Acronis TrueImage Deluxe
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There can be up to several tens of thousands of cylinders per disk. The
higher the write density on the disk, the more cylinders can be created on it
and the larger the capacity of the disk.
This design has many technical implementation peculiarities, but we will not
discussing those here.
A.2
Operating System and Hard Disks
You know that hard disks are used to store information. You also know (see
A.1 «Hard Disk Organization») that information is stored in sectors, and the
sectors appear on disks by way of low-level formatting. Each sector contains
the smallest possible 512-byte data block.
Data blocks of larger size are stored in chains of such sectors. Each sector of
a chain contains the address of the next sector in the chain or the marker
telling that this sector is the last one in its service area. Chains of sectors
make a
file
. The address (number) of the first sector of a file is stored in the
file allocation table (FAT).
All applications you are familiar with – office applications (text and graphical
editors, spreadsheet processors) – and documents, tables, images, e-mail clients
and Internet access software, and games – are stored on hard disks as files.
Files are grouped into folders to make working with them more convenient.
Among various software the most important one is the operating system.
An operating system provides all other applications running under its control
with basic input/output access to all the resources of the PC, be that the
CPU, memory, or external devices (monitor, hard disks, floppy disks,
CD-ROM, DVD, printer). All applications are loaded into memory from a hard
disk and are executed under the control of the operating system.
It would have been very inconvenient for a user to use data on disks if
he/she had to deal only with addresses (numbers) of sectors comprising a
file. That is why every file in the file system has its
name
. In DOS and
Windows 3.x operating systems the name of the file contained 8 characters
followed by a dot (.), which, in its turn, was followed by three more
characters of the extension (or the type of the file). There could be fewer
characters in the name and/or extension, and there were limitations as to
what characters could be included in names and extensions.
Windows NT and newer OS versions allow files names that are up to 255
characters long. Full file name (including the disk letter and the name of the
folder containing the file) can be up to 260 characters long, however it is not
recommended using file names longer than 50-70 characters.
Other operating systems, like Linux, have never had such strict limitations on
file names as did DOS or Windows. The name of the file in Linux can be up
