Direct execution lisp and cell memory

Lisp is the second oldest programming language in use today. It was treated as a special language for AI applications until the recent trend towards symbolic processing. The advantages of Lisp in processing symbols sometimes are outweighted by the inefficient implementations. This paper presents a direct execution approach in implementing Lisp. The concept of direct execution is explained. The Lisp execution environment is analyzed. The cell memory architecture is presented as the efficient solution for direct execution Lisp. This memory structure reduces the number of bits required for implementing garbage collection algorithm and the number of memory cycles for Lisp programs. Several examples are given to elaborate the direct execution concept and the advantages of cell memory. This direct execution Lisp machine has built-in functions such as interrupt and I/O which are major functions for real-time application.