Information Hiding

The information hiding principle, which played a central role in Monads and now in SPEEDOS, was described by Prof. David L. Parnas in three extremely significant and influential papers which were published around 1970 [4, 5, 6]. Interestingly a similar concept formed the basis of the modules (called "subsystems") of the ICL2900 VME-B operating system, the design of which began around the same time, and on which Prof. Keedy had worked as a design team member [7, 8].