1 Application & Systems Software Operating Systems – a deeper look

2 Included in today’s work: Follow up Lecture What is an Operating System (OS)? What different types are there? A deeper look at Operating Systems Some finer points of MS-DOS Files and Directories Extending the command set

3 What are Operating Systems? They define our computing experience. First software we see when we turn a computer on. ‘Enables’ all the programs we use. Organises and controls all the hardware. Hides the details of all the actual processing from the user.

4 Some Examples Not all computers have operating systems. All desktop computers have an OS: –Windows family (95, 98, 2000, NT); –UNIX family (Linux, BSD, UNIX, etc); –Macintosh OS; Hundreds of others: –Mainframes, robotics, manufacturing, etc.

5 So what does an OS do? Manages the hardware and software resources of the computer system: –e.g. processor, memory, disk space. Provides a stable, consistent way for applications to deal with the hardware without having to know all the details of the hardware.

6 Various programs and input methods compete for the attention of the CPU and demand memory, storage and input/output (I/O) bandwidth for their own purposes. The OS acts like a “good parent”, making sure that each application gets the necessary resources, ensuring that the limited capacity of the system is shared out for the greatest good of all users and applications.

7 The provision of an consistent application interface is very important when there is more than one type of computer using the OS. Windows 98, for example, runs on hardware from thousands of vendors and accommodates thousands of different printers, disk drives and special peripherals.

8 Four Types of OS Real-Time OS (RTOS) –Control machinery, scientific instruments and industrial systems. –Very little user interface capability –Very important that a particular operation executes in precisely the same amount of time every time it occurs.

9 Four Types of OS Single-User, Single Task –This OS is designed to manage the computer so that one user can effectively do one thing at a time. –The Palm OS, for Palm computers, is an example of this type of OS.

10 Four Types of OS Single-User, Multi-Tasking –The most common type of OS on desktops and laptops. –e.g. Windows 98, MacOS –You can be writing a note in a word processor while downloading a file from the internet while printing the text of an message.

11 Four Types of OS Multi-User –Allows many different users to take advantage of the computer’s resources simultaneously. –Needs to make sure that the requirements of the various users are balanced. –Examples include Unix, VMS and mainframe operating systems

12 Four Types of OS Don’t confuse multi-user operating systems and single-user operating systems that support networking. Windows 2000 and Novell Netware can each support hundreds or thousands of networked users, but they are not true multi-user operating systems

13 Basic Functions of OS Wake-Up Call –The first program that runs is usually a set of instructions kept in the computers ROM. This examines the system hardware to make sure everything is functioning properly –This is the Power-On Self Test (POST) –After POST, the software loaded in ROM will begin to activate the computer’s disk drives. –In most modern computers, the first bit of OS loaded is the bootstrap loader.

14 Bootstrap Loader 1 single function –Loads the OS into memory and allows it to begin operation Sets up the small driver programs that interface with and control the various hardware sub-systems of the computer. Divides the memory into those bits that hold the OS, user information and applications. Finally turns control of the computer over to the OS

15 OS Tasks Falls into 6 general categories –Processor management –Memory management –Device management –Storage management –Application interface –User interface

16 Processor management Managing the processor concerns two issues: ensuring that each process & application receives enough CPU time maximising the number of CPU cycles used for real work The OS controls and schedules processes. It handles interrupts, and prioritises tasks

17 Memory Management Two tasks are performed: the OS works out how much memory to allocate to a particular process the OS decides which type of memory in the system can be used for which part of each process The crucial factor here is the different types of memory and their speeds.

18 Device Management Each peripheral requires a driver This is a special program to translate between the hardware and high-level programming languages. Part of the OS function is to communicate with these drivers and to assign priorities to data and commands going to and coming from the device.

19 Storage management Drivers are also used to manage memory storage peripherals e.g. disks, tape etc. One function of the OS is to configure and manage part of the storage device for virtual memory. A further function of the OS is to determine which parts of “current processes” are consigned to this virtual memory. A third function is that of file manager, to keep track of and to recall all the files and programs stored in the device.

20 Application interface An Application Program Interface (API) allows Application programmers to use and program various functions of the computer and OS without needing to know all the details of the CPU operations. Such an API may, for example allow a programmer access to disk storage and to read mouse commands, without having to worry about the different kinds of disks and mice which might be used.

21 User Interface The UI provides a consistent way for the user to interact with the computer, which is common to all models and manufacturers There are two main types of UI: –Graphical User Interface (eg Windows) –Command Line Interface (e.g MS-DOS) Other Operating Systems may deliver a mixture of these two.

