[ $T_EX$ ] is a typesetting system created by Donald E. Knuth for producing publication-quality scientific books and journals. It is famous for the line breaking algorithm, the formatting of complex mathematical formula, and the powerful macro programming capability. Recently $T_EX$ plays a new role of an automatic typesetting engine. The paper describes $T_EX$ in the framework of typography by comparing with DTP softwares and word processors.