Explain the process of tokenization

Tokenization is the process of breaking down a sequence of text into meaningful units called tokens. This is a critical step in lexical analysis, particularly in compilers and text processing applications. Here’s a concise explanation of the process:

1. Input Text

• Starting Point: The process begins with a continuous sequence of text or code, such as a line of source code or a document.

2. Lexical Analysis

• Scanning: The lexer (or tokenizer) scans the input text from left to right, identifying segments that match predefined patterns.

3. Pattern Matching

• Regular Expressions: The lexer uses regular expressions or pattern rules to recognize different types of tokens (e.g., keywords, identifiers, literals, operators).
• Matching: As the lexer encounters text, it matches substrings against these patterns to determine the type of token.

4. Token Creation

• Classification: Each matched segment (lexeme) is classified into a specific token type (e.g., IDENTIFIER, NUMBER, OPERATOR).
• Tokenization: The matched lexemes are then converted into tokens, which are typically represented as pairs of token type and value (e.g., (NUMBER, 123)).

5. Token Output

• Token Stream: The lexer outputs a sequence of tokens, which can then be processed further by subsequent stages (e.g., parsing, semantic analysis).