Fault-tolerant computers have been developed for applications that require a very high degree of hardware reliability, and it is frequently asked whether similar techniques can be brought to bear on software for critical applications, e.g., ascent guidance software on launch vehicles, launch-control software for ground computers, and control and command software. The principal techniques employed in hardware fault tolerance are seen to be applicable also through software fault tolerance: error detection, protective redundancy, and rollback provisions. Of course, they need to be implemented in a specific manner; particularly the redundancy must be provided by a different code than that used for the primary modules. The recovery block (proposed by Randell), with the addition of a watchdog timer, has been implemented in a number of skeleton routines and has been found quite suitable in connection with the established structure for spaceborne software. A reliability model is proposed that shows a very considerable reduction in failure probability even when the fault-tolerance provisions themselves are far from perfect. It is therefore believed that the time is quite ripe to undertake serious studies of fault-tolerant software for space applications. (Author).

Comprehensive coverage of all aspects of space application oriented fault tolerance techniques • Experienced expert author working on fault tolerance for Chinese space program for almost three decades • Initiatively provides a systematic texts for the cutting-edge fault tolerance techniques in spacecraft control computer, with emphasis on practical engineering knowledge • Presents fundamental and advanced theories and technologies in a logical and easy-to-understand manner • Beneficial to readers inside and outside the area of space applications

Recent advances in micro-electronics and in computer architecture have led to renewed interest in fault-tolerant computers for spacecraft applications. The general field of fault-tolerant computers is surveyed, and concepts of static and dynamic redundancy, error detection by code or multiple processing, and the significance of low-level redundancy are explained. Prior efforts in the design of fault-tolerant computers for space applications are surveyed with processing capability, weight, and reliability estimates listed for a number of representative efforts. The SAMSO Fault-Tolerant Spaceborne Computer (FTSC) is the most current of these developments, and it is described in greater detail together with the proposed reliability test methodology for the prototype. Recent developments in reliability estimation, employment of microprocessors, and fault-tolerant software that are related to this field are briefly discussed. (Author).

Computers are currently used in a variety of critical applications, including systems for nuclear reactor control, flight control (both aircraft and spacecraft), and air traffic control. Moreover, experience has shown that the dependability of such systems is particularly sensitive to that of its software components, both the system software of the embedded computers and the application software they support. Software Performability: From Concepts to Applications addresses the construction and solution of analytic performability models for critical-application software. The book includes a review of general performability concepts along with notions which are peculiar to software performability. Since fault tolerance is widely recognized as a viable means for improving the dependability of computer system (beyond what can be achieved by fault prevention), the examples considered are fault-tolerant software systems that incorporate particular methods of design diversity and fault recovery. Software Performability: From Concepts to Applications will be of direct benefit to both practitioners and researchers in the area of performance and dependability evaluation, fault-tolerant computing, and dependable systems for critical applications. For practitioners, it supplies a basis for defining combined performance-dependability criteria (in the form of objective functions) that can be used to enhance the performability (performance/dependability) of existing software designs. For those with research interests in model-based evaluation, the book provides an analytic framework and a variety of performability modeling examples in an application context of recognized importance. The material contained in this book will both stimulate future research on related topics and, for teaching purposes, serve as a reference text in courses on computer system evaluation, fault-tolerant computing, and dependable high-performance computer systems.

"This book increases awareness of the need for application-level fault-tolerance (ALFT) through introduction of problems and qualitative analysis of solutions"--Provided by publisher.