An Overview of the ISPL Computer System Design
This paper explores the advantages of the concurrent
design of the language, operating system, 
and machine (via microcode) to create an interactive programming
laboratory.  It describes the synergistic 
effect that the freedom to move and alter features from
one of these domains to another has had on the 
design of this system (which has not been implemented).
 This freedom simplified both incremental compilation 
and the system's addressing structure, and centralized the
communication mechanisms enabling the construction 
of hierarchical subsystems.  It also suggested an important
new concept for operating systems: separation 
of the scheduling from the maintenance functions in resource
allocation. This separation enables incorporation 
of new scheduling algorithms (decision of what to do) without
endangering the system integration (correctly 
performing the scheduling decisions).
CACM February, 1973
Balzer, R. M.
