Wang, Doe-Ming creator Gupta, Gopal K. Chairperson Krisorn Jittorntrum Examination Committee Huynh, Ngoc Phien Examination Committee Ret-Ser Engineering Agency (R.O.C.) Scholarship Donor text series technical report th Bangkok Asian Institute of Technology 1980 continuing eng iv, 45 p. In recent year s, Chief Programmer Team, Top-Down Development, Structured Programming, and Development Support Library which represent the organization, design strategy, programming technique and supporting tool respectively have been treated as a hierarchical set of components in developing a reliable software system. In this study, Top-Down Development (in particular, the structure of modular programs as in Turner (1980)) and Development Support Library are studied. It is assumed that the pure tree structure is the best way to organize program modules when designing any software system. A software tool called PL/I Support System (PLISS) is designed and implemented to support the development of software system in pure tree structure. The application of Top-Down Development tends to proliferate the number of independently compiled modules that comprise the system and al so places certain demands on the language used for actual system implementation. These demands deal primarily with (1) specifying intermodule relationship; (2) propagating intermodule modification; and (3) Maintaining consistency in the realization of abstraction. In this thesis, we discuss the implications of these demands on a specific language PL/I. From this discussion the PL/I Support System based on a Programming Production Library is established. Finally, the elements and the functions of PL/I Support System are described. A thesis submitted in partials fulfilment of the requirements for the degree of Master of Engineering, School of Engineering and Technology Thesis (M.Eng.) - Asian Institute of Technology, 1980 PL/I (Computer program language) Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B21940 http://203.159.5.9/ait-thesis/detail.php?q=B21940 130598 20260818223503.0