Safety is the foremost need that every human being desires irrespective of the impact of the breach of safety. As today software is associated with almost every field whether it be education or aerospace, so system demands more and better safety systems and mechanisms. Any system whose failure can catastrophically impact human lives, environment and equipment can be called as safety critical system. These kinds of risks are handled using safety engineering techniques elaborated in this paper. In this paper, the authors have discussed about safety critical systems, their specifications and standards, language support and approaches of designing safety critical systems.