The emergence of low cost microprocessor and minicomputer technology and the increasing functional density of integrated circuits has made it practical to apply advanced general purpose operating systems to small laboratory computing systems. The desirability of automating materials testing laboratories has increased because of the successes achieved in reducing man-hours per test, improving data accuracy, and program flexibility to handle complex tests. Instron has developed a system based on the software executive RSX-11M (trademark of Digital Equipment Corporation) which is capable of controlling many laboratory instruments, and can be built in a modular fashion, from a small dedicated system to a large distributed processing network. The system depends on microprocessor-controlled interface modules for efficient data acquisition and control. These interface modules are serviced by a flexible device driver, which forms an interface between the hardware and the application programming language, commonly FORTRAN IV, Interpretive BASIC, or Compiled BASIC. The use of the RSX-11M multitasking operating system means that many instruments can be serviced easily. Instruments such as servohydraulic testing instruments which have requirements of complex real-time control, substantial data reduction, and data reporting can be serviced by several tasks running at different priorities. Control tasks thus take precedence over data reduction tasks. A feature of the system in larger configurations is the use of distributed processing units (DPUs) as front-end concentrators performing detailed control of a small number of instruments. Several such DPUs may be connected to the central processor to form a star network. A great advantage of this system is the ease with which it can grow to meet the advancing needs of the laboratory.