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████████████████████████████████████████████████████████████████ DOS FOR BEGINNERS - A LOW STRESS INTRODUCTION ████████████████████████████████████████████████████████████████ DOS stands for disk operating system. DOS is the software program which controls the primary input and output of your computer while you use an application program such as your word processor or database. Learning about DOS isn't that difficult after all. It seems that beginners live in fear of DOS. A better way to do things is to imagine that DOS is a kitchen of cooking tools and helpful chefs waiting for your instructions on what to fix for lunch. Here's the point of the analogy: you've got to be a little comfortable in the kitchen to live (no food - no you!) Same thing with DOS. Learn just a little and you can survive with the computer. But just as with the kitchen, a steady diet of peanut butter sandwiches may keep you alive (i.e., passing familiarity with only 4 or 5 DOS commands) but as with the kitchen, life is more flavorful eating a variety of things like fish, salad and dessert (i.e., a richer DOS diet of varying commands.) DOS or the disk operating system controls the flow of data to and from the screen, keyboard, disk drives, printers and of course the integrated circuit RAM (random access memory) chips wherein data is stored and processed. In as sense, DOS is the "verbal interpreter" through which your program (e.g., word processor) talks to the raw hardware. Somewhat like a person in a foreign land who needs a language interpreter. Over the years DOS has been produced in a variety of versions. New commands and capabilities have been added and different versions for a variety of machines have evolved. Thus you might bump into a version of DOS for a true IBM machine and a version of DOS for a machine manufactured by Tandy. PC-DOS is a version of the more general MS-DOS developed for 16-bit computers using the Intel-manufactured line of CPU microprocessor chips. DOS is a software program having MANY parts! It consists of one (or more) disk(s) having an input/output system, a command processor, and several utilities. Don't worry about all of this right now, just be aware that DOS has several parts. The utilities are small software program files which are found on your DOS disk. These utility files perform helpful tasks such as formatting a disk or checking it for errors. Since they are a part of DOS, they live on the same disk but are not needed all of the time (e.g., you may need to format disks only once or twice a week and thus occasionally use FORMAT.COM which lives on your DOS disk.) Thus these EXTERNAL disk-based utility programs live in the computer's RAM (random access memory) chips TEMPORARILLY while in use and usually are kept on the disk until needed. They are EXTERNAL commands. Other commands live inside RAM memory because they are used frequently and are INTERNAL DOS commands. The file FORMAT.COM is an example of an EXTERNAL COMMAND. An example of an INTERNAL COMMAND would be DIR. We will talk about these and other DOS commands later in this tutorial. Don't worry about this distinction now. Just remember that there are two basic types of DOS commands which will start to become more apparent as we delve deeper into DOS magic. ████████████████████████████████████████████████████████████████ USING DOS THE EASY WAY DOS SHELLS AREN'T FOUND AT THE SEASHORE! ████████████████████████████████████████████████████████████████ Before we start our main DOS tutorial a brief alternative: There is always an easier way to do anything - given enough time and ingenuity. If DOS commands and structure are not interesting or you don't have the time to learn DOS, there exist programs called DOS SHELLS which essentially provide DOS access for routine things like moving and copying files; these menu programs hide the DOS commands behind a series of "point and select" choices and options a little bit like the point and shoot menus you are using with PC-LEARN! The typical DOS shell is a package which surrounds DOS (like a shell, hence the name) and allows you to perform the most common DOS functions by pressing only one or two keys or moving a highlighted arrow. Very appealing for beginners! This may be all the DOS control most people need . . . This is a bit like using a cash machine at the bank. If you need to take money out of the machine, you insert your card, key in a password and press a few different choice buttons. DOS SHELLS provide a screen of DOS command CHOICES, allowing you to point the arrow or cursor at the task you want done. You see a menu of choices instead of a cryptic C> prompt. The tradeoff is that you may miss out some of the more subtle operations that direct contact with DOS can provide, but then sometimes it is easier to get the task accomplished without fancy sidetracking and confusion. There are two flavors of DOS shells: memory resident (stay put in the computer memory) - which are always available whether the DOS shell disk is in the machine or