Final answer:
A scanner, or lexer, in a compiler or interpreter reads source code to produce tokens, which are the basic syntactic elements. A parser then analyzes these tokens to determine the code's grammatical structure, producing a parsing tree that represents the program's logic for subsequent compilation stages.
Step-by-step explanation:
What is a Scanner and a Parser in an Interpreter or Compiler?
In the context of an interpreter or compiler, a scanner (also known as a lexer) is responsible for reading the source code and converting it into meaningful tokens. Tokens are the basic building blocks of code, such as keywords, operators, identifiers, and literals. The scanner disregards whitespace, comments, and other irrelevant characters, focusing only on important syntactic elements.
After the scanning phase, a parser takes over. The parser analyzes the sequence of tokens produced by the scanner to determine the grammatical structure. This involves checking the code against the rules of the programming language's grammar, typically represented in the form of a parsing tree. The parser must ensure that the code is structurally sound and may fill in details to create a more complete representation of the program's meaning which is used in subsequent stages of compilation.
The role of the scanner is to break down the code into manageable pieces, while the parser's job is to interpret these pieces and build a structure that represents the program's logic and flow. Both are crucial steps in the process of translating human-readable code into machine code or intermediate representations in interpreting or compiling languages.