The invention is a method for use in executing portable virtual machine computer programs under real-time constraints. The invention includes a method for implementing a single abstract virtual machine execution stack with multiple independent stacks in order to improve the efficiency of distinguishing memory pointers from non-pointers. Further, the invention includes a method for rewriting certain of the virtual machine instructions into a new instruction set that more efficiently manipulates the multiple stacks. Additionally, using the multiple-stack technique to identify pointers on the run-time stack, the invention includes a method for performing efficient defragmenting real-time garbage collection using a mostly stationary technique. The invention also includes a method for efficiently mixing a combination of byte-code, native, and JIT-translated methods in the implementation of a particular task, where byte-code methods are represented in the instruction set of the virtual machine, native methods are written in a language like C and represented by native machine code, and JIT-translated methods result from automatic translation of byte-code methods into the native machine code of the host machine. Also included in the invention is a method to implement a real-time task dispatcher that supports arbitrary numbers of real-time task priorities given an underlying real-time operating system that supports at least three task priority levels. Finally, the invention includes a method to analyze and preconfigure virtual memory programs so that they can be stored in ROM memory prior to program.