The principles of operation of nonlinear-interpolating-function generators are described. Nonlinear interpolators (n.l.i.s) comprise a plurality of nonlinear interpolating branches producing the desired output signal at a common output connection. The theory of the design of a simple halfsquarer is given, including a detailed consideration of both static and dynamic accuracy. N.L.I. squarers have an important application in n.l.i. multipliers, whose theory is explained.N.L.I.s provide simple function generators of good accuracy, fast response and excellent stability under ambient-temperature changes.A simple n.l.i. halfsquarer, using only two input branches, was found to have an overall low-frequency accuracy of ±0.7% of full output over a temperature range of 15–50degC, and a frequency response 2dB down, at 1 Mc/s. The provision of additional input branches improves the accuracy.