A stack-based instruction set which includes two-operand, one-operand and zero-operand instructions is proposed, and is shown to produce a more compact code and fewer instructions for evaluating assignment statements than one-operand and zero-operand stack instruction sets. If this instruction set is then extended to include two-operand memory-to-memory instructions, the combined instruction set also produces more compact code than a simple memory-to-memory instruction set, for a set of "typical" assignment statements weighed by the frequency of their occurrence in real programs. Finally various alternatives for optimizing the proposed instruction set are discussed.