This document builds upon ISO/IEC 14882 by describing requirements for implementations of an interface that computer programs written in the C++ programming language could use to invoke algorithms with concurrent execution. The algorithms described by this document are realizable across a broad class of computer architectures. This document is written as a set of differences from the base standard.

Some of the functionality described by this document might be considered for standardization in a future version of C++, but it is not currently part of ISO/IEC 14882:2020. Some of the functionality in this document might never be standardized, and other functionality might be standardized in a substantially different form.

The goal of this document is to build widespread existing practice for concurrency in the ISO/IEC 14882:2020 algorithms library. It gives advice on extensions to those vendors who wish to provide them.