1. A function generator for an arbitrarily specifiable function comprising: (a) an oscillator; (b) an address counter having its input coupled to the output of said oscillator; (c) a storage matrix with 2.sup.n address locations each capable of storing m bits the number m of said bits being determined by the maximum change in value of the function between two adjacent addresses, the data stored at each address being only the change in value from the previous adjacent address, said storage matrix receiving its address input from said counter; (d) a bidirectional counter; (e) means to drive said bidirectional counter with a frequency higher by a factor of 2.sup.m-1 than the frequency driving the address counter; (f) a digital to analog converter receiving its input from said bidirectional counter and providing the function generator output in analog form; and (g) a control member, having as an input an external measurement variable for coupling the stored values in said storage matrix sequentially to said integrating means only up to an address dependent on said external measurement coupled so as to control the input to said integrating means.