This thesis describes two distinct, but mutually supportive, research projects. The first is the design and implementation of a high level language intended to be suitable for writing operating systems among other large software products. It provides facilities for the creation and control of asynchronous processes along with powerful data and "sequential" control structures. The second project is the design and implementation of a machine architecture which is a congenial host for modern block structured languages. This machine has several advantages compared to most of today's computers; code generation is simple, the object code is very compact and the machine is reasonably fast. Effective software systems are well designed, reliable, have "low" space-time products and are developed, maintained and used with a minimum amount of human effort. The work presented here is intended to be a viable first step towards the production of an environment for the production of effective software systems. / Science, Faculty of / Computer Science, Department of / Graduate