1. In a digital computer, a method of transforming a relatively high level source language statement into first, second, and third sets of relatively low level object language instructions such that instructions of said first set are executable in an interleaved fashion with instructions of said second and third sets both of which are executable at the same time, said method including the steps of: generating, via said computer, an instruction of said first set which specifies a mathematical operation in said statement and references two encoded addresses having the same code indicating that the respective addresses are of instructions in said second and third sets; and producing, via said computer, said instructions of said second and third sets for respective storage at said encoded addresses which are simultaneously executable to compute respective addresses for two variables in said statement that are modified by said mathematical operation.