定义的语言与以前的PL/I标准不同，尽管在源程序和语义级别上基本上是向上兼容的。附录A中总结了这些差异。规定了符合PL/I程序的语法和语义。仅根据这些一致性程序定义一致性处理器（或一致性实现）。定义是通过指定一个概念性的PL/I机器来完成的，该机器翻译和解释预期的PL/I程序。

The language defined is different from those of previous PL/I standards, although substantially upward compatible, at the source program and semantic level. The differences are summarized in appendix A. Specifies the syntax and semantics of conforming PL/I programs. Defines a conforming processor (or conforming implementation) only in terms of those conforming programs. The definition is accomplished by specifying a conceptual PL/I machine which translates and interprets intended PL/I programs.