1. CSCI-235 Micro-Computer in Science System Software

2. © Prentice-Hall, Inc System Software  System software includes all of the programs needed to keep a computer and its peripheral devices running smoothly  Two major categories of system software are: Operating systems Operating systems System utilities System utilities

3. © Prentice-Hall, Inc The Operating System  The (OS) is a set of programs that perform certain basic functions with a specific type of hardware  The operating system (OS) is a set of programs that perform certain basic functions with a specific type of hardware  The functions of the OS are: Starting the computer Starting the computer Managing programs Managing programs Managing memory Managing memory Handling messages from input and output devices Handling messages from input and output devices Enabling user interaction with the computer Enabling user interaction with the computer

4. © Prentice-Hall, Inc The Operating System  OS stays behind the scenes  All software depends on the OS OperatingSystem GUI

5. © Prentice-Hall, Inc Operating Systems for Large Computers  Resource allocation Assigning computer resources to certain programs and processes for their use Assigning computer resources to certain programs and processes for their use  Main issues related to resource allocation Sharing the Central Processing Unit (CPU) Sharing the Central Processing Unit (CPU) Sharing memory Sharing memory Sharing storage resources Sharing storage resources Sharing printing resources Sharing printing resources

6. © Prentice-Hall, Inc Sharing the CPU  Multiprocessing  Multiprogramming  Time-Sharing

7. © Prentice-Hall, Inc Multiprocessing  The use of a powerful computer with multiple CPUs  Multiple programs run simultaneously Each runs on its own processor Each runs on its own processor

8. © Prentice-Hall, Inc Multiprogramming  Two or more programs executed concurrently Programs take turns using the CPU Programs take turns using the CPU Event-driven Event-driven An interrupt suspends processing to allow another program to runAn interrupt suspends processing to allow another program to run After the second program runs, the OS returns the CPU to another programAfter the second program runs, the OS returns the CPU to another program

9. © Prentice-Hall, Inc Time-Sharing  Programs take turns using the CPU  Time-driven Each user is given a slice of time (fraction of a second) Each user is given a slice of time (fraction of a second) CPU works only on that user’s tasks during his/her time slice CPU works only on that user’s tasks during his/her time slice  Typically used in applications with many users

10. © Prentice-Hall, Inc Starting the Computer  Booting – The process of loading or reloading the OS into the computer’s memory

11. © Prentice-Hall, Inc Starting the Computer  The computer copies the kernel from the hard drive into the computer’s memory The kernel The kernel Is the central part of the OSIs the central part of the OS Starts all applicationsStarts all applications Manages devices and memoryManages devices and memory Resides in memory at all timesResides in memory at all times Performs other essential functionsPerforms other essential functions

12. © Prentice-Hall, Inc Managing Programs  Single-tasking systems run one application program at a time  Multitasking OSs have the ability to run more than one application program at a time  Multitasking is accomplished by A foreground application A foreground application The active program or program in useThe active program or program in use One or more background applications One or more background applications Inactive program(s) or program(s) not in useInactive program(s) or program(s) not in use

13. © Prentice-Hall, Inc Example of Multitasking Background application Foreground application Foreground application

14. Storage Structure  Programs must be in main memory (RAM) to execute  Von-Neumann architecture Load instruction from memory into instruction register Load instruction from memory into instruction register Operands fetched from memory to internal registers Operands fetched from memory to internal registers START Fetch next instruction from Memory to IR Increment PC Decode and Execute Instruction in IR STOP ? NO YES

15. © Prentice-Hall, Inc Storage Structure  Ideally, we want programs and data to reside in main memory permanently Main memory is usually too small Main memory is usually too small Main memory is volatile – loses contents on power loss Main memory is volatile – loses contents on power loss  Secondary storage holds large quantities of data, permanently Magnetic disk is the most common secondary-storage device Magnetic disk is the most common secondary-storage device Actually, a hierarchy of storage varying by speed, cost, size and volatility Actually, a hierarchy of storage varying by speed, cost, size and volatility

16. Storage-Device Hierarchy

17. Storage Technology  Static RAM (SRAM) 0.5ns – 2.5ns, $2000 – $5000 per GB 0.5ns – 2.5ns, $2000 – $5000 per GB  Dynamic RAM (DRAM) 50ns – 70ns, $20 – $75 per GB 50ns – 70ns, $20 – $75 per GB  Magnetic disk 5ms – 20ms, $0.20 – $2 per GB 5ms – 20ms, $0.20 – $2 per GB  Ideal memory Access time of SRAM Access time of SRAM Capacity and cost/GB of disk Capacity and cost/GB of disk

18. © Prentice-Hall, Inc Managing Memory  The operating system allocates memory areas for each running program; it keeps programs from interfering with each other  The operating system uses virtual memory as an extension of random access memory (RAM)

