SI units - prefixes

SI meets the Computer Age

• SI units are a little mixed up when used with storage
• When computer memory sizes were small, some people noticed that kilo (10^3) in SI units is close to 1024 (2^10). Spontaneously, many people started using kilo for 1024. This is a discrepancy of 2.4%. 
• Computer memory sizes grew and things got more mixed up. 3.5 inch floppies for instance had 1440 kilobytes, so someone made up the notation 1.44 megabytes. (1000 * 1024 - even more nonstandard SI)
• Gigabytes were even worse, they were interpreted differently depending on the manufacturer or software developer. Either 1000 * 1000 * 1000 bytes OR 1000 * 1000 * 1024.
• SI still hasn't handled this mess. IEEE (Institute or Electrical & Electronics Engineers) has sort of "taken over" the standards. In 1998, they released these standards. They aren't hugely used - things are still messed up.

Units

Binary Prefixes

 Further notes

• The "bi" portion at the end is pronounced "bee". 
• a 90 mm floppy disk should be described as having a capacity of 1.41 MiB (equivalent to 1.47 MB), not "1.44 MB" as labeled.
• 5 gigabytes (GB) should mean exactly 5 000 000 000 bytes, and 5 gibibytes (GiB) should mean exactly 5 368 709 120 bytes.