a method of processing a plurality of different code systems for an information processing apparatus including an operating system , comprises a step of inputting a source program , and a compiling step of analyzing meaning of the source program to thereby create a series of instructions and data required for executing a processing equivalent to the meaning of the source program . the compiling step includes a sub - step of transforming character type constants to a first code system occupying region including a first number of bits and transforming character string constants to a second code system occupying a region including a number of bits which is equal to product of a sum of the number of characters of the character string constants plus one and multiplied with the first bit number so that character type variables designated in the source program correspond , respectively , to the region of the first bit number while a character type array corresponds to a region including a number of bits which is equal to a product resulting from multiplication of the first bit number with the number of elements of the array .