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MS-DOS/PC-DOS

MS-DOS/PC-DOS. by: Temitope Akanni CS550: Operating Systems Fall 2003. CP/M. Created by Gary Kildall Control Program for Microcomputers was used to run floppy disk drive of IMSAI 8080 Licensed from Digital Research Features from CP/M COM formats

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MS-DOS/PC-DOS

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  1. MS-DOS/PC-DOS by: Temitope Akanni CS550: Operating Systems Fall 2003

  2. CP/M • Created by Gary Kildall • Control Program for Microcomputers was used to run floppy disk drive of IMSAI 8080 • Licensed from Digital Research • Features from CP/M • COM formats • CP/M used CCP (Console Command Processor) as a command interpreter • BDOS and BIOS – handled system files and I/O

  3. QDOS • Quick and Dirty Operating System, written by Tim Patterson of Seattle Computer Products to take advantage of the 16-bit Intel 8086 board • QDOS became 86-DOS and then DOS • Features from QDOS • C:> prompt • 8 character file names with 3 character extensions

  4. DEVELOPMENT HISTORY

  5. DEVELOPMENTS cont.

  6. DEVELOPMENTS cont.

  7. DEVELOPMENTS cont.

  8. DEVELOPMENTS cont.

  9. SINGLE TASKING • DOS is a single-tasking OS but DOS 2.0 allowed users to print out files while working on another. • OS/2 provided a multitasking environment. TEMPORARY ENVIRONMENT • DOS allows the user to specify a temporary command processor (child process) with its own environment. Change in child environment is not reflected in the parent. • C:> cmd /E:512

  10. FILE MANAGEMENT • Uses a multi-level hierarchical directory structure • FAT file contains the addresses of file clusters to build data • Some hard disks contain two copies of the FAT file, which are updated when data changes in a file

  11. MEMORY MANAGEMENT From: http://www.frick-cpa.com/dos/DOS_Memory_1.asp

  12. MEMORY cont. • Conventional Memory: User Memory from 0– 640Kb • Expanded Memory: below 1024Kb of memory • Extended Memory: 1024Kb or 1MB and above • High Memory Area (HMA): The first 64Kb block of memory in EMA • Upper Memory (UMA): Memory located between 640K and 1024K

  13. DISK DILEMMA • Problem: Designers must decide the size of FAT chart • Standard diskette held: 160K • IBM PC came with 16K of RAM • Solution: Give FAT a maximum of 16-bit address • Largest table could have 64K entries • 64K entries * 512bytes/sector = 32MB (Maximum size of hard disk) • Created problem in accessing larger disks drives

  14. DISK MANAGEMENT • Solutions to the 32MB hard disk problem • DOS 3.3 : FDISK • Used to divide large physical memory into smaller logical partitions of 32MB or less • Compaq’s DOS 3.31 • Extended DOS to hold 32-bit FAT address, thereby allowing logical partitions of .5GB • DOS 4.0: • Allowed large hard drives greater than 32MB

  15. COMMANDS • Internal • Common commands found inside COMMAND.COM, the command interpreter

  16. Commands cont. • External • Separate programs outside of COMMAND.COM • Commands are contained their own file • PATH must be set for the commands

  17. Internal/External: A Brief Exercise • To check if a command is internal/external • type: set path= • format /? copy /? – these are internal commands Example of an external command: • D:\>doskey /? • 'doskey' is not recognized as an internal or external command, operable program or batch file. • Start another command session • Don’t set the path to null • Type doskey at the prompt • Nothing happened, but the doskey executable (DOSKEY.COM) was found and is running

  18. FUTURE OF DOS • Windows OSs and IBM OS/2 Warp can run DOS applications but do not rely on it • IBM has a PC-DOS 2000 • Caldera has an extended version of DOS call DR-OpenDOS • DOS will fizzle out but not for another couple of years

  19. REFERENCES IBM. “PC DOS 2000.” URL:http://www-3.ibm.com/software/os/dos/dos2000/dos_qa.html Somerson, Paul. DOS Power Tools. New York, NY: Bantam Books. ISBN: 0-553-35464-7 Wolverton, Van. Running MS-DOS 20th Anniversary Edition. Microsoft Press, 2002. ISBN: 0-7356-1812-7.

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