Disk Operating System (DOS)

2. Chapter 2 Disk Operating System (DOS) Finding DOS and Understanding its Strengths and Weaknesses Installing DOS How the FAT File System Works Working with the DOS Command Prompt Understanding the DOS Bootup Process Troubleshooting Common DOS Problems

3. Learning Objectives • Measure the value, strengths, and weaknesses of DOS • Install DOS • Use the FAT file system • Use DOS commands for file management and other tasks • Describe the DOS bootup process and create startup disks • Troubleshoot common DOS problems

4. Finding DOS and Understanding its Strengths and Weaknesses • Versions of DOS • CP/M was an important predecessor to DOS • Many versions of DOS, several introduced by Microsoft (MS) • MS created PC DOS for IBM • Later licensed DOS as MS-DOS to other manufacturers • MS-DOS 5.0 first version available as a separate product

5. Finding DOS and Understanding its Strengths and Weaknesses • Versions of DOS (continued) • PC DOS now works on Microsoft/Intel compatible computers • Digital Research (of CP/M fame) introduced DR-DOS in 1987 • DR-DOS 8.0 introduced in 2004 by DeviceLogics • FreeDOS distributed without charge under GNU GPL license

6. Finding DOS and Understanding its Strengths and Weaknesses • DOS’ Strengths • DOS for backward compatibility with DOS apps • DOS when you need a small OS • DOS is more compact than Windows and hence useful for embedded systems or for portability • DOS is popular as an operating system due to its ability to pack all startup files on a single floppy disk

7. Finding DOS and Understanding its Strengths and Weaknesses • DOS Strengths (continued) • The floppy disk is also known as the startup disk • Startup disk accommodates additional files, such as drivers and utilities • Startup disk can be used for booting up a computer and running special diagnostic programs

8. Finding DOS and Understanding its Strengths and Weaknesses • DOS Weaknesses • Processor mode limits • Memory limits • Multitasking limits • Hard drive limits

9. Finding DOS and Understanding its Strengths and Weaknesses • DOS Weaknesses (continued) • Processor Mode Limits • Only supports real mode of operation of Intel processors • Newer Intel processors start in the real mode, and newer OSs (Windows, Linux, UNIX) switch the processor from the real mode to the protected mode • Memory Limits • Intel processors in real mode use only 1 MB • 640 KB of RAM (conventional memory) is workspace for the OS, applications and data • 384 KB of addresses reserved for system BIOS and RAM and ROM on adapters

10. Finding DOS and Understanding its Strengths and Weaknesses • DOS Weaknesses (continued) • Multitasking Limits • DOS is a single-tasking OS • Hard Drive Limits • DOS only supports hard drives up to 7.8 GB • DOS uses logical drives that are 2 GB or less and within the 7.8 GB total disk space limit • A logical drive is a portion of the physical hard drive with a letter assigned to it

11. Installing DOS • DOS Hardware Requirements • The general DOS hardware requirements for MS-DOS 6.22 and IBM PC-DOS • An IBM or compatible personal computer • 6MB of free hard disk space for the DOS utilities • 512KB of memory

12. Installing DOS • Preparing for DOS Installation • Assure that the computer is a complete system with all the necessary components • Setup program partitions and formats the hard disk • Partition: an area of a physical hard disk that contains one or more logical drives

13. Installing DOS • Partitioning a Hard Disk in MS-DOS • Physical format is done at the factory • Master Boot Record (MBR), the 1st sector on disk, contains the partition table • Partitioning is the first step to prepare a hard disk • Each partition needs a logical format within each logical drive • Partitioning and formatting included in OS installation

14. Installing DOS • Partitioning a Hard Disk in MS-DOS (continued) • FDISK – the partitioning program of MS-DOS • Primary partition has only one logical drive • 2GB is maximum primary partition size in MS-DOS • Extended partition contains one or more logical drives • After partitioning, then format logical drives

15. Installing DOS Step-by-Step 2.01 Installing DOS on a Hard Disk Page 55

16. How the FAT File System Works • FAT File System Components • FAT Table • File allocation table (FAT) – DOS records disk space usage • Cluster – minimum space allocated to a file

17. How the FAT File System Works • FAT File System Components (continued) • FAT12, FAT16, and FAT32 • FAT16 – used on hard disks • FAT32 – available since Windows 95 OEM SR2 • FAT12 – used on floppy disks The number refers to the size of each entry in the FAT table. Length of entry limits the number of entries the FAT table can hold.

