Magic number

A magic number is a number that is explicitly defined in the code of a computer program without detailing its purpose. The use of uncommented magic numbers is a sign of a poor programming style. An exception is signatures used to identify a specific object. For example, all files in PNG format begin with the constant 89 50 4E 47 0D 0A 1A 0A, which corresponds to the hexadecimal equivalent of the text string “.PNG…”