Such sequences contain a string description delimited by double quotes ". The description is a sequence of character descriptions, where each of them is either just a character different from " and \, or is \ followed by either a, b, t, n, v, f, r, \, ", or one, two or three octal digits representing a natural number smaller than $256$ (in decimal, for example '\11' represents $9$), or an x followed by one or two hexadecimal digits (uppercase or lowercase, for example '\xA1' represents $161$).