not. The second type, non- resident shells live on the disk and must be present in the disk drive to be used. Non resident DOS shells do not use active RAM memory continuously and thus free more memory space for your main program. Some DOS shells also have added features: security passwords and macros (the capability to cause one key or key combination to instantly type a long string of commands!) DOS shells are a good "beginners crutch" to let you work with the computer and its DOS operating system without having to learn the DOS commands and their somewhat arcane syntax. Some practical and easy DOS shell packages include: Still River Shell, DOS2ools, PC Tools, Powermenu, Automenu, Dirmagic and Directory Freedom. If you would like a shareware copy of Directory Freedom with colorful menus of choices which works and looks a little like PC-LEARN and allows you to issue many DOS commands with simple menus, contact the author of this package. If you are beginner and don't want to be troubled learning DOS, then a shell program is the easiest way to use the PC. ████████████████████████████████████████████████████████████████ USING DOS - THE NUTS AND BOLTS ████████████████████████████████████████████████████████████████ Next let's jump into our main DOS tutorial, for those intersted. Remember, there are TWO ways to use DOS. Directly at the prompt using what is termed a COMMAND LINE. This is the detailed method we will study in a paragraph or so. A second way is to use a DOS SHELL to manage files and other data, as we discussed previously. The following examples are best practiced at the DOS prompt A> or C> rather than within this tutorial. You might wish to print this tutorial and then practice the examples with your computer displaying a true DOS command line such as C> To print this tutorial, use the print file option from the main PC-LEARN menu. Now let's begin the tutorial: When you first turn on the computer with only the DOS disk in place, assuming some automatic startup software or menu program has not been installed, you will see the lonesome a> prompt or maybe c> prompt if you have a hard drive. The DEFAULT drive is the disk drive in which DOS will search for a program or file if no other specification to another drive is given. The prompt tells you which drive is the default drive at the moment. DOS can specify up to 63 drive names (not just a, b and c!) If a> is on the screen it is the DOS prompt and in this case the A: drive is the DEFAULT floppy drive which will be searched for information if you issue a command and ask DOS to execute it. You can CHANGE the default drive simply. Let's try switching drives. If you see a> try the following example: (example) b: <press enter or return key> The result on screen is now b> The computer now pays attention to b: (b drive). Hopefully there is a disk in b: drive or DOS gets confused and will give you an error message. If you have a hard drive (which is usually the c: drive,) you can try switching back and forth between your a: drive and c: in a similar manner. Try switching around between drives, go back and forth a few times. Switching drives is a VERY IMPORTANT SKILL, SINCE DOS PAYS ATTENTION TO THE DEFAULT DRIVE WHOSE LETTER IS DISPLAYED! Next let's try some other simple DOS commands. Try these . . . (example) a>ver <then press enter key> (example) a>time <then press enter key> (example) a>date <then press enter key> In the above examples, you first asked DOS to tell you what version of DOS you are using then a request to tell you the time and date. Get the idea? Type in a word or phrase and something happens. But just what are the words and phrases? Let's jump deeper . . . (example) a>dir/p <enter> You get a listing of files in the drive (hopefully a disk is in the drive.) Notice that we added /p to the end of a command. P is shorthand for "pause after each screenful." The DIR command means directory (a list of files or programs on the disk.) You can modify a basic DOS command like DIR with additional COMMAND SWITCHES and ARGUMENTS (e.g., /p) which are fancy words which simply imply modifications to a basic DOS command. Try this . . . (example) a>dir/w <enter> /w means "wide screen" (example) a>dir a: <enter> list a: drive contents (example) a>dir b: <enter> list b: drive contents You will notice that the DOS prompt stays with or in the default drive you started from but can examine another drive directory then COME BACK to the default drive from where you started. Another way of explaining this is that you can switch back and forth between drives (typing a: or b:) and ask for directories OR you can stay in a drive and ask DOS to look at either a: or b: independently of the default drive. Flexibility! Tip: A REMINDER: DOS is a computer operating system. Many of its commands once loaded stay inside the machine. As long as the power is on, these commands stay resident (stay put) and are called INTERNAL commands. DIR is an example of an INTERNAL COMMAND - it lives inside the computer once DOS is loaded. EXTERNAL COMMANDS however only live on the DOS disk