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Chapter 6. Disk Operating System. Hardware. ROM BIOS. Operating System. Internal Commands External Commands. Memory I/O Device’s. Applications. Video Area. 640 K. Program Memory. Command Resident. MS-DOS. IO System. Interrupt Handler. 0000.

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chapter 6

Chapter 6

Disk Operating System

slide2

Hardware

ROM BIOS

Operating System

Internal Commands

External Commands

Memory

I/O Device’s

Applications

slide3

Video Area

640 K

Program Memory

Command Resident

MS-DOS

IO System

Interrupt Handler

0000

Figure 2 Memory Map of 8088 Processor

slide7

C:DOS (ROOT dir)

Chicago dir Atlanta dir Portland dir

Payroll Inventory

Payroll Inventory

Payroll Inventory

Files Files Files Files Files Files

path statement
Path statement
  • Absolute pathname
  • C:\US\sales\salesreps\smith
  • Relative pathname
  • CD \smith
  • “Program not found”
slide9
8.3

File Specification A:\DIRNAME\FILENAME.EXT

Drive location

Directory location

File Name

Can be up to 8 eight characters

The following characters are not allowed:

. ” / \ [ ] < > + = ; ‘ Spacebar

Extension

commands
Commands
  • Name Options Parameters
  • Keyword Drive Options
  • Keyword Source file File switches
  • Do what? To who? How?
command essentials
Command Essentials
  • You must enter words shown in capital letters y).
  • You must supply any items shown in italic letters
  • Items in square brackets [] are optional.
  • Items separated by a bar ( | ) means you can enter one of the other ( Example OFF | ON )
  • An Ellipsis (…) indicates you can repeat as many time as you want.
  • You must include all punctuation, except square brackets and vertical bars.
global filename characters
Global Filename Characters
  • ? = can be any character
  • * = any character can occupy that position and all remaining positions
  • DIR A:INPUT.??? Or DIR A:INPUT.*
  • ******WARNING*******
  • DELETE C:*.*
  • ******WARNING*******
batch commands
Batch Commands
  • ECHO,FOR,GOTO,IF,PAUSE,REM
  • A batch file is a file containing 1 or more commands that DOS executes. ext = .bat
  • ECHO ON
  • REM This is an example of a batch cmd.
  • Copy C:prog1.exe to C:prog2.exe
  • DIR
  • Autoexec.bat = start program at DOS start
redirection
Redirection
  • DIR >PRN Sends cmd to printer
  • DIR >catalog Sends cmd to filename
  • MYPROG <INPUT.TXT
  • DIR >> filename appends to file
piping filters
Piping & Filters
  • Filters = SORT, FIND,MORE
  • DIR|SORT>FILE
  • SORT <MYFILE >RESULT
  • TYPE MYFILE|MORE
slide16
Help /?
  • Command Summary C:>Help
  • Help command-name (C:>help copy)
  • Copy /?
physical structure of a diskette
Physical Structure of a Diskette
  • Formatting
    • concentric circles called tracks
    • pie-shaped wedges called sectors
  • Data is written to the tracks as bits,0’s and 1’s
    • bits become magnetized spots on the disk
    • spacing prevents one spot from affecting other spots
  • Read/write heads
    • above and below the diskette move in unison
  • Diskette made up of Mylar
    • covered with either cobalt oxide or iron oxide to hold magnetic charge
    • Formatting writes the division symbol ÷ F6 1111 0110 to each track
logical structure of a diskette
Logical Structure of a Diskette
  • The BIOS manages the disk in sectors, physical terms
    • a sector holds 512 bytes of data
  • The OS manages the disk in clusters, logical terms
    • A cluster is defined as the smallest unit of data that can be read from or written to at one time
    • File allocation unit (FAT)
    • One cluster equals the amount of storage space per two sectors, top and bottom of the diskette

512 bytes X 2 = 1024 (one cluster, double-density 3.5” diskette )

80 X 9 = 720 (one side of diskette in sectors, the whole diskette in terms of clusters)

1024 X 720 = 737,280

slide21

Diskette size

Tracks per side

Number of sectors per tracks

Capacity

5.25" Single side

SD8

40

8

40 X 8 X 512 bytes = 160 KB

5.25" Double side

DD9

40

9

2 X 40 X 9 X 512 bytes = 360 KB

5.25" Double side High Density

DQ15

80

15

2 X 80 X 15 X 512 bytes = 1.2 MB

3.5" DD

DQ9

80

9

2 X 80 X 9 X 512 bytes = 720 KB

3.5" HD

DQ18

80

18

2 X 80 X 18 X 512 bytes = 1.44 MB

3.5" XD

( IBM only)

DG36

80

36

2 X 80 X 36 X 512 bytes = 2.88 MB

The Standard PC Diskette Configuration:

Diskette drives turn at 300 RPM. That results in an average search time (½ revolution) of 100 ms.

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