Computers today. Гурьянова В.И. - 28 стр.

provides a software platform on top of which other programs can run. Every computer
must have an OS to function, even if it is simply the boot files from DOS or Windows.
      Different operating systems will use different file systems to access the
storage media and keep track of the locations in which data has been stored; the
file system is the way the OS organizes and accesses the files on a disk. Being a
collection of information, a file on your disk can be compared to a file folder in
a desk drawer. For example, file folders might contain business letters from cli-
ents and important memos from associates. File on your disk could also contain
business letters and memos. All programs, texts and data on your disk reside in
files and each file has a unique name. You refer to files by their filenames. You
create a file each time you enter and save data or text at your terminal. Files are
also created when you write programs and save them on your disks. The names
of files are kept in directories on a disk. These directories also contain informa-
tion about the size of the files and the dates they were created and updated. The
directory you are working in is called your working directory.
      The name of a typical MS-DOS file looks like this: newfile.doc. The name of
the file consists of two parts. The filename is newfile and the filename extension is
.doc. A filename can be from 1 to 8 characters long. The filename extension is op-
tional, and can be three or fewer characters. You can type any filename in small or
capital letters. Directory information (name, size, date and time) about the file new-
file.doc is displayed on your screen. If drive A is the default drive, MS-DOS auto-
matically searches the disk in drive A for the filename new file; so it is not necessary
to type the drive name. A drive name is needed if you want to tell MS-DOS to look
through a different drive to find a file. Your filenames will probably be made up of
letters and numbers, but other characters are also allowed. Valid characters for file-
name extensions are the same as those for filenames.
      MS-DOS treats some devices names specially, and certain three-letter names
are reserved for the names of these devices. These three-letter names cannot be used
as filenames, but they can be used as extensions. MS-DOS is powerful and useful
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