Abstract: A process and apparatus (compiler program) carried out on a digital computer for converting a source program into an object program. The source program is entered into a first storage area of a computer. The symbolic source program is preferably first codified into computer executable code by the compiler program. The compiler program then examines each formula to determine whether it has been defined. If the first formula has been defined, it is removed from the first storage area; placed in a second storage area; and marked as being defined. if the first formula examined has not been defined, it is retained in the first storage area. The compiler program repeats this process for each formula in the first storage area. After the formulas in the first storage area have been examined, the compiler program determines whether any formulas have been added to the second storage area. If not, the process is stopped, indicating some error in programming.