2. Welcome to CMPE003 Personal Computers: Hardware and Software Dr. Chane Fullmer Fall 2002 UC Santa Cruz

3. September 27, 2002 2 Assignments Details on the class web page: http://www.soe.ucsc.edu/classes/cmpe003/Fall02/ TAs Dyng Au Dat Nguyen Sections Monday – 9 -11AM, SS 1 #135 Tuesday/Thursday – 11 – 12PM, JBE #109 Friday – 9 – 11AM, JBE #109

4. September 27, 2002 3 1 st Homework Due Today by 11:59PM NOTE: This homework must be completed successfully to continue in this class If this homework is not received by the due date, you will be dropped from the class No adds will be allowed after this due date -- no exceptions Due Today…… Must be turned in TODAY by 11:59 PM

5. September 27, 2002 4 2 nd Homework Due October 4, 2002 Web Search Exercise See class web page for details http://www.soe.ucsc.edu/classes/cmpe003/Fall02/

6. September 27, 2002 5 Midterm #1 Friday – October 11 Chapters 1 – 5 ~50 questions Multiple choice Bring scantron number F-1712-ERI-L (big & pink) Bring your student ID Required to take exam

7. OPERATING SYSTEMS Software in the Background Chapter 2 Part B Resource Allocation

8. September 27, 2002 7 Objectives of Chapter 2 Describe the functions of an Operating System Explain the basics of a personal computer operating system Describe the advantages of a graphical operating system Differentiate among different operating systems Explain the need for network operating systems Describe the methods of resource allocation on large computers Be able to describe the differences among multiprocessing, multiprogramming, and timesharing Explain the principles of memory management List several functions typically performed by utility programs

9. September 27, 2002 8 Operating System Hidden Software Definition – provides access to all resources Kernel Manages the operating system Memory resident Loads set of programs that lies between applications software and the hardware Fundamental software that controls non-resident portions of the OS as needed Booting – Loads the kernel into memory

10. September 27, 2002 9 Functions of OS Manage the computer’s resources CPU Memory Disk drives Printers Establish a user interface Executes and provides services for applications software Carries out all input and output operations

11. September 27, 2002 10 What is an OS? Machine/resource manager. Physical Devices Microarchitecture Instruction Set Architecture Operating System Utilities, Editors, etc. Hardware Application programs

12. September 27, 2002 11 Large Computer OSs Used by many people at once OS works “behind the scenes” so users can share resources OS must control Who gets access to resources What keeps the programs from different users from getting mixed up with one another

13. September 27, 2002 12 Resource Allocation Resource – hardware or software that is needed to complete a task Resource Allocation – assigning computer resources to certain programs Resource De-allocation – releasing resources when a task is complete

14. September 27, 2002 13 Deadlocks Shared data/resource may lead to deadlock: processes get “stuck”. Example: v is using r1 and requests r2; w is using r2 and requests r1. wv r1r2

15. September 27, 2002 14 Allocating the CPU One CPU Multiprogramming (aka Multitasking) Event-driven Timesharing More than one CPU Multiprocessing – multiple CPUs can run several programs simultaneously SMP – Symmetrical Multi-Processing

16. September 27, 2002 15 Multiprogramming One CPU Concurrent execution of two or more processes Several processes open at once Only one process can receive the attention of the CPU at any given moment Effective because CPU speeds are many times faster than input/output speeds

17. September 27, 2002 16 Event-driven Multiprogramming One program receives the attention of the CPU Its processing will be interrupted based upon events in the program When processing needs to be temporarily suspended, an interrupt is generated This is a signal to the operating system to evaluate the cause of the interrupt and determine who should now have CPU time

18. September 27, 2002 17 Event-driven Multiprogramming Example Two programs are running – Payroll and Inventory Management Payroll needs to read an employee record Payroll generates an interrupt to read from the disk Normal processing is temporarily suspended The CPU looks at the interrupt and initiates the read operation on the disk drive While waiting for the read to complete, the CPU begins processing the Inventory Management program

