Computers as a Second LanguageComputers as a Second LanguageComputer Fundamentals
| YOU HAVE MENTIONED THE OPERATING SYSTEM (OS) NUMEROUS
TIMES, BUT WHAT IS DOS?  As
mentioned at the beginning of the previous section, only a
PART of the Operating System of a computer is contained in the
ROM chip. The greater majority comes from your hard drive and is loaded into
RAM every time you turn the computer on. This portion of the Operating System
is called DOS, meaning Disk-based
Operating System. A company called Microsoft
Corporation wrote the Disk-based Operating System which is used on most IBM and
IBM-compatible computers today.There is a major
advantage of an Operating System which is mostly Disk-based rather than
ROM-based. When the manufacturer changes or updates the Operating System, they
simply provide new disks containing the new system. The new programs are then
simply installed onto your hard drive. With a ROM-based system (such as the
AMIGA), when a new version comes out, you have to
bring your computer to a service depot to remove the old ROM chip and install
an entirely new one.The newer Disk-based Operating
System from Microsoft Corporation are Windows 2000,
Windows ME (Millennium Edition) and Windows
98SE. For convenience, Microsoft now provides these Operating Systems
on compact discs (CD) instead of having to ship dozens of
floppy disks. This makes it much faster and easier to copy all the Operating
System programs to your hard drive. Of course, when you buy a computer, the
dealer has already set everything up for you.As
your computer goes through its startup process, the Windows Operating System is
loaded from the hard drive into the computer's RAM, and it entirely changes the
way an IBM or IBM-compatible computer performs. In fact, they start to look
very similar to a Macintosh or AMIGA computer. IBM
users have long envied the easier-to-use Macintosh environment with its
mouse-driven pictorial interface. Now they can have it with any of Microsoft's
Windows Operating Systems.The Disk-based
portion of the Operating System also contains many more instructions that the
computer requires only on an occasional basis. Whereas the ROM-based Operating
System instructions contain "essential services" to assure that the computer
functions properly at all times, there are other "non-essential" operations the
computer can perform which do not have to be present in ROM. For example,
suppose you have used a certain floppy disk for several weeks and it is getting
filled with a lot of your important work. It is a very good idea to make a
duplicate copy of this disk. If you damaged or lost your original disk, it
could take weeks to reconstruct all your efforts! The computer program required
to make a duplicate copy of a disk is not within the Operating System ROM
because the OS is not dependent upon this program to keep the computer running.
Instead, the duplicating program is provided on the Windows CD
which comes with your computer when you purchase it. The program is called
DISKCOPY and it is installed on your hard disk drive. Again,
DOS means Disk-based
Operating System. The program you require is
disk-based (located on your hard disk) rather than ROM-based (located in
ROM).To copy a disk (using Windows),
you simply place the mouse pointer on the Floppy Disk icon and
select Copy Disk. This "tells" Windows to load the DISKCOPY
software from the hard disk into the computer's RAM. After the copying process
is completed, the DISKCOPY program is no longer required in RAM and the
computer can be used for another application.You
may be wondering why the manufacturer did not include the DISKCOPY program in
the computer's ROM even though you do not use it all the time. There are two
main reasons the DISKCOPY program is not in ROM. First, it is not an essential
program to keep the Operating System running. You will see later that there are
dozens of non-essential programs which could increase the size of the Operating
System ROM by 50-fold if every one was included in the ROM.
Second, by leaving non-essential programs on your hard disk, it is much easier
to update your computer as Operating System programs are revised and improved.
Whenever a new or improved version of the Operating System becomes available,
you simply need to acquire the latest version and copy the new files to your
hard drive. If everything was in ROM, you would literally have to take your
computer to the service department to have the ROM replaced whenever there was
an update. This would be costly for you and unbearably costly for the
manufacturer.Just as there are different
Operating System ROMs, there are different Disk-based Operating Systems. IBM
has PC-DOS for their older computers. For IBM-compatibles,
there is MS-DOS 6.21, Windows 95/98
Windows ME and Windows 2000 which were
written by Microsoft Corporation. The AMIGA has
AMIGA-DOS 3.0 and the Macintosh has System
9 and System 10. |