22 Finding out more about Operating Systems The information presented here is an introduction to a very extensive subject. You should follow up some of these ideas by: –reading the IMC booklet for weeks 7 & 8 –reading ch. 2 & 3 of the set book. – system.htmhttp:// system.htm

23 A brief overview of MS-DOS When you activate the Command Prompt, a new window should open (called command prompt) and it will probably contain something like: –Microsoft Windows 2000 [version ] (C) Copyright Microsoft Corp. C:\>

24 DOS Conventions All DOS commands are activated by typing the commands and pressing the key. DOS is not case-sensitive. Spaces are the primary separators in DOS commands. One or more spaces must follow each command word, and file names are delimited by spaces – therefore, files names may not contain spaces.

25 The DOS Prompt e.g. C:\WINDOWS\SYSTEM> C: the default disk drive \ the root directory WINDOWS name of a subdirectory in the root SYSTEM name of a directory in the WINDOWS subdirectory >Ready for your command

26 DOS Disk Concepts Each disk drive is assigned a letter A colon after the drive letter identifies it as a drive name, as opposed to a file name The letter is associated with the drive, not the disk. Certain letters –A: = floppy disk –C: = primary hard disk drive

27 DOS File Concepts Files on the disk are named things like Year1.doc, notes.ppt and go.exe etc. A filename potentially has two parts to it: –the filename (up to 8 letters) –the extension (up to three letters) The “.” is merely a separator, used to keep the two elements apart, so that DOS can find files of a particular type.

28 DOS Directory Concepts Files are collected together in folders –so for example a folder called semester1 might contain the documents week1.doc, week2.doc etc. Semester 1 week1.docweek2.docweek3.doc

29 DOS Directory Concepts groups of folders can be put into other folders, –so for example a folder called year1 might contain the folders semester1 and semester2 Year 1 Semester1Semester2 week1.docweek2.docweek3.doc

30 DOS Directory Concepts This process of putting files into folders and folders into other folders continues up to the level of the root directory, the disk drive’s main folder. C:\ IMCBACE Year 1ProgramsGames

31 Directories, Subdirectories If you look in any folder you will see a collection of files and folders Listing the Directory will tell you what is in there. A subdirectory is merely a list of what is in any of the folders within the current directory.

32 Example Directory Structure

33 Listing a Directory Command –dir This command is an instruction to DOS to list the directory for the folder which you have selected. DOS remembers the “position” that you are in the directory structure. This is called the “default”.

34 Directory Commands Other Commands: To put the listing across the screen (Wide) –dir /w To order the listing by name –dir /o To include subdirectories –dir /s

35 Interpreting a Directory Listing Volume in drive A is MINI_BOOT Volume Serial Number is E9 Directory of A:\ COMMANDCOM :00a DEFRAGEXE :00a DEFRAGHLP :00a 3 file(s) bytes bytes free

36 Interpreting a Directory Listing Volume in drive A is MINI_BOOT –Volume label can be given when formatting a disk, or by using the label command Volume Serial Number is E9 –Serial number is assigned automatically when formatting.

37 Interpreting a Directory Listing Directory of A:\ –This disk is in A: drive, and we’re looking at the “root” directory COMMAND COM :00a –A file called command.com, which occupies 52,925 bytes and was last modified at 6 am

38 Interpreting a Directory Listing 3 file(s) bytes –There are three files occupying a total of 137,185 bytes in this directory bytes free –You could store another 1,188,352 bytes on this disk

39 Changing Drives/Directories Make C: the default –c: Make the root default –cd\ Change to winword directory –cd \msoffice\winword Change to the parent directory (one up) –cd..

40 Copying, Deleting, & Renaming Copy from default to a:\ –Copy file.ext a:\ Copy from a:\ to default –Copy a:\file.ext Delete one file –Del a:\file.ext Rename a file.abc to file.xyz –Rename file.abc file.xyz

41 Using Wildcard Characters A Wildcard Character allows you to type in a name without specifying it completely. This means that you can work on all files of a particular type For example, suppose that you wished to find all word files. These have the extension DOC, so you would use specify *.DOC as the filename. The * is a wildcard.

42 Using Wildcard Characters Matching any group of letters –* (star or asterisk) matches any group of letters in the file name after the asterisk Matching any single letter –? (question mark) matches any single letter in the file name.

43 Listing a Directory using wildcards List all files –dir *.* All files with same extension –dir *.ext All files with a particular name, regardless of their extension –dir name.* All files within a specific directory –dir c:\web\site\*.*

44 Creative use of Wildcards dir q*.* –List all files beginning with the letter q copy *.bat b: –Copy all files with the extension bat to drive b: dir budget?a.dat –List files whose name begins with budget, has any single character, ends with a and has the extension dat.

45 Finding out more about DOS Links to help you with DOS Commands MS-DOS Survival Guide q02cd.htmhttp://courses.wccnet.edu/computer/mod/ q02cd.htm EasyDOS Command Index DOS 7 Full Command list