The Lexical analyzer is the first phase in compiler phases . In the lexical analyzer generator we automatically construct a lexical analyzer from a regular expression description of a set of tokens. construct a nondeterministic finite automata (NFA) for the regular expressions, combine these NFAs together with a new starting state, convert the resulting NFA to a DFA and minimize it .
Syntax Analyzer creates the syntactic structure of the given source program. The syntax of a programming is described by a context-free grammar (CFG). The syntax analyzer (parser) checks whether a given source program satisfies the rules implied by a context-free grammer or not
The parser generator expects an LL (1) grammar as input so it eliminating grammar left recursion and performing left factoring then computes First and Follow sets and uses them to construct a predictive parsing table for the grammer.