Computer Science Programming Basics in Ruby

2.3 Scales of Magnitude

Mass storage devices and memories are very large and thus measured with units that have names different from those used in everyday life. While we use the colloquial word grand to refer to $1,000, for amounts greater than $1,000 we use the names of the decimal system, such as million. These are not universally used—in the United States, one thousand million is called billion; in Europe it is called milliard. There is, however, an agreed upon nomenclature for powers of 10 so that one thousand is called kilo, one million is called Mega, and so on (see Table 2-1). Note the lowercase in kilo, the uppercase in Mega, and all that follow. This comes from the fact that the letter K is reserved, in the decimal nomenclature, for the designation of the absolute temperature measure (degrees in Kelvin).^[1]

Table 2-1. Scales of magnitude

Units	Actual size (bytes)	Other names	Real-world quantities
Megabyte (MB)	1,000,000	Million, 106	The King James version of the Bible contains approximately 5 million characters.
Mebibyte (MiB)	1,048,576	220	The speed of light is 300 million meters/second.
Gigabyte (GB)	1,000,000,000	Billion, 109	At 5% interest, $1 billion would return $50,000,000/year.
Gibibyte (GiB)	1,073,741,824	230	A billion $1 bills, end to end, would wrap the Earth at the equator 4.5 times.
Terabyte (TB)	1,000,000,000,000	Trillion, 1012	The U.S. GDP for 2006 was $13 trillion.
Tebibyte (TiB)	1,099,511,627,776	240	Global GDP in 2006 was estimated by the World Bank ...