Because of their simplicity, interpreters are often employed early on as a proof of concept, to be later replaced by compiled languages. Nevertheless, some applications, such as the BSD packet filters (Subsection 3.5.4) and Java applets (Subsection 3.5.5) over the world wide web (WWW), exploit interpreter characteristics in areas where speed matters.
First, we look at techniques that have been developed to speed-up interpretation (Subsection 3.5.1). Since most interpreters use a (virtual) stack machine to execute the programs, we look at work done on implementing stack machines in Subsection 3.5.2. Many of the interpretation techniques made their first appearance in Forth systems. We look at Forth in Subsection 3.5.3. In Subsection 3.5.4 and 3.5.5 we look at uses of interpreters in the BSD packet filter and in Java.