and can be copied to other disks (example: SORT.COM). They load TEMPORARILY into the computer memory, do their job and then are gone. EXTERNAL DOS COMMANDS MUST HAVE A DOS DISK (OR COPY) of that command in a disk drive when you need them. While we are concentrating on DOS at the moment it is important to understand that DOS is only an operating system. DOS is the first step. The second step for most people is to use higher level (more useful) programs such as word processors, accounting systems, games (or whatever). These higher level APPLICATION programs are started by entering a simple word or instruction at the DOS prompt. For example, if you purchased a word processing disk it might instruct you to insert that special disk into the computer and type: a>start (then press enter key) The point is that DOS is a program which itself allows other more useful programs to be loaded into the PC and operated. TIME TO JUMP TO LIGHTSPEED! The listing which follows is a portion of the most useful DOS commands with examples and clarification tips. Your DOS manual contains many more. ██ DIR ██ (Internal command) lists a table of disk file contents. Use this command to view a disk volume label, all filenames, sizes of files in bytes, the date, time of file creation and amount of space left for storage on the disk. A disk for IBM PCs clones hold about 360,000 bytes or computer "words." DIR/W lists columns in "wide screen mode" DIR/P lists in "pause" mode (one screen at a time). You can also locate or find certain files. Example: a>dir letter.bak Example: c>dir rll.wks. You can switch and view another directory. Example: c>dir b: Example a>dir c: When you issue the DIR command your screen will produce a listing similar to this assuming you have a disk in the floppy drive: COMMAND COM 16037 2-15-84 3:55p ANSI SYS 1632 6-26-84 5:15p ASSIGN EXE 1386 5-22-84 3:42p AUTOEXEC BAT 40 3-26-87 6:32a BACKUP COM 11855 12-11-84 1:02p CHKDSK COM 6468 10-19-83 7:51p DEBUG COM 12223 10-19-83 7:52p DEVCNFG COM 4621 9-18-85 7:01p DISKCOMP COM 2088 9-12-85 4:41p DISKCOPY COM 1409 10-19-83 7:51p DISKSHIP EXE 2376 8-29-85 11:08a In the above partial screen listing, the first word in each line is the filename. The second word is the file extension. (Example: the first file is actually named COMMAND.COM not COMMAND COM ). The next number is the byte count or file size (i.e., how many computer words or bytes make up the file). The next item is the date of file creation. The final item is the time of file creation. This is very useful as you start to build up a collection of files! Which one is the latest and when did I write that financial report are common questions and good reasons why a date and time of file creation is important to both DOS and you. Tip: FILE HANDLING with the DIR command and DOS. On the screen a directory listing might show a file as PC-LEARN WKS But the true syntax to DOS is always PC-LEARN.WKS The point is that you need a dot between the filename (first part) and the extension of the file (second part) or DOS cannot handle the file properly. FILENAMES. There is a meaning to life, as they say. Filenames have meaning. The clue as to the use of a file usually resides in its three character file extension. Files can be typed in upper or lower case, DOS doesn't care! Names longer than eight letters will be shortened automatically to eight letters. File extensions longer than three letters will be shortened to three letters. The file name frequently gives a clue as to the nature of the file. The file extension or endname tells WHAT KIND of file it might be. Acceptable characters which can be used to make up a file name are: A-Z 0-9 $#&@!()-{}'`_~ Unacceptable characters which CANNOT be used in a filename are: |<>\^+=?/[]";,* (and also) Control characters and the space Examples of filenames: 123.EXE The program 123, an "executable" file. Think of as a program that can be started and "run" to do something. GO.BAT A Batch file (bat). Like an exe file. Contains plain english DOS commands and can be viewed with the DOS "type" command. VIEW.COM Unknown file, but a "command" type, similar to an exe file. 783.WKS A worksheet file from lotus possibly from July of 1983 (7/83) README.TXT Probably a text file in plain english. Can be read and viewed with the DOS command: TYPE (discussed below.) XVC.DBF Unknown file, but we might guess a dBase database program database file. CONFIG.SYS A PC system file. Helps "configure" your computer for specific hookups, and equipment. If you type A>ZIGZAG (then press enter key) DOS will look for: ZIGZAG.COM or ZIGZAG.EXE or ZIGZAG.BAT. As we illustrated in the directory listing above, the first (ZIZAG.COM) is a COMMAND file or program which can be run to do something. The second is an executable file. And, the third is a batch file (see the batch file tutorial). Both .COM and .EXE files can execute as programs. The difference between the two relates to how memory is allocated. COM files when loaded into memory are exact mirror images of their structure on disk. EXE files are usually larger