Different program slicing methods are used for debugging, testing, reverse engineering and maintenance. Slicing algorithms can be classified as static slicing and dynamic slicing methods. In applications such as debugging the computation of dynamic slices is more preferable since it can produce more precise results. In this paper we introduce a new forward global method for computing dynamic slices of C programs. In parallel to the program execution the algorithm determines the dynamic slices for any program instruction. We also propose a solution for some problems specific to the C language (such as pointers and function calls). The main advantage of our algorithm is that it can be applied to real size C programs, because its memory requirements are proportional to the number of different memory locations used by the program (which is in most cases far smaller then the size of the execution history - which is, in fact, the absolute upper bound of our algorithm).