This is Part I of a two-part article on Korean character processing by a computer. In part I, the problems in Korean character processing are identified and the theoretical foundation is laid out as a viable solution to them. The one-and two-dimensional syntactic structures of Korean characters are formally defined by means of BNF and " Patternal structure " respectively. Formal discussion of lexical and syntactic algorithms is given for character conversion. This character conversion algorithm is applicable to both input and output. For device-independence and implementation-independence, the concept of " cardinal symbol set " is introduced. We will present a historical survey of Korean character processing and discussion of implementation problems for the above algorithm In Part II.lgorithm In Part II.