CD-ROM Technology

# 2 CD-ROM Technology

Contents of this section

    "CD-ROM is read-only memory, and audio compact disc system is
    available as package-media of digital data for those purpose. For
    playing audio CD, please insert Head-phone jack."
    --- from a CD-ROM instruction manual

Don't Panic! The world of CD-ROM technology is not as confusing as your instruction manual.

CD-ROM stands for Compact Disc Read-Only Memory, a mass storage medium utilizing an optical laser to read microscopic pits on the aluminized layer of a polycarbonate disc. The same format is used for audio Compact Discs. Because of its high storage capacity, reliability, and low cost, CD-ROM has become an increasingly popular storage media.

The storage capacity of a CD-ROM disc is approximately 650 megabytes, equivalent to over 500 high density 3.5" floppy disks or roughly 250,000 typed pages.

First generation drives (known as single speed), provide a transfer rate of approximately 150 kilobytes per second. Double speed drives are commonly available, and triple and quad speed drives have recently been introduced.

Most CD-ROM drives use either the Small Computer Systems Interface (SCSI) or a vendor proprietary interface. They also typically support playing audio CDs via an external headphone jack or line level output.

CD-ROMs are usually formatted with an ISO-9660 (formerly called High Sierra) file system. This format restricts filenames to the MS-DOS style (8+3 characters). The Rock Ridge Extensions use undefined fields in the ISO-9660 standard to support longer filenames and additional Unix style information (e.g. file ownership, symbolic links, etc.).

PhotoCD is a standard developed by Kodak for storing photographic images as digital data on a CD-ROM. With appropriate software, you can view the images on a computer, manipulate them, or send them to a printer.

CD recorders (CD-R) have recently become available. They use a different media and specialized equipment for recording, but the resulting disc can be read by any CD-ROM drive.

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