Unlike natural languages, programming languages are strictly stylized entities created to facilitate human communication with computers. In order to make programming languages recognizable by computers, one of the key challenges is to describe and implement language syntax and semantics such that the program can be translated into machine-readable code. This process is normally considered as the front-end of a compiler, which is mainly related to the programming language, but not the target machine. This article will address the most important aspects in building a compiler front-end; that is, syntax and semantic analysis, including related theories, technologies and tools, as well as existing problems and future trends. As the main focus, formal syntax and semantic specifications will be discussed in detail. The article provides the reader with a high-level overview of the language implementation process, as well as some commonly used terms and development practices.