Parser

Parser

• A parser is a compiler or interpreter component that breaks data into smaller elements for easy translation into another language. 
• A parser takes input in the form of a sequence of tokens or program instructions and usually builds a data structure in the form of a parse tree or an abstract syntax tree.

Working

The overall process of parsing involves three stages:

1. Lexical Analysis: It produces tokens from a stream of input string characters, which are broken into small components to form meaningful expressions.

2. Syntactic Analysis: Checks whether the generated tokens form a meaningful expression. This makes use of a context-free grammar that defines algorithmic procedures for components. These work to form an expression and define the particular order in which tokens must be placed.

3. Semantic Parsing: The final parsing stage in which the meaning and implications of the validated expression are determined and necessary actions are taken.

Parsers are widely used in the following technologies:

• Java and other programming languages

• HTML and XML

• Interactive data language and object definition language

• Database languages, such as SQL

• Modeling languages, such as virtual reality modeling language

• Scripting languages

• Protocols, such as HTTP and Internet remote function calls

Compiler

• A compiler is a special program that processes statements written in a particular programming language and turns them into machine language.  
• Typically, a programmer writes language statements in a language one line at a time using an editor . 
• The file that is created contains what are called the source statements . 
• When executing (running), the compiler first parses (or analyzes) all of the language statements syntactically one after the other.
• The Java programming language, a language used in object-oriented programming, has introduced the possibility of compiling output (called bytecode ) that can run on any computer system platform. 
• The Java virtual machine or bytecode interpreter is provided to convert the bytecode into instructions that can be executed by the actual hardware processor. 
• Using this virtual machine, the bytecode can optionally be recompiled at the execution platform by a just-in-time compiler .