Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In the modern Royal Navy, and other navies of Europe and the Commonwealth, ships are identified by pennant numbers (sometimes referred to as pendant numbers). The name pennant number arises from the fact that ships were originally allocated a pennant (flag) identifying a flotilla or particular type of vessel: for example, in the Royal Navy, the red burgee for torpedo boats, H for torpedo boat destroyers. By the addition of a number to the identifying pennant, each ship could be uniquely identified. A pennant number thus consists of letters and numbers. Where a letter precedes a number it is known as a flag superior and where it is a suffix it is known as a flag inferior. Not all pennants have a flag superior.