Gigabytes

Consumer confusion

Since the first disk drive, the IBM 350, disk drive manufacturers expressed hard drive capacities using decimal prefixes. With the advent of gigabyte-range drive capacities, manufacturers labelled many consumer hard drive, solid-state drive and USB flash drive capacities in certain size classes expressed in decimal gigabytes, such as "500 GB". The exact capacity of a given drive model is usually slightly larger than the class designation. Practically all manufacturers of hard disk drives and flash-memory disk devices continue to define one gigabyte as 1000000000bytes, which is displayed on the packaging. Some operating systems such as Mac OS X, iOS, Android, Ubuntu, and Debian express hard drive capacity or file size using decimal multipliers, while others such as Microsoft Windows (including Windows Phone) report file size using binary multipliers. This discrepancy causes confusion, as a disk with an advertised capacity of, for example, 400 GB (meaning 400000000000bytes, equal to 372 GiB) might be reported by the operating system as "372 GB".