Abstract. K is a rewrite-based executable semantic framework in which programming languages, type systems, and formal analysis tools can be defined using configurations, computations and rules. Configurations organize the state in units called cells, which are labeled and can be nested. Computations are special nested list structures sequentializing computational tasks, such as fragments of program. K (rewrite) rules make it explicit which parts of the term they read-only, write-only, read-write, or do not care about. This makes K suitable for defining truly concurrent languages even in the presence of sharing. Computations are like any other terms in a rewriting environment: they can be matched, moved from one place to another, modified, or deleted. This makes K suitable for defining control-intensive features such as abrupt termination, exceptions or call/cc. This paper presents an overview of K Framework and the K tool, focusing on the interaction between the K tool and Maude.