C Tokens, Identifiers, Keywords: What is Tokens & Its Types
Benjamin Walker
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,
| Special Character | Description |
|---|---|
| , (comma) | { (opening curly bracket) |
| . (period) | } (closing curly bracket) |
| ; (semi-colon) | [ (left bracket) |
| : (colon) | ] (right bracket) |
| ? (question mark) | ( (opening left parenthesis) |
| ‘ (apostrophe) | ) (closing right parenthesis) |
| ” (double quotation mark) | & (ampersand) |
| ! (exclamation mark) | ^ (caret) |
| |(vertical bar) | + (addition) |
| / (forward slash) | – (subtraction) |
| \ (backward slash) | * (multiplication) |
| ~ (tilde) | / (division) |
| _ (underscore) | > (greater than or closing angle bracket) |
| $ (dollar sign) | < (less than or opening angle bracket) |
| % (percentage sign) | # (hash sign) |
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. C Token is divided into six different types, viz, Keywords, Operators, Strings, Constants, Special Characters, and Identifiers.
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’-
| Keywords in C Programming Language | |||
|---|---|---|---|
| auto | double | int | struct |
| break | else | long | switch |
| case | enum | register | typedef |
| char | extern | return | union |
| const | short | float | unsigned |
| continue | for | signed | void |
| default | goto | sizeof | volatile |
| do | if | static | while |
An identifier is nothing but a name assigned to an element in a program. Example, name of a variable, function, etc. Identifiers in C language 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:
- The first character must always be an alphabet or an underscore.
- It should be formed using only letters, numbers, or underscore.
- A keyword cannot be used as an identifier.
- It should not contain any whitespace character.
- The name must be meaningful.
Summary
- C Tokens in C language are the smallest units 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.
