The data stored on a stack when an error occurs during execution of a program is not removed for next step operation so that a user can discriminate a cause of an error easily. The method includes the steps: (A) storing input data on corresponding level of a stack (4) and sending input data to an arithmatic logic unit (ALR,2) storing output data of an ALU (2) on a stack (4), and storing level number of current stack (4), coefficient, local variable, result of function operation on corresponding frame of a circular que (5), a function unit, a local variable unit, an execution result storing unit respectively; and (C) quitting the step (B) and checking execution trace data by analyzing data stored on a circular cue (5) when an error occurs during the step (B).
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