programs which use extensive chunks of RAM memory and are not exact images of their disk counterpart. An arcane but interesting distinction. A DOS command has a unique command syntax just like we humans have rules of grammar. A DOS command has a mandatory part and some DOS commands have an optional part. For example, DIR C:pathname\filename.ext/w/p is the complete syntax for the DOS DIR command we used above, BUT only DIR is mandatory. We will explain pathnames and directories in a later tutorial. For now just realize that DOS commands have a central or mandatory command and additional "refinements" or options with little / and \ bars to refine the command. / is a slash. \ is called a backslash. You don't need to use the refinements, but they help as you grow in proficiency. FILE HANDLING LIES! DOS is quite honest for the most part. When you ask for a directory listing of files on a disk you usually get it. EXCEPT for two small lies! On the main DOS disk are two files which cannot be seen on the directory (hidden) but are there: IBMBIO.COM and IBMDOS.COM. These files are the core of the operating system. The designers of DOS hid them for two reasons 1) copyright concerns 2) protection from accidental erasure. But the biggest problem is that these two special files will not copy to disks in the normal manner (see our copy discussion below). These two files can only be copied with the SYS command or DISKCOPY command (also below). Without these two files a disk cannot boot or startup the computer. When you copy a DOS disk the COPY command copies almost everything (except IBMBIO and IBMDOS.) The DISKCOPY command copies everything. You only need IBMBIO.COM and IBMDOS.COM to start the computer. IBMBIO.COM and IBMDOS.COM do not have to be on every disk - only those disks which start the computer. Tip: STOP! Not a formal DOS command, but if you need to stop something in progress, (copying, listing) do this: If a directory is scrolling endlessly down the screen, hit control key AND the S key held together. This stops things until you want to continue (hit any key). To stop a DOS operation altogether, use control key and C key together. Easy way to remember: control-C means crash. control-S means stop. This will not always work within every program (e.g., inside lotus 1-2-3) but it does work within DOS. ██ TYPE ██ (internal) displays or "types" the contents of a file on your monitor. Use type for a glimpse into files. Only text files (also known as ASCII files) will read in english. Other files (com or exe) will show gibberish since they are in computer code. Hit CTRL-Z to stop (control and Z keys). Hit Ctrl-S (control and S key) to pause and any key to restart. Example: a>type readme.1st (sends output to screen) Example: b>type readme.1st>prn (sends output to printer) ██ ? and * ██ DOS can use "wildcards" in many operations (? *). Simply stated, these wildcards take the place of letters and numbers. Use the question mark as any SINGLE character. Use the * as any GROUP of ANY LENGTH of characters. Think of them as shortcuts to get the job done! Very powerful and useful! Frequently used with the COPY and DEL commands which are discussed in a few paragraphs. Example: c>dir a:*.wks Means provide a directory listing of any files on the a: drive ending in WKS and beginning with ANY characters of ANY length from 1 to eight digits. Files such as MY.WKS or NUMBERS.WKS or NAMES.WKS would fit this description. Example: b>copy ???.dat a: Means copy any files to a: drive ending in DAT and having any characters in the filename AND ONLY filenames exactly three digits long. The often used *.* means ANY FILE NAME and ANY extension regardless of length. For instance: Example: c>copy *.* a: (means copy ALL files from the existing default c: into the a: drive) Example: c>copy a:*.* b: (means copy ALL files from a: to b:) Example: a>del finance.* (delete files from the a: drive which begin with finance and have ANY file extension size or character type.) ██ COPY ██ (internal) copies one or several files to a disk or directory. Copy can duplicate a file onto another disk or into a subdirectory (more on subdirectories later). Copy is the most flexible and powerful of the DOS commands! Use the copy command with the wildcards seen above for even more flexibility. Example: b>copy zip.doc a: (copy zip.doc from b: drive to a: drive.) Example: a>copy c:why.me b: (copy why.com from c: drive to b: drive.) Example: c>copy c:fuss.txt b:whine.txt (copy fuss.txt from c: drive to b: drive and rename it whine.txt) Copy and /v verifies a good transfer or copy. Example: a>copy whine.bat b:/v Means copy the disk file whine.bat to the b: drive and then VERIFY this is a good copy. Verify is also an independent DOS command. Copy and the + symbol COMBINES two or more files into one larger file. Useful for combining two wordprocessor files into one larger file. Example: a> copy files.old+files.new files.all (The NEW file = files.all) Copy can send data to the printer. Example: b>copy files.new prn Example: b>copy files.new>prn. Copy CON (copy from the