18. How the FAT File System Works • FAT File System Components (continued) • How Cluster Size Affects Partitions • FAT16 file system limited to 65,525 clusters • Maximum cluster size 32,768 bytes (32K) • 65,525 x 32,768 = 2GB (maximum partition size supported by the FAT16 file system)

19. How the FAT File System Works • FAT File System Components (continued) • Root Directory and Other Directories • The FAT and the root directory are the two primary components of the FAT file system • DOS uses the FAT to record the location of a file on the disk • A directory is a place where DOS stores information about files, including a referenceto the FAT table • Root directory is the top level directory

20. How the FAT File System Works • FAT File System Components (continued) • Root Directory and Other Directories (continued) • Parent directory contains other directories • Child directory (subdirectory) is within a parent • Each directory entry contains the name of a file or directory, the time and date of its creation or modification, its size, attributes, and beginning cluster information

21. How the FAT File System Works • Using a Directory and the FAT Table to find a File • Directory is like a phone directory for DOS • Finds file name and listing in the directory • Reads the starting cluster number in directory • Looks in the FAT table (like a map of city) for location on disk

22. How the FAT File System Works • DOS file-naming rules: • A file name is up to eight characters, followed by a period, and an extension of up to three characters • A file name and extension can include alpha-numeric characters and a few special characters, but no spaces • Use the wildcard characters asterisk (*) and question mark (?) to locate files and folders

23. How the FAT File System Works • DOS File Types • BAK, BAS, BAT, COM, DOS, EXE, SYS, and TXT are some common file extensions and file types recognized by DOS • Executable Files • COM, EXE, and BAT are the three types of files that can be executed by DOS

24. How the FAT File System Works Step-by-Step 2.02 Creating a Simple Batch File Page 63

25. Read-only Archive System Hidden Volume label Directory How the FAT File System Works • DOS File Attributes • Determine the manner in which DOS handles files

26. How the FAT File System Works • LABEL command • Creates or changes a volume label (name) • If a volume has a label, FORMAT requires the name before reformatting

27. How the FAT File System Works • ATTRIB command • Displays and modifies attributes • Works on read-only, archive, system, and hidden files • Works in both MS-DOS and Windows on FAT and NTFS

28. Working with the DOS Command Prompt • Success at the DOS Prompt • Success means correctly entering commands and getting desired results • Important for working with DOS and other OSs

29. Working with the DOS Command Prompt Step-by-Step 2.03 Using the Online Help in DOS Page 68

30. Working with the DOS Command Prompt • Success at the DOS Prompt (continued) • What is the Correct Syntax? • Syntax is a set of rules for correctly entering a specific command at the command line • The HELP command can be used to find the syntax for a command • COMMAND /?

31. Working with the DOS Command Prompt • Success at the DOS Prompt (continued) • How is a Command Interpreted? • COMMAND.COM interprets the command entered at the prompt • COMMAND.COM loads each command into the memory, and issues additional instructions to the command • COMMAND.COM parses the command entry based on special delimiter characters

32. Working with the DOS Command Prompt • How is a Program Found and Loaded? • COMMAND.COM loads the command named at the beginning of the command line • Must find the actual program code • First checks its own list of internal commands • Then looks for an external command in the current directory, and then in a list called the search path

33. Working with the DOS Command Prompt • Learning to Manage Files and Directories • File management in DOS is centered on the abilities and limits of the FAT file system • It is essential to design a directory structure to save and organize files

34. Working with the DOS Command Prompt • Learning to Manage Files and Directories (continued) • Designing a Directory Structure for File Management • DOS directory/folder structure is hierarchical • Drive | Directory | File Name • TREE command can be used to view the entire directory structure • Store data in a separate directory from applications

