Describes Ports, a unified method for communication between a computer program and terminals, files, peripheral devices, other programs, and supervisory software. In ISPL (Incremental System Programming Language, described in R-563), each job has a Port named MONITOR that handles resource allocation: creating and deleting files, assigning file space, core space, processor time. This design permits a hierarchical system of monitors, each controlling the jobs running under it. By routing output to a user terminal, Ports enables online debugging and simulation of rewritten files of programs. The Port concept improves modularity in three ways: (1) Each connection need not be specified by the programmer but can be decided at execution. (2) Linkage between programs is co-routine rather than subroutine, which simplifies programming, retains context, and removes the need for hierarchical organization. (3) With different connections via Ports, the same system can be used in many ways, e.g., online or off, in simulation mode, audit-trailed, or data breakpointed. (See also R-562, R-603, R-622, RM-5611.)
This report is part of the RAND Corporation Report series. The report was a product of the RAND Corporation from 1948 to 1993 that represented the principal publication documenting and transmitting RAND's major research findings and final research.
Our mission to help improve policy and decisionmaking through research and analysis is enabled through our core values of quality and objectivity and our unwavering commitment to the highest level of integrity and ethical behavior. To help ensure our research and analysis are rigorous, objective, and nonpartisan, we subject our research publications to a robust and exacting quality-assurance process; avoid both the appearance and reality of financial and other conflicts of interest through staff training, project screening, and a policy of mandatory disclosure; and pursue transparency in our research engagements through our commitment to the open publication of our research findings and recommendations, disclosure of the source of funding of published research, and policies to ensure intellectual independence. For more information, visit www.rand.org/about/principles.
The RAND Corporation is a nonprofit institution that helps improve policy and decisionmaking through research and analysis. RAND's publications do not necessarily reflect the opinions of its research clients and sponsors.