A parallel computer system prototype for CX-1 (Computer compleX), a shared-memory-type parallel processor array of MIMD type, was developed as a back-end processor to a medium-size main frame computer system FACOM M-340R. The target number of parallelism of CX-1 is 16, but the current prototype is limited to 4 processing units, 4 memory units and a central control unit. The parallel computer CX-1 was developed to achive fast computation with cheap computer cost by utilizing 16-bit microproceddor arrays, for the numerical solution of partial differential equations with multi-variables in multi-dimensional space. Described in this report are the basic design concept of CX-1, the details of its hardware and software developments, the resuts of testing and evaluation of the prototype system, and the results of two sample numerical practices.