19. © Prentice-Hall, Inc Managing Virtual Memory least recently used data or program instructions page swapped out swap file Virtual memory management hard disk page swapped in most recently transferred data or program instructions memory

20. Virtual Memory and Cache

21. © Prentice-Hall, Inc Cache/VM: Analogy  You are going to do some research on a particular topic. Thus, you go to the library and look for the a shelve that contains books on that particular topic  You pick up a book from the shelve, find a chair, seat and start reading

22. © Prentice-Hall, Inc Cache/VM: Analogy  You find a reference to another book on the same topic that you are also interested in reading. Thus, you stand up, go to the same shelve, leave the first book and pick up the other book  Then, you go back to the chair and start reading the second book  Later on you realize that you want to read the first book once again (or another related book). Thus, you repeat the same process (i.e., go to the shelve to find it)

23. © Prentice-Hall, Inc Cache/VM: Analogy  Suppose that instead of taking just one book from the shelve, you take 10 books on the same topic. Then, you find a table with a chair, put the 10 books on the table, sit there and start reading one of the books  If you need another related book, there is a good chance that it is on your table so you don’t have to go to the shelve to get it. Also, you can leave the first book on the table and there is a good chance that you will be needing it again later

24. © Prentice-Hall, Inc Handling Input and Output  Input and output devices generate interrupts, or signals, that tell the operating system that something has happened  The OS provides interrupt handlers or mini- programs that begin when an interrupt occurs

25. © Prentice-Hall, Inc Providing the User Interface  The user interface is that part of the OS with which the user interacts with a computer

26. © Prentice-Hall, Inc Types of User Interfaces  Graphical user interface (GUI) Uses graphics to create a desktop environment Uses graphics to create a desktop environment Icons (small pictures) represent computer resources Icons (small pictures) represent computer resources Programs run within on-screen windows Programs run within on-screen windows  Menu-driven Text-based menus are used to show all of the options available to the user Text-based menus are used to show all of the options available to the user  Command-line The user is required to type keywords or commands in order to enter data or give instructions The user is required to type keywords or commands in order to enter data or give instructions

27. © Prentice-Hall, Inc Graphical User Interface (GUI)

28. © Prentice-Hall, Inc Menu-driven User Interface

29. © Prentice-Hall, Inc Command-Line Interface

30. © Prentice-Hall, Inc MS-DOS WINDOWS XP MAC OS LINUX UNIX Popular Operating Systems

31. © Prentice-Hall, Inc Microsoft Windows Click to view each Windows version (1985-2001) Windows 1.0 (1985)Windows 2.0 (1987)Windows 3.x (1990-1992)Windows NT (1993)Windows 95 (1995)Windows 98 (1998)Windows 2000 (2000)Windows ME (2000)Windows XP (2001)

32. © Prentice-Hall, Inc MAC OS  Created in 1984  First OS to use graphical user interface  Easiest operating system for beginners  Mac OS X, was released in 2000

33. © Prentice-Hall, Inc MS-DOS  Developed for IBM PCs in 1981  Uses command-line interface  Use is diminishing

34. © Prentice-Hall, Inc UNIX  Developed by AT&T in 1970s  Developed concepts of file management and path names  Widely used by corporations

35. © Prentice-Hall, Inc Linux  Developed in 1991 by UNIX  Open-source code –Available for all to see and use  More stable than Windows  Powerful and free  Growing acceptance

36. © Prentice-Hall, Inc System Utilities: Tools for Housekeeping  System utilities are programs that help the operating system manage the computer system’s resources  Types of utilities Backup software Backup software Antivirus software Antivirus software Disk scanning Disk scanning Disk defragmentation Disk defragmentation File management File management File-searching software File-searching software File compression File compression

37. © Prentice-Hall, Inc Backup Software  Backup software includes programs that enable the user to copy data from the hard disk to another storage medium

38. © Prentice-Hall, Inc Antivirus Software  Antivirus software protects the computer from computer viruses

39. © Prentice-Hall, Inc File Management Utilities  Known as a file manager  Enables the user to perform various tasks on storage devices using files, folders, and directories  Tasks include: Creating folders Creating folders Saving, deleting, copying, and moving files and folders Saving, deleting, copying, and moving files and folders Examining the contents of files Examining the contents of files Launching application programs Launching application programs

40. © Prentice-Hall, Inc Search  Search programs enable users to find files on storage devices

41. © Prentice-Hall, Inc File Compression Utility  A file compression utility reduces the size of a file

42. © Prentice-Hall, Inc Troubleshooting  Computer startup failure Use a boot disk (emergency disk) in the floppy drive Use a boot disk (emergency disk) in the floppy drive  System slowdown Scan for viruses Scan for viruses Defragment the hard disk Defragment the hard disk