35. Working with the DOS Command Prompt • Learning to Manage Files and Directories (continued) • Creating and Removing Directories • MD (Make Directory) will create a directory • CD or CHDIR (Change Directory) allows movement between directories • RD (Remove Directory) deletes an empty directory

36. Working with the DOS Command Prompt • Learning to Manage Files and Directories (continued) • Use File Management Commands • DOS commands are divided into internal commands and external commands • Internal commands are loaded into the memory along with DOS

37. Working with the DOS Command Prompt • Learning to Manage Files and Directories (continued) • Use File management commands (continued): • DIR (Directory), MD, CD, CLS (CLear Screen), COPY, REN (REName), RD, and TYPE are some of the internal commands • XCOPY, DISKCOPY, and DELTREE are often-used external commands

38. DOS Command Function DIR Displays a list of files and folders. DIR /? Lists the available syntax for the DIR command. DIR /P List data one page at a time. CD .. Moves to the parent directory from the present directory. CLS Clears the screen. VER Displays the MS-DOS version. XCOPY Used to copy files and entire directories. COPY Used to copy only files. DELTREE Used to delete an entire directory and its contents. Working with the DOS Command Prompt DOS commands and their functionality

39. Working with the DOS Command Prompt Step-by-Step 2.04 Managing Files and Directories Page 73

40. Understanding the DOS Boot-Up Process and Startup Disks • Why You Should Learn the DOS Bootup Process • Personal computers are multi-purpose devices. • Understanding the normal startup process of the system helps troubleshoot problems that occur during boot-up.

41. Understanding the DOS Boot-Up Process and Startup Disks • DOS system files • IO.SYS handles hardware interaction and loading of drivers • MSDOS.SYS is the kernel of DOS • COMMAND.COM is the command interpreter

42. Understanding the DOS Boot-Up Process and Startup Disks • DOS system files (continued) • DOS Configuration Files • CONFIG.SYS – adds device drivers and modifies DOS settings BUFFERS DOS DEVICE FILES DEVICEHIGH STACKS • AUTOEXEC.BAT batch file loaded during bootup PATH PROMPT SET

43. Understanding the DOS Boot-Up Process and Startup Disks • The DOS Bootup Process • A PC can be booted up by: • Turning on the power switch of the PC (a cold boot) • Using the Ctrl-Alt-Delete key combination to reboot the system (a warm boot)

44. Understanding the DOS Boot-Up Process and Startup Disks • The DOS Bootup Process (continued) • The processor loads a special ROM-based program, called Power-On Self-Test (POST) • POST runs a series of small diagnostic tests on the hardware, and loads the bootstrap loader • The bootstrap loader is a small program in the ROM BIOS

45. Understanding the DOS Boot-Up Process and Startup Disks • The DOS Bootup Process (continued) • On a hard drive, the bootstrap loader looks into the MBR (master boot record) and reads the partition table for the primary active partition • The bootstrap loader loads the boot sector from the logical drive, which, in turn, runs the operating system loading program

46. Understanding the DOS Boot-Up Process and Startup Disks • Creating a DOS Startup Floppy Disk • Using FORMAT to create a startup disk • Using SYS to create a startup disk • Using Windows to create a startup disk

47. Understanding the DOS Boot-Up Process and Startup Disks • Using FORMAT to Create a Startup Disk • The FORMAT command prepares the diskette and places a new root directory and FAT on the disk • The /S switch option places the system files on the diskette

48. Understanding the DOS Boot-Up Process and Startup Disks Step-by-Step 2.05 Create a Startup Floppy Disk Using FORMAT Page 83

49. Understanding the DOS Boot-Up Process and Startup Disks • Using SYS to Create a Startup Disk • The SYS command places the DOS system files on a previously formatted floppy disk • To put the DOS system files on a floppy disk enter sys a:

50. Understanding the DOS Boot-Up Process and Startup Disks • Using Windows to Create a Startup Disk • In Windows 95 and 98 go to Control Panel | Add/Remove Programs | Startup Disk • In Windows XP format a disk from within My Computer or Windows Explorer and select the option to create a MS-DOS startup disk