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  Computer Dictionary : CD
 

Welcome to the eComputer Bay's Computer Dictionary - the free online dictionary of computer and technology terms. The goal of the Computer Dictionary is to not just define computer terms, but explain them as well.

Definitions of computer terms are helpful, but explanations with examples are even better. eComputer Bay contains hundreds of computer and technology terms, all with detailed explanations.

Use the Search Bar Below To Get Computer Definations And To Check out All the Terms Simply leave the Computer Term Blank...-



Computer Term

1. CD

Stands for "Compact Disc." CDs are circular discs that are 4.75 in (12 cm) in diameter. The CD standard was proposed by Sony and Philips in 1980 and the technology was introduced to the U.S. market in 1983. CDs can hold up to 700 MB of data or 80 minutes of audio. The data on a CD is stored as small notches on the disc and is read by a laser from an optical drive. The drives translate the notches (which represent 1's and 0's) into usable data.

The first CDs were audio CDs, which eventually replaced audio tapes (which earlier replaced records). Audio CDs have the advantage of allowing the user to jump to different places on the disc. CDs can also be listened to an unlimited number of times without losing quality. Audio tapes can start to lose quality after listening to them as few as ten times. This is because the laser that reads the data on a CD doesn't put pressure on the disc, whereas the playheads on a tape deck slowly wear away the magnetic strip on the tape.

In 1985, CD-ROMs hit the computer market. Because they could store far more information than floppy discs (700 MB compared to 1.4 MB), CDs soon became the most common software format. In 1988, the CD-R (CD-Recordable) technology was introduced, allowing computer users to burn their own CDs. However, this technology did not become mainstream until the late 1990s. A smaller 3" CD, called "CD-3" is also available and is readable by most tray-loading CD-ROM drives.

2. CD-R

Stands for "Compact Disc Recordable." CD-R discs are blank CDs that can record data written by a CD burner. The word "recordable" is used because CD-Rs are often used to record audio, which can be played back by most CD players. However, many other kinds of data can also be written to a CD-R, so the discs are also referred to as "writable CDs."

The data burned onto a CD-R disc is permanent, meaning it can not be altered or erased like the data on a hard drive. Typically, once a CD has been burned, it will not be able to record any more data. Some CD burning programs can record data as "sessions," allowing a disc to be written to mulitple times until it is full. Each session creates a new partition on the disc, meaning a computer will read a disc with multiple sessions as multiple discs. CD-RWs, on the other hand, can be erased and completely re-recorded. Like CDs, the data on CD-RWs cannot be altered, meaning the disc has to be completely erased each time you want to add new data.

3. CD-ROM

Stands for "Compact Disc Read-Only Memory." A CD-ROM is a CD that can be read by a computer with an optical drive. The "ROM" part of the term means the data on the disc is "read-only," or cannot altered or erased. Because of this feature and their large capacity, CD-ROMs are a great media format for retail software. The first CD-ROMs could hold about 600 MB of data, but now they can hold up to 700 MB. CD-ROMs share the same technology as audio CDs, but they are formatted differently, allowing them to store many types of data.

4. CD-RW

Stands for "Compact Disc Re-Writable." A CD-RW is a blank CD that can be written to by a CD burner. Unlike a CD-R (CD-Recordable), a CD-RW can be written to multiple times. The data burned on a CD-RW cannot be changed, but it can be erased. Therefore, you have to completely erase a CD-RW every time you want to change the files or add new data. While it may be somewhat inconvenient, this capability makes CD-RWs a good choice for making frequent backups. However, because CD-RWs can be erased, they don't store data reliably for as long as CD-Rs do. Therefore, you should use regular CD-Rs for long-term backups.

5. CDMA

Stands for "Code Division Multiple Access." CDMA is a wireless transmission technology that was developed during World War II by the English allies to avoid having their transmissions jammed. After the war ended, Qualcomm patented the technology and made it commercially available as a digital cellular technology. Now CDMA is a popular communications method used by many cell phone companies.

Unlike the GSM and TDMA technologies, CDMA transmits over the entire frequency range available. It does not assign a specific frequency to each user on the communications network. This method, called multiplexing, is what made the transmissions difficult to jam during World War II. Because CDMA does not limit each user's frequency range, there is more bandwidth available. This allows more users to communicate on the same network at one time than if each user was allotted a specific frequency range.

Because CDMA is a digital technology, analog audio signals must be digitized before being transmitted on the network. CDMA is used by 2G and 3G wireless communications and typically operates in the frequency range of 800 MHz to 1.9 GHz.



 
 



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