console or keyboard) can prepare batch files and autoexec.bat files to automate many DOS operations (examples below). In this fashion copy can create a new file and act like a very simple word processor! Example: a>copy con autoexec.bat (press enter) a>123 (press enter) a>^Z (press enter) In the last line ^Z is produced by either pressing F6 (function key 6) or holding down control key and z key together. This file means (first line) create a file named autoexec.bat as typed from the keyboard or con (console). (Second line) execute the program named 123. (Final line) end of my orders from the keyboard - prepare the file and stash it on the disk. ██ VERIFY ██ (internal) checks file copying operations to make sure a newly copied file is identical to its companion. It is usually added as a /V command at the end of a copy command, but also is a separate DOS command. Typing verify all by itself simply reports whether verify is currently on or off. Example: c>verify on (turns on verify function until you turn it off) Example b>verify off (turns off verify function until you turn it on) ██ DATE and TIME ██ (internal) A calendar and clock exist within DOS. On some computers it automatically is updated and kept current. On other computers (without a clock card or chip installed) you type in the date and time on startup. If you don't type in the date and time manually or have an automatic clock chip which does this, the default values will be 1/1/80 and 00:00:00.00 for date and time respectively. You can enter the date with hyphens (-) or slashes (/). Do not enter the day of the week (e.g., Monday) even though it may show on the monitor. The PC will calculate this for you automatically. A two digit year references dates between 1980 and 1999. In 2000 you must use four digits. The time setting references a 24 hour military time clock (e.g., 1300 hours = 1PM). Date and time data is important to DOS since it is attached to all files to keep track of when they were created so you can determine which file is most recent. Example: b>time Example: a>date ██ DEL or ERASE ██ (internal) deletes files or groups of files. Use DEL*.* to erase all files from a disk. See our previous mention of wildcards (* and ?). If you make a mistake, certain non-DOS utilities (e.g., Nortons Utilities and PC-Tools) can un- delete a deleted file. But DOS cannot do this! Be careful - a typographic mistake can delete an unintended file! Deleting old files is a necessary operation, though, which frees up space on a disk. Hard disk users may prefer to move files to a floppy to free up space yet still retain a backup copy of the file in case of need. Example: a>del whine.txt Example: b>del 784.wks Example: a>del *.wks (notice the use of the * wildcard we mentioned earlier!) Example: a>del old.* (notice the use of the * wildcard we mentioned earlier!) Example: c>del ??.rxd (notice the use of the ? wildcard we mentioned earlier!) ██ DISKCOPY ██ (external) copies entire contents of one floppy to another. Some DOS versions (Ver 2.11) require you to first format the blank disk while later versions (Ver 3.1 and higher) sense an unformatted disk and first format it then proceed with the diskcopy. Diskcopy is a wise idea since disks wear out after several hundred hours of operation. The /1 argument means copy to side 0 of the disk only. All information on the target disk will be destroyed and over-written with the new information, so be careful! Example: a>diskcopy a: b: (copy the contents of a: floppy to b: floppy) Example: a>diskcopy a: b:/1 (copy the partial contents of a: floppy to b: floppy using single side of disk only) ██ COMP and DISKCOMP ██ (external) compare two files or disks. Diskcomp is frequently used after diskcopy operations. These commands ensure identical accuracy of the copied files or disks. Example: a>comp a:fuzz.txt b:thatch.txt (compares two files) Example: a>diskcomp a: b: (compares two entire disks) ██ CLS ██ (internal) clears the screen and puts the cursor in the home (upper left) position. Useful. Try it! Example: a>cls ██ FORMAT ██ (external) Prepares a blank floppy to receive data. Think of a fresh disk as blank paper. DOS prefers graph paper with little boxes drawn on it to receive data. Each little box stores a computer word or "byte." Format erases any old files on a disk (be careful!) Format prepares the tracks and sectors which will receive the data. All disks must first be formatted prior to use. Example: b>format a: (format floppy in a: drive) Example: c>format a:/s (format floppy in a: AND add system files) Example: a>format (format the disk in the DEFAULT a: drive). Full command syntax is: format d:/s/1/8/b/v In the above example, d: tells where the disk is. /s put the system files IBMDOS.COM and IBMBIO.COM on the disk. /1 formats one side of the disk only. /8 formats as 8 sectors for use the older DOS 1.1. /b formats as 8 sectors per track and leaves room for the DOS system files. /v puts a volume label onto the disk for future identification. Tip: Only new (empty) formatted disks can receive the system files (IBMBIO.COM and IBMDOS.COM). Once you put a few files on the floppy, the system files will not fit since track 0, sector 0 have been used. Remember that the system files are designed to start the computer and MUST start on track 0, sector 0, However very few of your floppies NEED the system files: just the one or two which actually start the PC. Tip: Danger! a>format c: wipes out your hard drive! Also c> del *.