CD-ROM (Compact Disk Read Only Memory) is most effective distribution medium for multimedia presentations. CD-ROM is a polycarbonate plastic base disc. It is 12-cm in diameter and can be used as storage purpose like floppy discs. CD-ROM opened a new era for storage technology switching from magnetic storage to optical technology. It has many advantages compared with floppy disks, such as vast storage capacity, compactness, reliability, durability and cheapness.

CD-ROM is ideal for the distribution of computer software, databases, courseware, maps, reference material and also for multimedia and many more. A CD-ROM is a metallic disc bounded on a polycarbonate plastic base and coated with the transparent protective layer. A track spirals from the centre and ends on the outer edge and generally three miles long. These are 16,000 tracks per inch.

It has generally 660 MB of data storage capacity, while floppy has a capacity of 1.44 MB. A12-cm diameter can store up to 2,50,000 A4 pages of text approximately or 85 minutes of full-screen video or sound. It can store combinations of images, sound, text, video, graphics and animations. A new development in the CD-ROM technology is Multi-layered Digital Versatile Disc (DVD) with still high storage capacity which people are already using.