This report describes the APL (Accountable unit, Program, and line item) budget system, a computerized three-dimensional program budget system that has been implemented in the Cambridge (Massachusetts) School Department. Various chapters discuss the differences between traditional budgeting and program budgeting, present an overview of te APL system, describe the implementation of the APL system in the Cambridge School Department, and provide an indepth analysis of the APL system and some of the difficulties encountered during its implementation at Cambridge. A glossary of important terms and sample budget forms and output budget reports for the APL system are included in the appendix. (JG)