SISC is an extensible Java based interpreter of the algorithmic language Scheme. SISC uses modern interpretation techniques, and handily outperforms all existing JVM interpreters (often by more than an order of magnitude).

In addition, SISC is a complete implementation of the language. The entire R5RS Scheme standard is supported, no exceptions. This includes a full number tower including complex number support, arbitrary precision integers and floating point numbers, as well as hygienic R5RS macros, proper tail recursion, and first-class continuations (not just the escaping continuations as in many limited Scheme systems). SISC also attempts to implement the standard as correctly as possible, while still providing exceptional performance.