1. A method of reducing the size of a program in a code memory, comprising: (a) storing a first program count of a first instruction in a first buffer when an error occurs while the first instruction having an Operand including Offset and Length is being executed among a plurality of instructions loaded in the code memory; (b) changing a current program count of the code memory to a second program count which is obtained by adding the Offset to the first program count; (c) storing a second instruction, which is located at a position shifted from the second program count by a value of the Length, in a second buffer; (d) replacing the second instruction with a third instruction, which is not recognized by a microprocessor; (e) replacing the third instruction with the second instruction stored in the second buffer when an error occurs while the third instruction is being executed; and (f) changing the current program count of the code memory to a predetermined program count next to the first program count stored in the first buffer.