1491	 EULER A Generalization ALGOL and its Formal Definition Part I	 A method for defining programming languages is developed which introduces a rigorous relationship between structure and meaning. The structure of a language is defined by a phrase structure syntax the meaning in terms of the effects which the execution of a sequence of interpretation rules exerts upon a fixed set of variables called the Environment. There exists a one-to-one correspondence between syntactic rules and interpretation rules is determined by the sequence of corresponding syntactic reductions which constitute a parse. The individual interpretation rules are explained in terms of an elementary an d obvious algorithmic notation. A constructive method for evaluating a text is provided and for certain decidable classes of languages their unambiguity is proved. As an example a generalization of ALGOL is described in full detail to demonstrate that concepts like block-structure procedures parameters etc. can be defined adequately and precisely by this method.
