This appendix discusses number formats used in digital audio. They are divided into ``linear'' and ``logarithmic.'' Linear number systems include binary integer fixed-point, fractional fixed-point, one's complement, and two's complement fixed-point. The -law format is a popular hybrid between linear and logarithmic amplitude encoding. Floating-point combines a linear mantissa with a logarithmic ``exponent,'' and logarithmic fixed-point can be viewed as a special case of floating-point in which there is no mantissa. This appendix does not cover audio coding methods such as MPEG (MP3) [5,7,51,6] or Linear Predictive Coding (LPC) [12,41,42].