Abstract The Shuttle ground operations simulator (SGOS) simulation software introduced in this paper is used to train NASA ground controllers and to certify launch countdown readiness. The SGOS executive and its subsystems have been an integral component of the Shuttle Launch Safety Program for almost 30 years. It is usable (via a LAN) by over 2000 NASA employees at the Kennedy Space Center and 11 000 contractors. SGOS supports over 800 models comprised of several hundred thousand lines of code and over 1000 Model Control Procedures. Copyright © 2007 John Wiley & Sons, Ltd.

The goal of the project was to design and implement an English word-list representation suitable for spell-checking in space-constrained environments. The compression algorithm was derived by statistically analyzing the word list. A compression ratio of 18% was achieved through a combination of prefix and suffix encoding. The compressed file can be randomly accessed by prefix marker positions. A simple spell-checker based on the encoding was implemented and tested in Java. Copyright © 2005 John Wiley & Sons, Ltd.

We propose a novel multicast protection scheme based on a dual-homing architecture where each destination host is connected to two edge routers. Under such an architecture, the two paths from the source of the multicast session to the two edge routers provide certain protection for the data traffic from the source to the destination host. Two problems are associated with the proposed dual-homing multicast protection scheme. One is to calculate the individual survivability for a destination host that is connected to two edge routers. The other is to assign two edge routers for each destination host such that the total survivability is maximized for the multicast session subject to the port number constraint of edge routers. We propose an optimal algorithm to solve the first problem and a heuristic algorithm to solve the second problem. Through simulations, we show that the proposed heuristic algorithm achieves a performance close to the calculated lower bound.

A static analysis of the instructions used to implement all of the system software on the Lilith computer is described. The results are compared to those of a similar analysis performed on the Mesa instruction set architecture. The data provide a good illustration of how code generation strategies and language usage can affect opcode statistics, even for machines with similar architectures.>

Abstract This paper describes the design and implementation of a kernel for the distributed programming language StarMod. The distributed programming kernel was written in a subset of StarMod supported by a concurrent programming kernel. Kernel issues addressed include process representation, I/O device management, signal semantics, system utilities, network communication and the implementation of high‐level language communication primitives. We conclude with a summary of our experiences in the development of a ‘bare machine’ kernel for a network of microprocessors.

We are concerned with languages in which the programmer has explicit control over the referencing environment of a name. Several modern programming languages, including Ada, Euclid, Mesa, and Modula, implement these control capabilities. This paper describes a simple technique which uses the traditional concepts of a hashed symbol table and lexical level to solve many of the symbol table implemen-tation problems associated with explicit scope control. The primary ad-vantage of this technique is that a single symbol table abstraction can be used to simply and efficiently solve most problems in scope control.

MCODE is a high-level language, stack machine designed to support strongly-typed, Pascal-based languages with a variety of data types in a modular programming environment. The instruction set, constructed for efficiency and extensibility, is based on an analysis of 120,000 lines of Pascal programs. The design was compared for efficiency with the instruction sets of the Digital Equipment PDP-11 and VAX by examining the generated code from the same compiler for all three machines. In addition, the original design choices were tested by analyzing the generated code from 19,000 lines of StarMod programs. As a result of this iterative experiment, we have summarized our observations in an efficient reorganization of the VAX's addressing modes.

Abstract More than 120,000 lines of Pascal programs, written by graduate students and faculty members, have been statically analysed to provide a better understanding of how the language is ‘really’ used. The analysis was done within twelve distinct contexts to discover differences in usage patterns among the various contexts. For example, it was found that 47 per cent of the operands in arguments lists were constants. The results are displayed as tables of frequency counts which show how often each construct is used within a context. Also, we have compared our findings to the results from studies of other languages, such as FORTRAN, SAL and XPL.

Distributed programming is characterized by high communications costs and the inability to use shared variables and procedures for interprocessor synchronization and communication. *MOD is a high-level language system which attempts to address these problems by creating an environment conducive to efficient and reliable network software construction. Several of the *MOD distributed programming constructs are discussed as well as an interprocessor communication methodology. Examples illustrating these concepts are drawn from the areas of network communication and distributed process synchronization.