<> <> Numerical Analysis of Constrained Hamiltonian Systems and the Formal Theory of Differential Equations <> Mathematics and Computer in Simulation <> 45 (1998) 561-576 <> www.journals.elsevier.com/mathematics-and-computers-in-simulation <> doi.org/10.1016/S0378-4754(97)00129-8 <> This paper is written in a rather informal way and presents essentially my point of view of DAEs (at the time of writing), with special emphasis on constrained Hamiltonian systems. It is a write-up of my invited talk at the IMACS conference on Applications of Computer Algebra in Linz 1996. It shows how the formal theory provides a unifying framework for some physical and numerical aspects of such systems. The results are only preliminary and restricted to finite-dimensional systems. An extension to partial differential equations can be found in . <> journals <> postscript <> 1998 <> differential equation, Hamiltonian system, numerical integration <> differential equations, mathematical physics, numerical analysis <>