Explain difference between Scanning and parsing.
Scanning and parsing: Scanning process is the process of recognizing the lexical components in a source string whereas parsing is the process of checking the validity of a source string, and to find out its syntactic structure. The purpose for separating scanning from parsing is that the lexical characteristics of a language can be specified by using Type-3 grammars. All Type-3 production identifies lexical components is also a Type-2 production. Conversely, a recognizer for Type-3 productions is easier, simple to build and more efficient throughout execution than a recognizer for Type-2 productions. Therefore it is better to handle the lexical and syntactic elements of a source language separately.