The book addresses ways and means of organizing computations, highlighting the relationship between algorithms and the basic mechanisms and runtime structures necessary to execute them using machines. It completely abstracts from concrete programming languages and machine architectures, taking instead the lambda calculus as the basic programming and program execution model to design various abstract machines for its correct implementation.

The emphasis is on fully normalizing machines based on full-fledged beta-reductions as essential prerequisites for symbolic computations that treat functions and variables truly as first-class objects. Their weakly normalizing counterparts are shown to be functional abstract machines that sacrifice the flavors of full beta-reductions for decidedly simpler runtime structures and improved runtime efficiency. Further downgrading of the lambda calculus leads to classical imperative machines that permit side-effecting operations on the runtime environment.

本书讨论了组织计算的方式和方法，强调了算法与使用机器执行它们所需的基本机制和运行时结构之间的关系。它完全从具体的编程语言和机器结构中抽象出来，而是将λ微积分作为基本的编程和程序执行模型，为其正确的执行设计各种抽象的机器。

重点是基于成熟的β-还原的完全规范化机器，作为将函数和变量真正视为第一类对象的符号计算的必要前提。它们的弱规范化对应物被证明是功能性的抽象机器，它们牺牲了完整的β-还原的味道，以换取绝对简单的运行时结构和改进的运行时效率。lambda微积分的进一步降级导致了经典的命令式机器，它允许对运行时环境进行副作用的操作。