Difference Between Tokens and Terminals
Last Updated :
29 Jul, 2024
In computer science and programming languages syntax analysis, and parsing tokens and terminals are considered as the basic unit. They are the basic meaningful divisions of input data that are isolated by the lexical analyzer during the first stage of a compiler’s functioning. These tokens are then used in the formation of terminals which are the smaller alphabet building blocks of the language.
It is important to learn about tokens and terminals for anyone exploring compilers and interpreters since these entities are vital in the conversion of source code from human format to machine format. Through understanding these concepts, learners are in a position to understand the involved intricacies in language translation and code execution.
What are Tokens?
Tokens are alphanumeric characters. It is the smallest unit of grammar in programming languages. When we give input to the lexical analyzer it reads the characters and converts them to tokens which later proceed through further phases of compilation. Tokens are categorized into various types: Keywords, Operators, Strings, Constants, Special Characters, and Identifiers. Example: A, @, b, (, ), etc.
What are Terminals?
The terminal is a symbol that appears on the right side of the production rule and cannot be changed using the grammar rules. Terminal symbols are a set of tokens and are characters from which strings are produced. They are represented by using lowercase letters. Examples a, b, c, etc.
Difference Between Tokens and Terminals
S.No | Tokens | Terminals |
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1. | Tokens are a set of strings used in a programming language. | Terminals are a set of characters used in production rules. |
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2. | The compiler breaks a program into the smallest units known as tokens which are passed through various stages of the compiler. | Symbols or tokens are called terminals when they are used in formal languages. |
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3. | Tokens can be written in upper case letters. | Terminals are written only in lower case letters. |
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4. | It can have letters, numbers, and special characters. | It has only alphabets. |
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5. | They are generated by a lexical analyzer. | They are defined by formal languages. |
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6. | Tokens are used to describe the corresponding characters in the source. | Terminals are used to describe the working of the parser that is with which it is working. |
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7. | Examples are A, @, b, (, ), etc | Examples are a, b, c, d, etc. |
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Conclusion
In conclusion, tokens and terminals are significant but different entities in the compilation and semantics of programming languages. These are produced by the lexical analyzer and are the smallest components of the language, for example, keywords, operators and identifiers among others. Terms are the marks of the language’s grammar with which syntactic structures are built, on the other hand, terminals are the marks. This clear separation is crucial for comprehending lexical analysis and syntax parsing since tokens make it easier to analyze and differentiate between terminals to produce a proper translation from the source code to an executable program.