Kops Make Great Theft Prevention Experts is a mnemonic for prefixes from SI units. The theme of this mnemonic is NetHack. An SI unit, such as a metre, gram, litre, or newton, can have a prefix attached to represent a power of ten, such as 1,000. For example, a kilometre (km) is 1,000 metres, a megagram (Mg) is 1,000,000 grams, a gigalitre (GL) is 1,000,000,000 litres. This has applications in computing also: a kilobyte is varingly 1,000 or 1,024 bytes. (The number 1,024 is 2 to the 10th power; a megabyte would have 2 to the 20th power bytes.)