* wipes out hard drive. ██ REN or RENAME ██ (internal) changes name of a file to another new name. Destroys old name. Usually you will use this when you want to change on old backup file to another name so that it can be used by a program again. Wildcards are allowed but can cause trouble - be careful. If the new file name already exists, the ren command will give you an error message as a safety measure. Example: a>ren old.txt new.txt Tip: Use the copy command instead of rename if you want to KEEP the old file and its old name, and want another copy of that file with a new name. See the THIRD example given in the copy command. ██ VER ██ Shows the DOS version number. Example: a>ver ██ VOL ██ Displays a volume label, if one exists on a particular hard or floppy disk. The label is a name you can give the disk when it is first formatted. It can contain names, dates or helpful reminders much like the title on the cover of a book. Some special utilities help you change the volume label AFTER formatting has taken place. Example: c>vol ██ SYS ██ (external) copies the hidden files (BIO and SYS) to another disk which has been already formatted. This command makes a disk floppy bootable to the computer - you no longer need DOS to start the machine. The newly made disk with the two hidden files will boot (start) the machine by itself. The basic purpose of the SYS and format/s commands are to make a disk self-starting or self booting. The command FORMAT/S first formats a floppy then adds the hidden files. Example: a>sys b: (used when the disk is already formatted) Example: a>format b:/s (does same thing but first formats blank disk) Example: a>format b:/s/v (verify also used) ██ CHKDSK ██ (external) checks contents of a disk for errors. Chkdsk/f fixes minor file allocation table (FAT) errors. Chkdsk/v (v means verbose) displays all filenames as it works. Followed by a filename, chkdsk checks only that file. Always use the version of chkdsk which came with your DOS disk. Switching to a different version from another disk can do damage! Below is a sample display produced by running chkdsk on a floppy disk. The first three lines of the report tell about the disk. The last two tell about the RAM memory inside the computer. c>chkdsk b: produces following 362496 bytes total disk space 251904 bytes in 26 user files 110592 bytes available on disk 655360 bytes total memory 234016 bytes free Example: a>chkdsk b: (check b: floppy, all files) Example: c>chkdsk c:\*.* (check for contiguity of files in root of c: drive) Example: a>chkdsk b:this.doc/f/v (check only the file this.doc on b:floppy. Give verbose report and attempt to fix any errors) ██ FDISK ██ (external) prepares hard drive for data. First use fdisk then use format c:/s/v for second step. Some hard disks come shipped with fdisk already run and only need final formatting. Running fdisk is also known as partitioning the hard disk. Example: a>fdisk ██ LABEL ██ (external) attaches volume label or header to a floppy. Like stamping a book with a title. Only in DOS 3.0 and above. Some utilities can add this feature to DOS 2.11 and below. Example: a>label b:expenses.com ██ CTRL & PRTSC ██ (internal) aren't really DOS commands but a combination of two keystrokes at the same time which sends all displayed data to the printer until you hit the same two keys to turn the command off. This allows you to print directory listings or files of interest. Remember to turn command off when finished. Press CTRL-PRTSC to toggle the printer on and print anything which goes to the monitor screen, then press CTRL-PRTSC to toggle the printer off when you have all you need printed. ██ SHIFT & PRTSC ██ (internal) two key combination which copies only the current screen to your printer. DOS also uses device (equipment) names within commands. For example you can talk to your printer on keyboard by using the proper DOS name. Each name is unique. ██ CON ██ Is the name for the keyboard and monitor. Below is a repeat of a previous example using the con device name. Copy CON ("copy from the console or keyboard) can prepare batch files and autoexec.bat files to automate many DOS operations (examples below). In this fashion copy can create a new file and act like a very simple word processor! Example: a>copy con autoexec.bat (press enter) a>123 (press enter) a>^Z (press enter) ██ AUX: or COM1 ██ Is the first ansynchronous communication port which usually has a modem, serial printer or mouse connected to it. COM2 is the second port. PC's can have up to 4 serial ports. ██ PRN or LPT1 ██ Is the first parallel port which is usually used with a printer. LPT2 is the second printer. By the way, a PORT