Book excerpt: Basic operations. Applications of nonlinear devices. Function fitting. Function generation. Instruments and data acquisition. Communications and signal processing. Computing and control. Understanding nonlinear circuits. About logarithmic circuits. About multipliers. About dividers. About nonlinear integrated circuits. Discontinuous approximations. Multifunction devices: powers & roots. Root mean-square. Aids for the designer. Log-circuits applications. Log ratio applications. Antilog applications. Multiplying and squaring.