This document provides an overview of the Wiselib, an open-source C++ template library for programming heterogeneous Internet of Things (IoT) platforms. The Wiselib allows for writing portable code that can compile and run on various hardware platforms. It includes reusable implementations of common algorithms, abstracts away differences in operating systems, and provides platform-independent data structures and utility functions. The document outlines key aspects of the Wiselib like its architecture, usage scenarios, callback mechanism, message serialization, and supported programming environments.