The intent of this standard is to define VHDL accurately. Its primary audiences are the implementor of tools 5 supporting the language and the advanced user of the language. Other users are encouraged to use commercially available books, tutorials, and classes to learn the language in some detail prior to reading this manual. These resources generally focus on how to use the language, rather than how a VHDL-compliant tool is required to behave. At the time of its publication, this document was the authoritative definition of VHDL. From time to time, it may become necessary to correct and/or clarify portions of this standard. Such corrections and clarifications may be published in separate documents. Such documents modify this standard at the time of their publication and remain in effect until superseded by subsequent documents or until the standard is officially revised.