Everything You Want to Know about CD-ROM Is Here

What Is CD-ROM: Definition, Appearance and Read Principle

The contents of the article are all about CD-ROM, in this part, you will get to know what is CD-ROM based on three aspects. Let’s get to know it!

Definition of CD-ROM

CD-ROM Stands for Compact Disc Read-Only Memory. A CD-ROM is a type of computer memory in the form of a compact disc which contains data. This type of disc can only write data once, then the data on the disc is read-only which cannot be altered or erased, and the information will be permanently stored on the disc. Information stored on the disc will be read by the disc drive during use.

This kind of CD format was originally designed for the storage and playback of music. In 1985, the Yellow Book standard developed by SONY and Philips made this format adaptable to a variety of binary data. Some CD-ROMs store both music and computer data, then the music can be played by a CD player, while computer data can be processed by a computer.

Appearance of CD-ROM

CD-ROM is the same in appearance as audio CD. Meanwhile, they store and retrieve data in a very similar way (unlike audio CD in the standard for storing data only). The disc is made of 1.2 mm thick polycarbonate plastic disc with a thin aluminum layer and can be made into a reflective surface.

The most common CD-ROM size is 120 mm in diameter, but smaller MINI CD is 80 mm in diameter, as well as various non-standard sizes and molded compact discs.

Read Principle of CD-ROM

Data is stored on the disc as a series of micro-indentations. Lasers are illuminated on the reflective surface of the disk to read patterns of pits and platforms lands (“pits”, the gaps between them referred to as “lands”).

Because the depth of the pits is about one-quarter to one-sixth of the laser wavelength used to read the CD, the phase of the reflected beam shifts relative to the incident beam, which causes destructive interference and reduces the intensity of the reflected beam. This will be converted to binary data.

It should be noted that if the surface of CD-ROM becomes dirty and scratched, it will reduce its readability. Although the disc is read from below, try to avoid using hard pens such as ballpoint pens to write on the front of the disc. It is easy to scratch the data layer under the protective layer.

Features of CD-ROM: Capacity, Usages, Advantages and Disadvantages.

Now you have a basic understanding of what is CD-ROM, the following part will list some of its features to you.

Capacity of CD-ROM

The invention of paper greatly promoted the progress of human civilization. It recorded the development history of human civilization and created a number of new industries. From the point of view of information storage, CD-ROM can be regarded as a new type of paper.

A small plastic disc with a diameter of less than 120 mm and a weight of less than 20 grams has a storage capacity of more than 600 megabytes. If you simply store text, a CD-ROM is equivalent to 150,000 16-page sheets of paper, enough to hold hundreds of large books.

Usages of CD-ROM

You already know it can contain data, what about the actual usages? You can use it as a backup disc since it can only be read while cannot be rewritten.

The CD-ROM can store audio and data. Audio CDs can be played by any CD player, such as most newer car stereo systems or portable CD players.

The CD-ROM drive can open documents on the data CD, such as music files, pictures, word documents and other files. However, CD-ROM drives cannot write information to the CD (burn) because they are read-only drives. Mostly, data CDs are read by a CD-ROM drive on a computer.

Advantages and Disadvantages of CD-ROM

What are the advantages and disadvantages of CD-ROM? For the advantages: it is easy to use, easy to move, cheap, and has a long life. For the disadvantages: It is easy to be damaged, non-modifiable, and keep limited data.