C Tokens, Keywords, Identifiers 

What is a Character set?

Like every other language, 'C' also has its own character set. A program is a set of instructions that, when executed, generate an output. The data that is processed by a program consists of various characters and symbols. The output generated is also a combination of characters and symbols.

A character set in 'C' is divided into,

• Letters
• Numbers
• Special characters
• White spaces (blank spaces)

A compiler always ignores the use of characters, but it is widely used for formatting the data. Following is the character set in 'C' programming:

1. Letters
• Uppercase characters (A-Z)
• Lowercase characters (a-z)
2. Numbers
• All the digits from 0 to 9
3. White spaces
• Blank space
• New line
• Carriage return
• Horizontal tab
4. Special characters
• Special characters in 'C' are shown in the given table,
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• What is Token in C?

  TOKEN is the smallest unit in a 'C' program. It is each and every word and punctuation that you come across in your C program. The compiler breaks a program into the smallest possible units (tokens) and proceeds to the various stages of the compilation. A token is divided into six different types, viz, Keywords, Operators, Strings, Constants, Special Characters, and Identifiers.

   

  Tokens in C

  

  
   

  Keywords and Identifiers

  In 'C' every word can be either a keyword or an identifier.

  Keywords have fixed meanings, and the meaning cannot be changed. They act as a building block of a 'C' program. There are a total of 32 keywords in 'C'. Keywords are written in lowercase letters.

  Following table represents the keywords in 'C'-  
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An identifier is nothing but a name assigned to an element in a program. Example, name of a variable, function, etc. Identifiers are the user-defined names consisting of 'C' standard character set. As the name says, identifiers are used to identify a particular element in a program. Each identifier must have a unique name. Following rules must be followed for identifiers:

1. The first character must always be an alphabet or an underscore.
2. It should be formed using only letters, numbers, or underscore.
3. A keyword cannot be used as an identifier.
4. It should not contain any whitespace character.
5. The name must be meaningful.

Summary

• A token is the smallest unit in a program.
• A keyword is reserved words by language.
• There are total of 32 keywords.
• An identifier is used to identify elements of a program.