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 –CP/M used CCP (Console Command Processor) as a command interpreter –BDOS and BIOS – handled system files and I/O

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

DEVELOPMENT HISTORY DateVersion Release August 12, 1981DOS 1.0 – IBM’s release Used Patterson’s 86-DOS May 1982DOS 1.1 IBM’s release of DOS to handle new double- sided drives August 1982DOS 1.25 Microsoft’s own release of DOS 1.1 March 1983DOS 2.0 for IBM’s PC-XT Support 10MB hard drives, 3-internal expansion slots, hierarchical tree structure

DEVELOPMENTS cont. DateVersion Release March 1984DOS 2.1 IBM’s release Handled hardware errors called PCjr 1984DOS 2.11 Microsoft’s release Added international time, date, currency, and keyboard support. 1984DOS 3.0 for IBM’s 16-bit PC-AT system Support 1.2MB diskettes and hard drives over 10MB. Designed by Microsoft to support IBM network hardware November 1984DOS 3.1 Provided better aliasing – made DOS treat directories as drives. Handled network hardware

DEVELOPMENTS cont. DateVersion Release January 1986DOS 3.2 Introduced and provided support of 3-1/2 floppies and 720K disk April 1987DOS 3.3 IBM’s release FDISK can be used to create 32MB or smaller logical drives from extended partitions 1987DOS 3.30 Compaq’s release Support 1.44MB diskettes and multiple 32MB disk partitions November 1987 DOS 3.31 Compaq’s release Support drives greater than 32MB

DateVersion Release July 1988DOS 4.0 IBM’s release Added a DOS Shell interface and support for disk partitions greater than 32MB. Provided support for mouse and graphical interfaces. November 1988DOS Fixed bugs introduced in 4.0 June 1991MS-DOS 5.0 Microsoft’s release Allowed DOS to reside in area above 640K memory. Provided support for loading device drivers. Provided an improved DOS Shell March 1993DOS 6.0 Microsoft’s release Introduced DoubleSpace disk compression DEVELOPMENTS cont.

DateVersion Release November 1993DOS 6.2 Microsoft’s release February 1994DOS 6.21 Microsoft’s release Removed DoubleSpace disk compression June 1994DOS 6.22 Microsoft’s release Introduced “DriveSpace” disk compression April 1995DOS 7.0 IBM’s release August 1995DOS 7.0 Microsoft's release

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 SINGLE TASKING

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

MEMORY MANAGEMENT From:

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

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

DISK MANAGEMENT Solutions to the 32MB hard disk problem 1.DOS 3.3 : FDISK Used to divide large physical memory into smaller logical partitions of 32MB or less 2.Compaq’s DOS 3.31 Extended DOS to hold 32-bit FAT address, thereby allowing logical partitions of.5GB 3.DOS 4.0: Allowed large hard drives greater than 32MB

COMMANDS Internal –Common commands found inside COMMAND.COM, the command interpreter BREAKCALLCD CHCPMKDIRCHDIR CLSCOPYDATE DELDIRECHO ERASEEXITFOR GOTOIFPATH

Commands cont. External –Separate programs outside of COMMAND.COM –Commands are contained their own file –PATH must be set for the commands APPEND.EXEASSIGN.COMATTRIB.EXE BACKUP.EXECHKDSK.EXECOMP.EXE DEBUG.EXEDISKCOMP.COMDISKCOPY.COM DOSKEY.COMPRINT.EXEMORE.EXE

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

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

REFERENCES IBM. “PC DOS 2000.” URL: 3.ibm.com/software/os/dos/dos2000/dos_qa.htmlURL: 3.ibm.com/software/os/dos/dos2000/dos_qa.html Somerson, Paul. DOS Power Tools. New York, NY: Bantam Books. ISBN: Wolverton, Van. Running MS-DOS 20 th Anniversary Edition. Microsoft Press, ISBN: