189 lines
8.0 KiB
Plaintext
189 lines
8.0 KiB
Plaintext
DOS Level 3:
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The world of DOS is a large one. There are many, many commands with optional
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switches in the realm of file management. Fortunately, like most software
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there is a flow and feel to DOS. After you are familiar with the core
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commands, looking up additional ones and figuring out how to use them becomes
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easier. The pattern is a DOS word (DIR, COPY, DEL....) followed by the
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necessary, minimum information to make it go. For example:
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A>DIR B: DIR only needs the drive the directory is
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desired
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A>Copy C:sample.doc B: COPY needs 3 pieces of information - what file
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on which drive is to be copied to which drive
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A>DEL B:Test.EXE DEL needs 2 pieces of information - what file
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on which drive to delete
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SOFTWARE VERSIONS
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-----------------
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Software is labeled with a version number. With each subsequent release of
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the product, the version number increases. The reason for these upgrades are
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to rid "bugs" (problems) within the software, significant product
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improvements, and/or to exploit new hardware advancements. In general,
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anything created on an earlier version of a software will work with a later
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version of the same software. This is known as upward compatibility. The
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reverse is rarely true.
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DOS first hit the market as version 1.0 in 1981. It has gone thru many
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upgrades as new hardware components became available and new DOS features were
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added. Currently DOS 4.X is available. However, most systems are still
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using DOS 3.X versions. For a single user system, any DOS version over 2.1
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is probably adequate. If you are using high density 3.5 inch floppy
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drives, you will need at least DOS 3.X.
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When application software is purchased, DOS version requirements are noted on
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the package as well as RAM requirements.
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FILE ALLOCATION TABLE
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---------------------
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As was discussed earlier formatting a new floppy disk prior to use,
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electronically superimposes a grid system on the disk. Each grid intersection
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(sector) is numbered. The location of files pieces on a disk are noted in a
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File Allocation Table (FAT) on each disk. When a file is copied to a disk,
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the FAT is checked for available sector locations.
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The FAT is like an index to the location of file pieces on the disk. File
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portions DO NOT have to be in adjacent sectors. As a disk repeatedly has new
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files copied to it and old files deleted, files become fragmented - portions
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of the file exist in non-adjacent sectors. This situation is referred to
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as non-contiguous sectors. Data integrity is not affected by this situation,
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but the speed in which data can be retrieved is. There are many third party
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products to "defragment" a disk. If the programs you will be using are disk
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intensive - like accounting or database management, you will notice a slowing
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of program execution over time as files become fragmented.
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When a file is deleted from a disk, the contents are not wiped from the
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sectors, rather the file name is removed from the FAT and the associated
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sectors are now simply declared available for new data. This is important to
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understand because deleted files are actually still on the disk but their
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locations are now not considered off limits. Again, many third party software
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products are available to undelete these files.
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If you do delete a file, try not to use the disk until the proper utility
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software is available to reverse the deletion. With more use, you are running
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the risk that the next file that is copied to the disk will occupy the
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sectors of file you wish to undelete. If that should happen, you will not be
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able to undelete the "old" file.
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Some popular third party utility tools to defragment a disk and allow
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undeletion include PC TOOLS, NORTON UTILITIES, MACE UTILITIES, VOPT DISK
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OPTIMIZER.
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BATCH FILES
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-----------
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Batch files are a DOS tool that allow you to automatically execute 1 or more
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DOS commands sequentially. A more detailed explanation can be found under
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Hard Disk Dos sections.
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For example, you are tired of changing default drives, subdirectories and
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typing the word LOTUS each time you wish to enter into the LOTUS 123
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spreadsheet program. The 3 steps required are:
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A>C:
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C>cd\lotus
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C>lotus
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These steps can be combined with a single BATCH file called LOT.BAT.
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To build:
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C>copy con:lot.bat --- Begin creating a file called lot.bat
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C:
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cd\lotus
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lotus
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<F6> --- End building and save to disk by
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pressing the <F6> function key
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Now, each time LOT is entered at the DOS prompt, the commands within the
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LOT.BAT file are automatically executed sequentially.
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C>lot
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REDIRECTION
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-----------
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Redirection refers to having input or output come or go to devices other than
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the standards of Keyboard (Input) and Monitor (output). In DOS we expect to
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enter commands from the Keyboard and have the results displayed on the
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Monitor.
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A>DIR --- Gives a directory of the A drive disk on the
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monitor
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A>DIR >PRN --- PRN means to send the results of this command
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to the printer
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A>DIR >LIST.TXT --- Now the output of this command is put into a
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file on the A disk called LIST.TXT (any
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filename could have been used)
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The greater than sign ( > ) used above was to REDIRECT the output to a
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Printer and a Disk File rather than the default output device; the monitor.
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This is useful for getting a hard copy print-out of a particular disk's
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contents.
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PIPING - FILTERS
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----------------
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Piping is a way of telling DOS to transfer the output from one command to be
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the input for another command. Piping is a form of redirection except DOS
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will create a temporary file on a disk to accomplish the task.
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Piping usually involves the use of special commands, termed Filters, to accept
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data, do something with it, and then pass it to the next step. There are 3
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standard filters used by DOS in piping:
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FIND - used to search a file directory for a specified string of text
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MORE - used to display one 1 screen of output at a time
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SORT - used to sort disk filenames
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The symbol used by DOS to indicate a Piping operation is the vertical bar (|).
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Examples:
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A>DIR |sort --- Will display on the monitor the list of files
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on the A disk, BUT in filename alphabetic order.
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A>DIR |sort/+10 --- Will display on the monitor the list of files
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on the A disk, BUT by alphabetic order of the
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filename extensions. Extensions are 10
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characters from the left on the screen during a
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DIR.
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A>DIR |sort >prn -- Same as the 1st example except the results of
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this command will be printed out.
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A>DIR |sort >SAM.D - Same as the 1st example except the results of
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this command will be saved in a file on the disk
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called SAM.D
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A>DIR |sort |more -- Will display in sorted order one screen at a time
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A>DIR |find "05-14-89" -- Will display a list of files that were last
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changed on May 14, 1989
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A>DIR |find "SALES" -- Will display a list of files that have the
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word SALES in the file name
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***** END OF FILE: Press <ESC> to return to Main Menu *****
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