As of 2007, most consumer hard drives are defined by their gigabyte-range capacities. The true capacity is usually some number above or below the class designation. Although most manufacturers of hard disks and Flash disks define 1 gigabyte as 1,000,000,000 bytes, the computer operating systems used by most users usually calculate a gigabyte by dividing the bytes (whether it is disk capacity, file size, or system RAM) by 1,073,741,824. This distinction is a cause of confusion, especially for people from a non-technical background, as a hard disk with a manufacturer rated capacity of 40 gigabytes may have its capacity reported by the operating system as only 37.2 GB, depending on the type of report.
