The Environmental Data Coding Specification (EDCS) is a mapping between data and meaning. Data in a system may need to be identified as to purpose, metric, and usage. This specification defines a standard set of terms for providing this information.
Access to the codes defined by this specification is through an application programming interface (API). The abstract specification of this API is defined in ISO/IEC 18025. Each part of ISO/IEC 18041 defines the binding of that abstract specification to a particular programming language. The purpose of this part of ISO/IEC 18041 is to define a standard binding for the C computer programming language.
http://standards.iso.org/ittf/PubliclyAvailableStandards/ISO_IEC_18041-4_Ed2.html