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BOOT CAMP 113
INTRODUCING DOS, PART 1
If you purchased your Windows PC within the last five years
and have no particular interest in games or specialist applications the chances
are that you have had little or nothing to do with DOS, apart from that brief
flash of text when you switch on your PC, and the occasional (or possibly not
so occasional) mysterious error messages. DOS, or to give it its full name is
the Microsoft Disc Operating System (MS-DOS) and it is the foundation upon
which Windows -- and Bill Gate’s enormous wealth -- have been built.
That’s really all you need to know, these days DOS exists
mainly in the background on a Windows 95/98 PC. Its importance has gradually
diminished with each subsequent release, nevertheless, it is well worth getting
acquainted with DOS since it can provide a lifeline to revive your PC and recover
data after a nasty crash or when Windows refuses to load. An understanding of
DOS will also help you weave your way through some of the more puzzling aspects
of Windows, so this week it’s back to basics for a brief but essential tutorial
on how your PC works and the way it manages files. Next week we’ll delve a
little deeper into the workings of DOS and run through some of the interesting things
it can do for you.
When you switch on your PC from cold it ‘boots’ up – from
the expression picking yourself up by your own bootstraps – and this starts a sequence
of events. Stage one is a brief diagnostic routine called Power On Self Test or
POST, when the computer checks its RAM chips, disc drives and other vital components,
if all’s well it bleeps once and goes on to stage two (more than one bleep
usually indicates a problem). The on-screen message appears ‘Starting Windows
98’ (or 95 etc.) and the first ‘Splash Screen’ with the Windows logo is
displayed and then disappears; the machine now starts to load and process a
number of DOS text files from the ‘root directory’ (more about that in a
moment) on the hard disc, the most important ones being ‘msdos.sys’, ‘io.sys’, ‘autoexec.bat’
and ‘config.sys’. Between them they tell the PC about the devices and
peripherals connected to the machine, and the software it is using. Then it’s
on to stage three, DOS is shunted to the sidelines as Windows loads and takes
command of the PC.
Windows now becomes the PCs primary operating system; it
controls how the computer’s hardware and software communicates and interacts and
presents you with the Graphical User Interface (GUI or ‘gooey). This is the familiar
Windows ‘desktop’, a simple to use pictorial analogy that allows you to use and
control your PC by moving a mouse pointer and clicking on icons or menu items. Essentially
DOS does the same job but without all the frills and pretty graphics; instead
of clicking on icons things are made to happen by typing in text commands and
keyboard actions. DOS interprets the commands and turns them into a language
the computer understands, called machine code.
Because DOS uses text-based instructions and doesn’t need layers
of extra software for colourful graphics it is much simpler than Windows. It is
also a lot faster, which is why until recently most of the best computer games
were DOS-based, though with the advent of faster processors, larger disc drives,
increased memory capacity and more advanced graphics controllers many recent
games work within Windows.
There are two ways to get into DOS. You can stop Windows from
loading during the boot up sequence (we’ll look at that method next week), or
you can start a DOS ‘session’ within Windows that allows you to peek inside DOS.
Click on the MS-DOS Prompt icon in Start > Programs. This loads a program
called Command.com, a black window opens on the screen and you will see a
Microsoft copyright message and below that a line that reads: C:\Windows>,
followed by a flashing cursor. This line is known as the Command Prompt and it
tells you a number of things. C: is the identification letter assigned to your
PC’s main hard disc drive, backslash Windows (\Windows) shows the directory
your PC is currently using, and the greater than symbol and cursor (>_)
indicates DOS is ready and waiting for an instruction or command. Now type in
the command ‘dir’ (without the quotation marks), a long list of file names will
flash past on the screen and the command prompt appears at the bottom of the
screen once again. The command ‘dir’ is short for Directory, it instructs the
computer to show the contents of the Windows directory.
At this stage it’s wise to look but not touch, DOS is
extremely powerful, a few careless keystrokes can wreak havoc, so close the window
in the usual way, by clicking on the ‘X’ icon in the top right hand corner. I f
you’re feeling bold, type the command ‘exit’ (without the quotation marks) and
the window disappears.
This brief encounter with DOS illustrates how information is
organised on your PC’s hard disc. The disc drive is like a filing cabinet
containing thousands of files – the basic storage unit for data and programs.
Related files are collected together into folders, directories and sub
directories (folders within folders). There is one exception to this rule and
that is the ‘root directory’ mentioned earlier. This is a special section of
the hard disc (represented by the blackslash after the C prompt (i.e. C:\). The
root directory is set aside for important systems files and directories that
the PC accesses when it first boots up, and this is where the DOS files live. In
other words – and this is the key point -- you can load DOS, and from there gain
access to any other directory on the hard disc, without Windows, that’s what
makes it so useful!
Next week – Introducing DOS, part 2
JARGON FILTER
MACHINE CODE
The basic language of computers, usually a form of binary
code, where instructions are represented by groups of ‘ones’ and ‘zeros’
RAM
Random Access Memory, a computer’s working memory, where
programs store data and information when they are running
SPLASH SCREEN
A usually pointless image or logo that appears on a PC screen
whilst a program is loading
TOP TIP
A few weeks ago in F!F!F!, we reminded you how to create a
new desktop icon that instantly opens a blank message window in Outlook
Express. This tip takes it one stage further, creating a personalised message
window for anyone that you frequently send emails to, with their address
automatically inserted. The basic procedure is the same as before; right-click into
an empty part of the desktop, select New and then Shortcut from the menu. In
the window that appears, in the Command Line field, type mailto:friendsname@freebienet.com,
where the part after mailto: is the recipient’s email address. Click Next, give
your new Shortcut a name then click Finish.
NEXT
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