Hard Disk Management - Level 1:
DOS Disk Operating System (Director Of Services) — Master control program for the flow of information within a PC. One of its primary functions is to oversee all disk activities - reading/writing information from/to a disk, and loading/executing programs. It controls (links) all hardware devices so they may communicate with one another including:
Floppy Drives: 5.25", 3.5"
Hard Drives: 10mb, 20mb, .....
Ram Disk: Simulates a disk drive from within RAM
Laser Disk: "CD's" for computers
Tape Storage Device: Backup system typically using cassette type
tapes
PLUS, Screen, Keyboard, Printer, Modem, Mouse, …
As if this wasn't enough, this modest software called DOS also keeps track of the current time and date, and the usage of all memory locations within RAM.
Once DOS has been properly BOOTed, you will see the familiar "DOS Prompt":
A>
This says: 1. DOS has been properly installed
2. "A" is the default drive
3. DOS is awaiting your next command
HARD DISK DRIVES
Also called Hard Drive, Hard Cards, Fixed Disk Drives. Hard Drives are essentially large floppies housed within the computer. They are much faster, much higher capacity, and less likely to fail due to the safe environment from within which they operate.
Hard Disk cost is related to its capacity and it Access Time. Access Time is the amount of time it take the disk to locate a random piece of information. Access Time is measured in milliseconds (ms-millionths of a second). A fast one would be 28ms, a slow one 65ms.
DOS REALITIES
There are three types of FILES that may be successfully "executed" from the DOS Prompt:
1. *.EXE Commands ("EXECUTE" Program files Lotus, dBASE,....)
2. *.COM Commands ("COMMAND" Program files Lotus, dBASE,....)
3. *.BAT ("BATCH" Custom programs )
To successfully execute one of the *.EXE, *.COM, or *.BAT command files, the file itself must be either:
1. In the Current directory
2. Within a directory that is part of the DOS "PATH" command
Batch (.BAT) files are the only executable files you can write using a simple word processor, or DOS's built in Line Editor (EDLIN) - more later.
BOOTING (or Bootstrap) To load and execute the Disk Operating System-DOS
This term comes from the phrase "pull yourself up by your own bootstraps". This happens within a PC when it is turned on. Actually, a built-in program (ROM) is executed, then a couple of "hidden" files from the ROOT directory (hard drive) or DOS Disk (floppy disk), then COMMAND.COM (DOS internal command interpreter) followed by the Optional CONFIG.SYS and AUTOEXEC.BAT files.
COMMAND.COM: Must by loaded for DOS to operate properly, it contains
the Internal DOS commands - those used most often: Copy,
Dir, Del, etc. The remainder of files on the DOS disk
are called External Files (DISKCOPY, CHKDSK,...). To
utilized one of these commands, the DOS disk must be
accessible.
CONFIG.SYS: Optional. If it is located on the Disk that you are
BOOTing from, DOS will "open" it and read and interpret a
list of system configuration commands. This is a ASCII
text file which can be created by any text editor.
Configuration commands include: FILES, BUFFERS,
DEVICE,...
AUTOEXEC.BAT: Optional. An ASCII text file. "Opened" and read after
CONFIG.SYS, IF it exists on the BOOT disk. A "batch"
file. A set of DOS commands and other special commands.
SOME FREQUENTLY USED DOS COMMANDS WITHIN A HARD DISK ENVIRONMENT
A Hard Disk is just like a floppy. However, due to its size additional file management commands are needed. The following can also be used on floppy disks, but they are most common in Hard Drive Environments.
INTERNAL ³ EXTERNAL (Insert DOS in Drive A)
³
MD ³ CHKDSK CD ³ BACKUP RD ³ RESTORE PROMPT ³ SUBST PATH ³ TREE
– Internal DOS Commands - MD - Make a directory (see below) CD - Change to a directory (see below) RD - Remove a directory - must be rid of files first (see below) PROMPT $p$g - Changes the way the DOS prompt is display. $p$g insures that the current directory is shown at the prompt. Very useful. Usually "set" in the AUTOEXEC.bat file (see below) PATH=c:\DOS;c:\BATCH;c:\UTILITY Sets up a command (*.EXE, *.COM, *.BAT) search path in the DOS environment. When a command is issued from the DOS prompt, it first looks in the directory you are currently in, then looks in each directory noted on this path. Usually this command is built into the AUTOEXEC.bat file (see below) – External DOS Commands -
CHKDSK C:\*.* /F
Checks the integrity of disk files - the level of fragmentation of files. Indicates the number of files and amount of free storage space remaining on the disk in drive A. It also indicates the amount of RAM storage. If any lost clusters are found (data without a home), they can be converted to *.CHK files so you can delete them to free up the disk space.
