Digital Formats

Floppy Disk, 5-1/4" 5.25-inch floppy disks are a magnetic data storage format with a flat circular plastic disk that has a magnetic coating (similar to magnetic tapes) inside a protective sleeve.  IBM released an 8-inch (203 x 203 x 1.6mm) flexible disk in 1972 which could store 80Kbytes of data.  ITC (Verbatim) commercialized a flexible 5.25-inch (133.3 x 133.3 x 1.6mm) floppy disk in 1978 that could store 160Kbytes, 360Kbytes, and then 1.2Mbytes by 1994.  There were other magnetic disk formats.  Sony discontinued floppy diskette production in 2011.

CD (compact disk) is a digital optical data storage format and was commercialized by Philips and Sony in 1982.  CDs are frequently used for audio content.  CDs are made from one disk of polycarbonate with metallized data layer just under the top labeling surface.  A laser follows a digital track recorded into the metallized layer and tracks are spaced 1.6um apart.  Care must be taken not to make impressions in the top labeling surface which can damage the data layer.  CDs measure 12cm (4.7-inches) diameter, 1.2mm (0.047-inches) thick, and have a 15mm diameter center hole.  CDs are becoming obsolete; car manufacturers have been phasing out CD players since before 2015.

DVD (digital video disk, digital versatile disk) is an optical data storage format commercialized in 1996 by Philips, Sony, Panasonic, Toshiba, Samsung, and others.  Commercial DVD-ROM (read only memory) disks became available in the U.S. in 1997 and Disney helped to promote the format by releasing movie content in 1998.  DVD-ROMs are constructed with tiny ‘data’ bumps molded into a polycarbonate disk, metallized, and the data layer covered with another polycarbonate disk.  A laser reads the metalized bumps by following a continuous spiral track that starts near the center of the disk and plays outward; tracks are spaced 0.740um apart.

Non-commercial recordable DVD formats were developed and Macrovision copyright protection and Region Code standards were adopted.  Pioneer commercialized the DVD-R and DVD-RW formats and released the first DVD recorder in late 1999 followed by Toshiba, Panasonic, Hitachi, and others.  The DVD-R format is the most universally compatible recordable DVD format and has a single session that must be ‘finalized’ in order to play in other machines. 

DVD+R and DVD+RW formats and recorders were commercialized by an alliance including Philips, Sony, and others in 2001.  DVD+ formats are multisession and can add material in multiple recording sessions before finalization.  The DVD+RW format was not officially recognized until 2008.  “RW” DVDs can be recorded and erased multiple times.  Early DVD players could not play all formats and standards as can most newer machines.  There are other DVD formats.

Non-commercial disks have the data recorded into an internal layer of dye by a laser; the data layer is located between two 0.6mm polycarbonate disks.  Standard DVDs are 12cm (4.7-inches) diameter and are 1.2mm (0.047-inch) thick.  DVDs have been mostly replaced by internet and cable content delivery and many computers have not had DVD drives since 2015.