C Programming/Tokens: Difference between revisions
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(Created page with "== C Tokens == C Supports Six Types of Tokens: # Identifiers # Keywords # Constants # Strings # Op...") |
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# [[C_Programming/C_Tokens#Identifiers |Identifiers ]] | # [[C_Programming/C_Tokens#Identifiers |Identifiers ]] | ||
# [[C_Programming/C_Tokens#Keywords|Keywords]] | # [[C_Programming/C_Tokens#Keywords|Keywords]] | ||
# Constants | # [[C_Programming/C_Tokens#Constants |Constants ]] | ||
# Strings | # Strings | ||
# Operators | # Operators | ||
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| do || if || static || while | | do || if || static || while | ||
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=== Constant === | |||
A constant is an identifier whose value cannot be altered in a program. For example: 1, 2.5, "C programming is easy", etc. | |||
== Differentiate == | == Differentiate == | ||
Revision as of 02:48, 5 February 2018
C Tokens
C Supports Six Types of Tokens:
- Identifiers
- Keywords
- Constants
- Strings
- Operators
- Special Symbols
Identifiers
Identifiers are names for entities in a C program, such as variables, arrays, functions, structures, unions and labels. An identifier can be composed only of uppercase, lowercase letters, underscore and digits, but should start only with an alphabet or an underscore.
Rules for Naming Identifiers:
- An identifier can only have alphanumeric characters (a-z , A-Z , 0-9) (i.e. letters & digits) and underscore( _ ) symbol.
- Identifier names must be unique
- The first character must be an alphabet or underscore.
- Cannot be keyword as identifiers.
- Should not be of length more than 31 characters.
- Must not contain white spaces.
- Identifiers are case-sensitive.
Kinds of identifiers:
- Internal
- External
Keywords
| auto | double | int | struct |
| break | else | long | switch |
| case | enum | register | typedef |
| char | extern | return | union |
| const | float | short | unsigned |
| continue | for | signed | void |
| default | goto | sizeof | volatile |
| do | if | static | while |
Constant
A constant is an identifier whose value cannot be altered in a program. For example: 1, 2.5, "C programming is easy", etc.
Differentiate
Keywords vs Identifiers
| Keyword | Identifier |
|---|---|
| Predefined-word | User-defined word |
| Must be written in lowercase only | Can written in lowercase and uppercase |
| Has fixed meaning | Must be meaningful in the program |
| Whose meaning has already been explained to the C compiler | Whose meaning not explained to the C compiler |
| Combination of alphabetic characters | Combination of alphanumeric characters |
| Used only for it intended purpose | Used for required purpose |
| Underscore character is not considered as a letter | Underscore character is considered as a letter |