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 opcode, offset operand and length operand 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 operand to the first program count; (c) storing a second instruction, which is located at a position a value of the length operand from the second program count in the code memory, in a second buffer; (d) replacing the second instruction in the code memory with a third instruction, which is not recognized by a microprocessor as an instruction in the microprocessor instruction set; (e) sequentially executing instructions beginning with an instruction corresponding to the second program count; (f) replacing the third instruction in the code memory with the second instruction stored in the second buffer when an error occurs while the third instruction is being executed; and (g) changing a current program count of the code memory to a program count of the code memory, which is obtained by adding one unit to the first program count stored in the first buffer.