SUBST E: c:\LOTUS\123FILES - Assigns a 1-letter drive ID to a
directory path
SUBST E: /D - Cancel previous designation
TREE /F - Displays a list of files and directories on the disk.
/F - more detail - all files, all directories
BACKUP (see below)
RESTORE (see below)
DIRECTORIES
As previous mentioned, a hard disk is essentially a large floppy disk. However, it offers some distinct advantages:
Is much larger
Stays inside the machine
Operates (transfers data) at a much higher rate (5-10x)
Because a Hard Disk is so much larger than a floppy, we use an additional file organization tool called SUBDIRECTORIES.
If a floppy is like a filing drawer, than a Hard Drive is like a wall of file drawers, each drawer call a SUBDIRECTORY.
DOS lets you organize files using tree-structured directories rather than a single directory. In other words, since a 20 meg (20,000,000 byte) capacity hard drive can contain approximately 60 floppy disks worth of files, an additional organization tool is needed. The creation of SUBDIRECTORIES allows us to subdivide a disk to contain related files. It's as if we have many file cabinets available to store our files rather than a single giant one.
DOS permits up to 112 files on a floppy disk. However, with that many it is a labor to examine via a DIR and it also slows DOS's file access and retrieval.
ROOT DIRECTORY - Main directory - it provides support for all the SUBDIRECTORIES. It contains all the SUBDIRECTORIES.
Each SUBDIRECTORY can contain files as well as other SUBDIRECTORIES. These other Subdirectories could be thought of as SUB-SUBDIRECTORIES.
To use a file in a different drive we have specified the drive and filename (B:Filename.ext). Similarly, if we want to access a file in a SUBDIRECTORY we specify a PATH, OR make that SUBDIRECTORY the "current" one.
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PATH: A PATH specifies the names of the directories that DOS must go through from the ROOT DIRECTORY to get to the file. The directories are separated by a forward slash ( \ ). (NOT the same as the DOS PATH
command noted above)
EX: C:\123FILES\PROJECTX\BUDGET.WK1
C:\ Root Directory
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ÃÄ 123FILES Lotus files Subdirectory
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ÀÄÄÂÄÄ PROJECTX Sub-Subdirectory containing all "PROJECTX"
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ÀÄÄÄÄÄ BUDGET.WK1 A specific Lotus file called BUDGET within
the PROJECTX Subdirectory
DOS & SUBDIRECTORIES - there are only 3 key commands in dealing with Subdirectories: MD, CD, and RD
TO MAKE A SUBDIRECTORY
MD dirspec - Internal - to MaKe a DIRectory -dirspec is the name of
the subdirectory or its PATH
EX: C>MD 123FILES <ENTER> - This creates a subdirectory
called 123FILES
- Naming a SUBDIRECTORY follows the same rules for
file naming, except extensions are not used
- You can created unlimited number of SUBDIRECTORIES
- Identical Filenames can exist in different SUBs
(Remember, 2 files with identical filenames CANNOT coexist
in the same SUBDIRECTORY)
TO CHANGE THE "CURRENT" SUBDIRECTORY
The computer can only have 1 "file drawer" open at a time - thus this is called the current directory. Unless instructed otherwise, the computer will assume all files sought and sent will go into this current subdirectory.
CD\dirspec - to Change the "current" Directory
- EX: C>CD\LOTUS <ENTER> - This makes a subdirectory
called LOTUS the current one TO REMOVE/ERASE A SUBDIRECTORY
1. First make this directory the current one C>cd/dirspec
2. DELETE all the files within this directory
C>DEL *.*
It will ask if you are sure - Y
3. Go to the ROOT DIRECTORY C>cd\
4. RD dirspec - Reove Directory
C>RD dirspec
* END OF FILE: Press <ESC> to return to Main Menu *