CD - ROM
(Compact Disc - Read Only Memory)
(Compact Disc - Read Only Memory)
· It is a pre-pressed optical compact disc which contains data. The name is an acronym which stands for "Compact Disc Read-Only Memory". Computers can read CD-ROMs, but cannot write to CD-ROMs which are not writable or erasable.
· CD-ROMs are identical in appearance to audio CDs, and data are stored and retrieved in a very similar manner (only differing from audio CDs in the standards used to store the data). Discs are made from a 1.2 mm thick disc of polycarbonate plastic, with a thin layer of aluminium to make a reflective surface. The most common size of CD-ROM is 120 mm in diameter, though the smaller Mini CD standard with an 80 mm diameter, as well as numerous non-standard sizes and shapes (e.g., business card-sized media) are also available. |
Advantages
· The formats are well standardized and the technology is stable; this ensures a high degree of compatibility.
· The cost of information storage per information unit is low. · The disks are easy to store, to transport and to mail. · Random access to information is possible. · CD-ROM systems are easy to use. |
Disadvantages
· Data error is frequent
· Can be broken if dropped · Fairly fragile, easy to snap or scratch · Smaller storage capacity than a hard drive or DVD · Slower to access than the hard disk. |
Using CD - ROM in Education
· Most of the current CD-ROM products on the market are database applications in which very large volumes of text and numerical data is available for searching. Examples in this category include dictionaries, encyclopedias, chemical information, statistical records and census data. Results of a search are often enhanced by the display of graphs and photographs.
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