19. September 27, 2002 18 Event-driven Multiprogramming Example When the disk read operation is complete, another interrupt is generated Normal processing is temporarily suspended The CPU looks at the interrupt and determines its cause (read the data in from the disk drive for the Payroll program) The CPU will either continue processing the Inventory Management program or return to the Payroll program depending upon their priority

20. September 27, 2002 19 Time-sharing Multiprogramming One program receives the attention of the CPU A small fraction of CPU time is allocated to the program The time slice ends The CPU begins processing a different program Response time can vary based upon the number of users on the system

21. September 27, 2002 20 Sharing Memory Program must be in memory to be executed Problems Programs compete for space May have a very large program Memory space for each program must not overlap

22. September 27, 2002 21 Memory Management The process of providing separate memory space to programs Memory Protection keeps one program from interfering with another

23. September 27, 2002 22 Memory Management Methods Partitions or regions Foreground and background Virtual storage (virtual memory)

24. September 27, 2002 23 Partitions or Regions Divide memory into sections (ie, partitions) The partition must accommodate the largest possible program Problem May cause wasted memory space

25. September 27, 2002 24 Foreground and Background Programs are placed in either Foreground or Background Programs in Foreground have priority for CPU time While performing read / write operations for the Foreground program, the CPU gives time to a program in Background Programs are placed in a holding queue while waiting to run

26. September 27, 2002 25 Virtual Storage Virtual Memory Uses concept of Paging Divide the program into equal-size pieces (pages) Store each piece in equal-size memory spaces (page frames) Typical size is 2KB or 4KB Create an index to each page and store in a Page Table

27. September 27, 2002 26 Paging Process A portion of the program is placed in memory The remainder is on disk Sections on disk will be brought into memory as needed (one page at a time) Virtual Storage Virtual Memory

28. September 27, 2002 27 Virtual Storage Virtual Memory Problem -- Thrashing A large portion of CPU time is spent swapping the correct page and bringing it into memory Solution Run fewer programs concurrently Add memory Program design “working set” size – number of pages required in memory for program to run

29. September 27, 2002 28 Memory Protection Keeps one program from straying into another Confines each program to certain defined limits in memory Why needed Possible for one program to destroy or modify another by transferring to the wrong memory location May cause destruction of data Action if assigned memory space is violated Termination of executing program

30. September 27, 2002 29 Sharing Storage Several users need to access the same disk pack One wants to write Another wants to read OS keeps track of the I/O requests OS processes I/O requests in order received

31. September 27, 2002 30 Sharing Printing Resources Print resources are shared between active programs Printouts are generated in pieces as the CPU gives each concurrent program some time Problem The current program may generate a few print lines The CPU moves to the next program The second program may generate a few print lines, etc.

32. September 27, 2002 31 Sharing Printing Resources Result Printout is worthless as it contains a few lines from several programs Solution – Spooling Each program thinks it is writing to the printer The program actually writes to the hard disk When the program is complete, the file on the hard disk is sent to the printer

33. September 27, 2002 32 Additional Printing Problem Printers are slow compared to the CPU speed Solution The CPU writing to the disk The program completes quicker

34. September 27, 2002 33 Utility Programs Come with System Software Handle special needs Perform secondary chores Do not need to be memory resident

35. September 27, 2002 34 Functions of Utility programs File manager – provide access to lists of stored files Backup and Restore – make duplicate copies of important files and return the copy to the hard drive if needed File compression – reduces the amount of disk space required by a file Disk defragmenter – reorganize files so they are stored contiguously on disk providing for faster access Device drivers – convert operating system instructions into commands that are known to a specific device

36. September 27, 2002 35 Next Week…. Chapter 3 (Monday) “Applications Software: Getting the Work Done” Chapter 4 (Wednesday/Friday) “The Central Processing unit: What Goes on Inside the Computer”

37. September 27, 2002 36