A two-dimensional input/output system for a massively parallel SIMD computer system providing an interface for the two-way transfer of data between a host computer and the SIMD computer. A plurality of buffers equal in number, and distributed with the individual processing elements of the SIMD computer are used to provide a temporary storage area which allows data in different formats to be mapped in a format suitable for transfer to the host computer or for transfer to the SIMD processing elements. The temporary storage is controlled in such a way as to transfer entire blocks of data in a single SIMD system clock cycle thereby achieving an input/output data rate of N bits/cycle for a SIMD computer consisting of N processors. The system is capable of handling irregular as well as regular data structures. The system also emphasizes a distributed approach in having the input/output system divided into N pieces and distributed to each processor to reduce the wiring complexity while maintaining the I/O rate.