### Background

The first description of Scheme was written in 1975 [Scheme75]. A revised report [Scheme78] appeared in 1978, which described the evolution of the language as its MIT implementation was upgraded to support an innovative compiler [Rabbit]. Three distinct projects began in 1981 and 1982 to use variants of Scheme for courses at MIT, Yale, and Indiana University [Rees82], [MITScheme], [Scheme311]. An introductory computer science textbook using Scheme was published in 1984 [SICP].

As Scheme became more widespread, local dialects began to diverge until students and researchers occasionally found it difficult to understand code written at other sites. Fifteen representatives of the major implementations of Scheme therefore met in October 1984 to work toward a better and more widely accepted standard for Scheme.

Their report [RRRS] was published at MIT and Indiana University in the summer of 1985. Further revision took place in the spring of 1986 [R3RS], and in the spring of 1988 [R4RS]. The present report reflects further revisions agreed upon in a meeting at Xerox PARC in June 1992.

We intend this report to belong to the entire Scheme community, and so we grant permission to copy it in whole or in part without fee. In particular, we encourage implementors of Scheme to use this report as a starting point for manuals and other documentation, modifying it as necessary.