Decide which application get which resources at what time Control program 0 Make sure every process is legal and no process interferes with one another 0 Controls the execution of application program and IO operation System kernel 0 A program that runs at all times 0 Always ready to receive new instructions Computer Components Hardware 0 Basic computing resources 0 CPU memory IO devices 0 Can have different types of hardware Application programs 0 Programs that isn t running at all time 0 Manage the usage of system resources to solve user s enquiries 0 Word processors spreadsheets compilers games etc Users 0 In the form of people machinery or other computers in a networkeddistributed system Between those three components there is a problem gt solved with OS OS 0 Controls 0 Some application may malfunction or be very selfishgreedy want to use all resources in shared environment 0 Manages the errors and problems 0 Coordinates o Allocate and guarantee access of applications to its required resources Computer Systems Mainframe systems 0 In first generation there is setup cost for every job 0 Goal favors efficiency better performance over convenience Simple batch systems 0 To reduce the cost jobs with similar resources are batch together mega jobquot Setup once then run the whole batch 0 Needs to know which job to run first gt automatic job sequencing allocate the jobs 0 Nonpreemptive gt once a job starts the other need to O wait 0 Very simple memory layout gt in memory one job at a time Memory divided in 2 parts OS and application program Efficiency problem gt CPU will be idle when a job is waiting for IO input low CPU utilization o Programmer needs to manually setup everything amount of memory CPU time needed etc Multiprogrammed systems 0 Runs multiple jobs at the same time 0 Load several jobs in main memory then multiplexed the CPU between them When CPU is idle it will given another job in memory 0 Higher CPU utilization gt job switching reduce idle time 0 Features needed Memory management gt allocate memory for new job reallocate memory for another job at termination CPU scheduling gt choose what is the order of execqun Devices allocation gt shared between multiple jobs Timesharingmultitasking systems 0 Logical extension of multiprogrammed system 0 CPU executes a large number ofjobs that can be swap in and out of main memory gt functionality of virtual memory 0 0 CPU frequently switch between jobs so that users can still interact with the system in the process gt stronger user interaction User can input command gt runs onine executed one after another Interactive gt user will be waiting Desktop systems 0 Personal computers gt usually to be used by 1 user only 0 Has a lot of IO devices gt mouse screen printer speaker keyboard etc 0 Hardware driver can be a huge part in the code base 0 Goal favors convenience fast response over efficiency gt better GUI 0 May have several OS installed gt MacOS Windows Linux etc Multiprocessorparallel systems 0 Multicore design 0 Prove that OS development can be caused by hardware development 0 Use same main memory but has its own registers and caches MultiCPU design Tightly coupled gt usually use the same memory 0 Increase performance throughput Lower cost gt some hardware are shared memory IO etc 0 Higher reliability gt failure in 1 core or CPU doesn t stop the whole system from working Special OS Realtime systems 0 Have welldefined specific constraints on execution time gt must finished in time no matter what 0 Commonly used as control device in specialized application scientific medical industrial etc 0 GPS LynxOS RTLinux VxWorks etc Handheldembedded systems 0 Mobile phones tablets pads 0 Windows Phone iOS Android 0 Special issues 0 Limited memory and battery gt much lower than PC 0 Much slower processors 0 Smaller display screens gt need clipping to be able to display all content needed System Operation Devices connect to the computer by shared system bus CPU and IO devices can execute simultaneously but need to take turns to use the bus Every device controller takes care of a particular type of device responsible for its functionality gt CPU cannot access device directly Controller has its own buffer to store data temporarily in between the transferring The controller moves data through buffer first before going through memory Controller informs CPU in the time of termination process is done by sending interrupt signal gt CPU stops current process and switch to execute device s process interrupt is prioritize above other processes Interrupt amp DMA Interrupt Different OS handle interrupts differently depends on their system The handling routines are fixed and stored in the form of array of code interrupt vector gt interrupt service routine ISR Interrupt vector store the starting address of each ISR Interrupt vector and ISR are data structures stored in main memory area of OS kernel space Interrupts are processed 1 at a time gt while an interrupt is processed the other need to be disabled prevent lost interrupt Trap 0 Interrupt generated by software 0 Caused by error unhandled exception user s request to OS via system call OS is interrupt driven gt idle when there is no interrupt If not OS will always need to ask forjob completion polling which is very inefficient takes CPU time HandHng 0 OS save current execution state state of all CPU component gt program counter registers gt large overhead 0 Read CPU register and check the type of interrupt that is coming 0 Find the particular ISR through interrupt vector and execute it The most common usage is interrupt 10 in lowspeed IO devices If it used in highspeed devices there will be more CPU time used to handle the interrupt lower efficiency Direct memory access DMA Used as substitute for interrupt in highspeed IO devices Mainly to transmit information in a fast way OS sets up buffer pointers and counters before moving blocks of data from buffer to memory directly Only 1 interrupt will be send for each block and CPU is not used in the transfer process


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