Working of compact disk - computer architecture, Computer Engineering

Assignment Help:

Working of compact disk:

A CD is built from 1.2 mm thick, approximately all-pure polycarbonate plastic and its weighs is approximately 15-20 grams. From the core outward components are at the center (spindle) hole, the clamping area (stacking ring), the first-shift area (clamping ring), the information (data) area the second-transition area (mirror band), , and the rim.

A thin layer of aluminum or, rarely, gold is applied to the surface to make it reflective, and is protected by a film of lacquer that is usually spin coated directly on top of the reflective layer, on which the label print is applied. General printing methods for CDs are and offset printing and screen-printing

CD data are stored as a series of tiny indentations called -pits? which is encoded in a spiral track molded into the top of the polycarbonate layer. The areas among pits are called -lands?.  Each pit is about 100 nm deep by 500 nm wide, and varies from 850 nm to 3.5 µm in the length.

The distance among the tracks, the pitch is 1.6 µm. CD is read by focusing a 780 nm wavelength (near infrared) semiconductor laser throughout the bottom of the polycarbonate layer. The modification in height among pits (in fact ridges as seen by the laser) and lands results in a difference in intensity in the light reflected. By measuring the intensity change having photodiode, the data may be read from the disc.

The lands and pits both do not directly represent the 0 and 1 of binary data. Instead of it, Non-return- to-zero, inverted (NRZI) encoding is used for this purpose: a change from pit to land or land to pit denote a 1, whereas no change denote a series of 0. There have to be at least 2 and no more than 10 zeros between each one that is defined by the length of the pit. This is decoded in turn by reversing the Eight -to-Fourteen Modulation which is used in mastering the disc, and afterwards reversing the Cross-Interleaved Reed-Solomon Coding, at last revealing the raw data stored on the disc.

CDs are susceptible to damage from both every day use and environmental contact. Pits are much nearer to the label side of a disc, so that dirt and defects on the clear side can be out of focus at the playback time. Thus, CDs suffer from scratch and damage on the label side while scratches on the clear side may be repaired by refilling them with same refractive plastic, or by polishing carefully. First music CDs were known to suffer from or "laser rot", or "CD rot", in which the internal reflective layer degrades. When this take place the CD may become unplayable.


Related Discussions:- Working of compact disk - computer architecture

Typewriters information distribution, TYPEWRITERS : Typewriter is the most...

TYPEWRITERS : Typewriter is the most common machine used in almost all offices. Typewritten letters are attractive in appearance as compared to handwritten ones. The same matter c

C++ program on pebble merchant, how to solve pebble merchant problem.? codi...

how to solve pebble merchant problem.? coding for it..!

Scanning tips, Don't scan at more resolution than needed. This saves both D...

Don't scan at more resolution than needed. This saves both Disk and time Space. Typically itisn't useful to scan at more than optical resolution because it adds no new informa

Enumerate the history of computers, Enumerate the History of computers ...

Enumerate the History of computers Basic information about technological development trends in computer in past and its projections in future. If you want to know about compute

What about division and multiply operations, Q. What about division and mul...

Q. What about division and multiply operations? In most of the older computers divisions and multiply were implemented using subtract/add and shift micro-operations. If a digit

Show packing and unpacking data, Q. Show Packing and Unpacking Data? P...

Q. Show Packing and Unpacking Data? Packing and Unpacking Data  pvm_packs - Pack active message buffer with arrays of prescribed data type: int info = pvm_pac

Define b2b - business to business, B2B - Business to Business  It is a...

B2B - Business to Business  It is a mode of conducting business among two or more companies over the Internet, rather than more traditional modes like as telephone, mail, and f

Displaying the towers of hanoi solution, Once you have a solution to the To...

Once you have a solution to the Towers of Hanoi problem, we want to improve the display of the solution. The details of the implementation are up to you. At a minimum, your impleme

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd