A lucid statement of the philosophy of modular programming can be found in a 1970 textbook on the design of system programs by Gouthier and Pont [1, l Cfl0. 23], which we quote below: A well-defined segmentation of the project effort ensures system modularity. Each task fonos a separate, distinct program module. At implementation time each module and its inputs and outputs are well-defined, there is no confusion in the intended interface with other system modules. At checkout time the in tegrity of the module is tested independently; there are few sche duling problems in synchronizing the completion of several tasks before checkout can begin. Finally, the system is maintained in modular fashion; system errors and deficiencies can be traced to specific system modules, thus limiting the scope of detailed error searching. Usually nothing is said about the criteria to be used in dividing the system into modules. This paper will discuss that issue and, by means of examples, suggest some criteria which can be used in decomposing a system into modules. A Brief Status Report The major advancement in the area of modular programming has been the development of coding techniques and assemblers which (1) allow one modu1e to be written with little knowledge of the code in another module, and (2) alJow modules to be reas sembled and replaced without reassembly of the whole system.

Algorithms for Computer Algebra is the first comprehensive textbook to be published on the topic of computational symbolic mathematics. The book first develops the foundational material from modern algebra that is required for subsequent topics. It then presents a thorough development of modern computational algorithms for such problems as multivariate polynomial arithmetic and greatest common divisor calculations, factorization of multivariate polynomials, symbolic solution of linear and polynomial systems of equations, and analytic integration of elementary functions. Numerous examples are integrated into the text as an aid to understanding the mathematical development. The algorithms developed for each topic are presented in a Pascal-like computer language. An extensive set of exercises is presented at the end of each chapter. Algorithms for Computer Algebra is suitable for use as a textbook for a course on algebraic algorithms at the third-year, fourth-year, or graduate level. Although the mathematical development uses concepts from modern algebra, the book is self-contained in the sense that a one-term undergraduate course introducing students to rings and fields is the only prerequisite assumed. The book also serves well as a supplementary textbook for a traditional modern algebra course, by presenting concrete applications to motivate the understanding of the theory of rings and fields.

Now in an updated second edition, this classroom-tested textbook covers fundamental and advanced topics in orbital mechanics and astrodynamics designed to introduce readers to the basic dynamics of space flight. The book explains concepts and engineering tools a student or practicing engineer can apply to mission design and navigation of space missions. Through highlighting basic, analytic, and computer-based methods for designing interplanetary and orbital trajectories, the text provides excellent insight into astronautical techniques and tools. The second edition includes new material on the observational basics of orbit determination, information about precision calculations for data used inflight, such as Mars 2020 with the Ingenuity Helicopter, and improvements in mission design procedures, including the automated design of gravity-assist trajectories. Orbital Mechanics and Astrodynamics: Techniques and Tools for Space Missions is ideal for students in astronautical or aerospace engineering and related fields, as well as engineers and researchers in space industrial and governmental research and development facilities, as well as researchers in astronautics.