• Every C-Program statement contains C-token.
  • A token is a smallest unit in C-programing language.
  • They are the building blocks of the program.
  • C-token can be divided into the following categories.


[1] Keyword 
  • A keyword is a basic building block of any programming language.
  • Their meanings are per-defined to the compiler and it cannot be change.
  • C-language provides 32 keyword.
  • All c – keyword are written in lower case only.
  • It cannot be used as a variable name.
  • Example of some keyword are main, break, if ,int, float,for,exit,etc..
[2] Identifier:
  • An identifier is a named memory area that is used to store value.
  • It is user define name that are used to refer any variable array or function.
  • Identifier can be defining using both lower case and upper case letters but normally lower case letters are used.
  • Each identifier should follow naming convention rules.
  • Some valid identifier examples are: name, salary, year, amount, etc.
[3] Constant
  • A constant is a variable whose value does not change throughout the program.
  • It can be further divided into the following categories.
[1] Numeric Constant:
  • A numeric constant contain digits from 0 to 9.
  • It has the following two types:
[A] Integer Constant:
  • An integer constant contains integer value; it does not contain fractional part.
  • It may be negative or positive.
  • Example: 100, -25, 50
  • An integer constant may also represent in following three types.

         [a] Decimal                  [b] Octal                      [c] Hexadecimal

(B) Real Constant:
  • A real constant contains numerical value with fractional part.
  • It may be positive or negative.
  • Example: 10.5, -0.050, 25.075
[2]    Character Constant:        
  • Character constant contains alphabets from a to z.
  • It can be represent in following forms
[A] Single Character Constant
  • Single character constant includes single character or digit enclosed by signal quote.
  • Example: ‘a’, ‘10’, ‘-5’
[B] String Constant
  • A string constant contains multiple characters enclosed by double quote
  • Example:”hello”, “123”, “ABC”.
[4] String:
  • String is a sequential series of characters enclosed within double quote(“”).
  • Example:”HELLO”,”123”,”ABC”
[5] Special symbols:
  • Some special symbols are used to specify the operation or to direct the compiler to perform the task.
  • Special symbols includes &,!,(), [],{},*,^,<>
[6] Operator:
  • Operators are used to direct the compiler to perform some logical or arithmetic calculation.
  • Operators are uses with the operand.
  • It can be dividing into the following categories.