is an electrial socket on the back of the PC where a cable of some type plugs in. ██ CAS1 ██ Is an antique term still available within DOS which refers to the early PC days when a cassette recorder was used for storing data rather than floppies. This is the cassette recorder port. ██ NUL ██ Is a test device. Anything sent to nul goes nowhere. However it is useful in testing DOS batch programs or simply sending excess garbage from a screen report to nul (nowhere) thus uncluttering a busy screen. Odd but useful in its own right! ████████████████████████████████████████████████████████████████ SUBDIRECTORIES - LITTLE BOXES IN THE DISK DRIVE ████████████████████████████████████████████████████████████████ Floppy disks have a relatively limited capacity to store files - limited in comparison to the seemingly expansive space on a hard drive. To find a necessary file name on a floppy, just use the DIR or directory command. However, on a hard disk things get a little out of hand with hundreds of files all listed on the same screen. In version 2.0 of DOS and above, a solution is obtained by adding subdirectories and pathnames to manage the location and organization of file storage. A path is nothing more than a "trail" or "direction post" which helps DOS find a particular file out of the hundreds which may be located on a hard drive. This pathname is facilitated by the use of multiple directories (called subdirectories) on a single disk. In this fashion you sort files into groups in a specific place on the drive. By the way, a subdirectory is itself a small file and does occupy space on the disk. You could compare a hard or floppy disk to a department store. The store might sell toys, books and clothes. Similar items go in the same department or area. A disk also has the capacity for many separate areas in which to place files. DOS refers to these with a main central directory (root directory) and subdirectories branching below it. You can create a subdirectory named TEXT which contains all your word processing documents. Computer utilities could be in a subdirectory called UTIL, and so on. In diagramatic form this might be seen in a simple example as: ROOT (CENTRAL) DIRECTORY (contains startup files) | | ---------------------------------------------------------- | | | | | | DATABASE SUBDIRECTORY SPREADSHEET SUBDIRECTORY GAMES SUBDIRECTORY | | | | | | | | data files business files PERSONAL games files | | ---------- | | | | Earnings files Tax files On the screen, a listing of any subdirectory might show the first two entries mysteriously named . and .. (single dot and double dot). The first dot is a name for the subdirectory itself. The double dot is a name for the parent (higher) directory one level up. Anytime that a subdirectory can be referred to, one can use . or .. For example, if you want to copy all of a diskette, you could use copy A:. (A: single dot) instead of copy A:*.* or A:\*.* Be careful to use short pathnames, especially in the DOS search PATH. A long path name (example: \this\that\another\yik\yak) slows down DOS searches and is a pain to type out. When DOS first starts or boots up, you always begin in the root directory. Notice that pathnames use the backslash (\) as their main "roadpost." The correct name of a file always includes its path. Thus while we might talk about a file named PCL.EXE its REAL NAME if it were in a subdirectory area of a hard disk might be \this\that\thing\place\PCL.EXE. Most hard drive users include a PATH command within their autoexec.bat file to allow DOS to find the location of all the files. In this way you DON'T have to change directories manually - unless you want to - for the file to execute. DOS will simply consult the PATH established when the computer started and read in the autoexec.bat to find all files regardless of subdirectory location. The DOS commands MD, RD, and CD allow you to make, remove, and change among subdirectories. They are of marginal use on a floppy but essential use on a hard drive which may have hundreds of (hard to locate) files. Frequently the main (root) directory is where startup files are stored. The mark of a good main or root directory is that a DIR listing of the root should fill only ONE screen and not scroll down with many screens extraneous files. ██ MD or MKDIR ██ (internal) makes a subdirectory and assigns it a name or Example: a>md\data Example: c>md c:\data\files ██ RD or RMDIR ██ (internal) removes an empty subdirectory (it cannot remove a subdirectory already loaded with files as a safety measure - use the DEL command to first clear a subdirectory.) The root (main) directory cannot be removed. Example: b>rd\letters\financial (removes financial subdirectory below letters subdirectory and root directory) ██ CD or CHDIR ██ (internal) changes the current (active) subdirectory or directory. CD\ brings you to the root (main directory) no matter where you are. Example: a>cd\ (change to the root or uppermost directory) Example: c>cd\data (change to subdirectory named data below the root) Example: b>cd\data\financial ████████████████████████████████████████████████████████████████ TURNING ON THE PC - THE ELEGANT BALLET OF DOS TECHNOLOGY ████████████████████████████████████████████████████████████████ The following description is an optional tutorial but may be interesting for those curious about the starting sequence when a computer is first turned on and what the role of DOS is in this rather "elegant electronic ballet." The command processor mentioned earlier (i.e., COMMAND.COM) is also a file which resides on the disk but once it is read into the RAM chip memory of the computer it stays or resides there until the machine is turned off. Sometimes you may even need to load a second copy of COMMAND.COM and at other times, some application programs and games provide their own command processor. Basically COMMAND.COM watches for keystrokes from your keyboard and tries to execute commands and actions based on what it finds. That is why it is called a COMMAND PROCESSOR. The input/output system consists of two system files (which live on the DOS disk) plus a ROM (read only memory) chip which also contains software instructions wired directly into the circuits of your computer. The two system files which are on the DOS disk are normally hidden and not available for changing. The most elemental and necessary part of the input/output system is called the BIOS or basic input/output system. The BIOS consists of the ROM chip on the computer's main circuit board we mentioned earlier plus one of the hidden files on the DOS disk called IBMBIO.COM (or IO.SYS). The other hidden file on the DOS disk, IBMDOS.COM (or MSDOS.SYS), is the main file handling system for the computer. IBMDOS.COM hides inside it a portion of software for disk based files and a portion for non-disk peripherals. The two files (IBMDOS.COM and IBMBIO.COM) are necessary because non-disk peripherals require data as strings of characters (one after another in a long line) while disks move their files about in large data groups known as blocks. Let's jump back to COMMAND.COM which provides three services for the computer: it handles critical errors and problems. If your printer is not turned on at the right time or a disk drive door is open, COMMAND.COM finds out and attempts to report a message or suggest a remedy. It also handles critical interrupts which is a technical way of saying it takes care of demands and priorities imposed by the differing parts of the hardware. If you hit the Ctrl-Break key combination to stop a DOS operation, this is a critical interrupt which COMMAND.COM must deal with. Finally it performs end of program services which are routine chores like making more RAM memory available when a program finishes its job or reloading parts of itself when needed. In addition it also places the familiar prompt C> or A> on the screen and listens for commands you might type. Essentially, COMMAND.COM instructs the rest of the DOS series of programs what to do. When you first turn on the switch to start the computer in the morning, the machine goes through a process called "booting." This derives from the arcane but descriptive process which refers to how the machine literally picks itself up by the "bootstraps." In the first stage of "booting up," the machine begins by testing its memory RAM chips and other components in a power on self test (POST). After this, the left or top A: floppy drive spins and if no disk is available the hard drive light flickers as the machine searches for further clues about starting itself. Initially the ROM chip BIOS wired inside the machine loads track 0, sector 0 of the disk. This disk sector contains a very small program (boot loader) which reads the rest of the input/output system stored on the disk. Next the boot loader reads the input/output system (IBMBIO.COM and IBMDOS.COM) into the system. IBMBIO.COM initializes the hardware of the machine and runs a small file named CONFIG.SYS (if available) and finally moves IBMDOS.COM into its normal location in RAM memory. Finally, IBMDOS.COM loads COMMAND.COM and turns control over to it. COMMAND.COM runs the AUTOEXEC.BAT startup file (if found) and finally control is given to the keyboard and you. It is a long process with each step depending on the previous! An elegant ballet, fascinatingly complex, but necessary for the PC to function. Why not wire this permanently into the machine on a ROM (read only memory) chip? Some machines do, but the main advantage of having this information stored on a disk is that it can be updated and revised easily via a change of a floppy disk. The machine can revise its operating system quickly by simply using a different or later version of DOS (or even an operating system other than DOS such as UNIX or other operating systems.) This is what gives the PC such flexibility to change and upgrade to a newer operating system without the expense of tearing down or even replacing the machine. You simply change the floppy disk and you have a new way of doing business! Simplicity, elegance and ease of changing software is what this means for the computer user.