Ababaw Tilahun (PhD)Demelash Smegnsh2018-07-182023-11-042018-07-182023-11-042016-07http://etd.aau.edu.et/handle/123456789/9120A D-module is a module over a ring of Di_erential Operators. The major interest of such D-modules is as an approach to the theory of linear partial di_erential equations. Algebraic D-modules are modules over the Weyl algebra An over the _eld C of complex numbers. The main purpose of this thesis to work on the A3=module C[x;y;z]_; where _ is the product of linear forms. In this thesis we computed the decomposition factors and hence the length of A3 -module C[x; y; z]_ using the method of partial fractions of rational functionsenOn the length of D-modules overThesis