The design and implementation of an experimental A PL system on the small, sensor-based System/7 is described. Emphasis is placed on the solution to the problem of fitting a full APL system into a small computer. The system has been extended through an I/O auxiliary proces- sor to make it possible to use A PL in the management and con- trol of the System/7 sensor-based I/O operations. An APL interpreter and system for a small computer by M. Alfonseca, M. L. Tavera, and R. Casajuana System/?' is a small-size, special-purpose IBM computer for sen- sor-based applications. It has a limited memory of two to 64 kilo- words, 16 bits per word, not being byte-oriented. Its arithmetic unit includes an accumulator, one instruction address register, and seven work registers as well as several indicators. The cen- tral processing unit (CPU) is hardwired (not microprogrammed), with a fast cycle of 400 nanoseconds, and accepts up to about40 machine language instructions where bit and byte handling, fixed point multiplication and division, and all the floating point operations are absent. Only fixed point l6-bit integer numbers are supported. The standard peripheral equipment is likewise limited: small capacity disks (1.2 megawords)," a tape attachment, slow card reader and punch, matrix printer, and a teletype console. How- ever, telecommunication equipment and sensor-based input-out- put (I/O) equipment are available in large variety, including di- rect CPU attachment to other computer systems, and analog and digital input and output. Four levels of operation, with four complete arithmetic unit register sets, are supported in order to serve the different I/O interruptions. The computer was originally meant to be used primarily as an intelligent, sensor-controller terminal, connected to a host com- puter (e.g., the System/370 series) where the preprocessed data would be sent and further processed. Therefore, it was an- nounced with almost no stand-alone software, including only a 18 ALFONSECA, TAVERA, AND CASAJUANA IBM SYST J