The controller of floppi - disk
(FDCH 765 or 8272A) RS AT usually supports only eight possible lengths
of the zone of data of sector, namely:  0 (128) byte, 1 (256 bytes), 2
(512 bytes), 3 (1024 bytes), 4 (2048 bytes), 5 (4096 bytes), 6 (8192
bytes) and 7 (16384 bytes).  The overall length of sector, together
with the heading and the bytes CHRCH, although has the dimension of
angle, it is measured in the bytes, namely:  length 0 corresponds to
190 bytes, 1 - 318, 2 - 574, 3 - 1086, 4 - 2110, 5 - 4150, 6 - 8254, 7
- 16446.

The gaps/intervals between the adjacent sectors from the end of
previous to the beginning following can take values from 1 to 255
(besides gap/interval from the last sector on the path/track to the
first, which it can be any).  DOS uses only length of sectors 2,
however, on the paths/tracks can meet the sectors with another length
precisely for the purpose of protection diskettes.  Each sector has a
heading (ID), which consists of four bytes (Ch, yu, r, n).  Ch - the
number of cylinder, Yu - the number of head, R - number of sector
(counting from 1, in all remaining cases from 0), N - length of sector
(0... 7).  Have in the form that the heading ID is intended only for
the identification of sector by controller, and completely it does not
give representation about the true position of sector on the diskette
and its parameters, i.e.  sector with ID 7,0,124,4 can be
arranged/located where conveniently, but not only on path/track 7,0.
Moreover, Ch, yu, r, n can have any, including physically senseless
values from 0 to 255.  The true parameters of sector can completely
not coincide with those indicated in the heading, which is used for
purposes of protection.  In this case occur some limitations, for
example, sector the indicated in the identifier length of more than 7
cannot be correctly considered controller.  Density writing - this is
the parameter, which characterizes a maximally possible number of bits
of the written down information on one path/track.  It depends on the
velocity of priyema/vydachi of information by controller and the
rotational speed diskettes.  Controller by hardware supports three
velocities:  250, 300, 500 kbit/s.  The rotational speed diskette in
disk drives 5.25 " is 5 r/s for the disk drives to 360K and 6 r/s for
the disk drives in Y.2M. the speed of rotation 3.5 " the diskette of
always 5 r/s.  Density writing is proportional to the ratio of the
velocity of the output of information by controller to the angular
rate of rotation diskettes.  Thus, are possible 5 different values of
density writing (value of 250/5 and 300/6 they coincide).  In the
window of preparation for DOS to format and Report file by them
correspond to the recording/record Of losh (250/6), To double (250/5
or 300/6), medium (300/5), To yuigyu (500/6) and Tsuad (500/5).  It is
necessary to note that density writing Losh and Medium are not
supported BIOS, but they can be used for the purpose of protection.