Reading and Recording Bits on Hard.

Reading and Recording Bits on Hard.

Coil core disk magnetic film.

Before any data can be written to disk, iron particles scattered randomly on a magnetic film
(Magnetic film) overlying the surface of the disk (disk), which is similar to the surface of the magnetic tapes of audio and video.
To organize such data particles, the electrical pulses pass through a coil (coil) wire surrounding the core
(Core) of iron in the head mechanism of the read / write drive. The head is suspended over the disc surface.
The electricity turns in the core an electromagnet capable of moving molecules of the casing, as a child
uses a magnet to attract iron filings.

The coil induces a magnetic field in the core so that it passes through the disk. The field, in turn, magnetizes the molecules
iron of the disc surface, forcing them to align them with their positive poles facing the negative pole
head read / write, and their negative poles facing the positive pole of the head. The positive and negative poles
in the drawing are represented by the colors red and blue, respectively.

After that head creates a magnetic strip on the disk in motion a second track is created beside her. Together, the
two bands represent the smallest element that a computer is able to create - one bit. If the bit representing the first binary
after creating the first track, the current in the coil reverses so that the magnetic poles of the core are exchanged and
molecules of the second band are aligned in the opposite direction. If the bit represents a binary 0, the molecules of both
bands are aligned in the same direction.

When the second bit is stored, the polarity of a first track is always opposite to that of the previous track to indicate that
is a new bit. Even the drive slower only takes a split second to create each range. Bits
Stored in the illustration below represent the binary number 1011, equivalent to 11 in decimal numbers.

Fourth bit (1) Third bit (1) Second bit (0) First bit (1)
To read the data, no electric current is sent to the read / write when it passes through the disk. The
What takes place is a process inverse to that of magnetic recording. The banks of polarized molecules on the surface of the disk
transformed into tiny magnets which create a magnetic field which passes through the head read / write. The movement
head in the magnetic field generates an electric current that moves in either direction through the coil wires.
The current flow depends on the polarity of the tracks. To capture the movement of the chain, the computer can tell whether the
head read / write is going on about 1 or 0.

Source: Evolution of Computers