J. Felix Costa (Lisbon) will discuss recent joint work with Manuel Campagnolo and Cris Moore on Analog Computation in Continuous Time. Abstract: We consider various extensions and modifications of Shannon's General Purpose Analog Computer, which is a model of computation by differential equations in continuous time. We show that several classical computation classes have natural analog counterparts, including the primitive recursive functions, the elementary functions, the levels of the Grzegorczyk hierarchy, and the arithmetical and analytical hierarchies.