A programing language, called APDL (Algorithmic Processor Description Language), is developed for describing the behavior of digital computer processors irrespective of their eventual implementation. ALGOL 60 is used as a base language and several features are added including: (1) register data types and operators to allow the convenient and accurate description of the register computations which occur in all processors, (2) "time blocks" to permit the specification of the delays involved in operations, and (3) "if ever statements" to allow the description of parallel operations. Programs are presented for compiling a description into a subset of ALGOL for simulation and for translating it into a hardware specification for actual implementation. The hardware specification consists of a list of hardware elements, a table of interconnections among the elements, and a state table description of a controller that will sequence the flow of data through the hardware network. A small existing computer is described at several levels in the language, the processor is simulated and implemented at each level, and finally the performance of the programs is evaluated. A list of references, the precedence grammar for APDL, and sample listings are appended to the report. (Author/JY)