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Structure of directly executed languages: a new theory of interpretive system design

Technical Report ·
OSTI ID:5159542
This paper concerns two important issues in the design of optimal languages for direct execution in an interpretive system: binding the operand identifiers in an executable instruction unit to the arguments of the routine implementing the operator defined by that instruction, and binding operand identifiers to execution variables. These issues are central to the performance of a system, both in space and time. Historically, some form of ''machine language'' is used as the directly executable medium for a computing system. These languages traditionally are constrained to a single ''n-address'' instruction format; this constraint leads to an excessive number of ''overhead'' instructions that do nothing but move values from one storage resource to another being imbedded in the executable instruction stream. It is proposed to reduce this overhead by increasing the number of instruction formats available at the directly executed language level. Machine languages are also constricted with respect to the manner in which operands can be ''addressed'' within an instruction. Usually, some form of indexed base-register scheme is available, along with a direct addressing mechanism for a few, ''special'' storage cells (i.e., registers, and perhaps the zeroth page of main store). A different identification mechanism based on the Contour Model of Johnston is proposed. With this scheme, only N bits are needed to encode any identifier in a scope containing less than 2**N distinct identifiers. 11 figures, 2 tables, 32 references.
Research Organization:
Stanford Univ., Calif. (USA). Stanford Electronics Labs.
OSTI ID:
5159542
Report Number(s):
SU-326-P.39-27; SEL-77-048
Country of Publication:
United States
Language:
English