C++ Tokens :

In a passage of text, individual words and punctuation marks are called tokens, lexical units or lexical elements. C++ has the following tokens :

• Keywords
• Identifiers
• Literals
• Punctuator
• Operators

Keywords :

Keywords are the words that convey a special meaning to the language compiler. These are reserved for special purpose and must not be used as normal identifier names.

1. asm
2. auto
3. break
4. case
5. catch
6. char
7. class
8. const
9. continue
10. default
11. delete
12. do
13. double
14. else
15. enum
16. extern
17. float
18. for
19. friend
20. goto
21. if
22. inline
23. int
24. long
25. new
26. operator
27. private
28. protected
29. public
30. register
31. return
32. short
33. signed
34. sizeof
35. static
36. struct
37. switch
38. temple
39. this
40. throw
41. try
42. typedef
43. union
44. unsigned
45. virtual
46. void
47. volatile
48. while

Identifiers :

Identifiers are fundamental building blocks of a program and are used as the general terminology for the names given to different parts of the program.
The following are some valid identifiers :

1. Myfile
2. MYFILE
3. _CHK
4. DATE_7_77
5. _DS
6. FILE13
7. Z2T0Z9
8. _HJI3_JK

The following are some invalid identifiers :

• DATA-REC (contains special character [ other than A-Z, a-z and _ ] )
• 29CLCT (Starting with a digit)
• break (reserved keywords)
• My.file (contains special character dot (.) )

Literals :

Literals are are data items that never change their value during a program run. C++ allows server kinds of literals :

• bool literal
• integer constant
• character constant
• floating constant
• string literal

bool literal

The bool literal in C++ is used to represent one of the two boolean values (true - boolean true or false - boolean false). Internally boolean true has value of 1 and boolean false has value of 0.

integer constant

Integer constants are whole numbers with out any fractional part. The method of writing integer constants has been specified in the following rule :

• Decimal Integer Constants - An integer constant consisting of a sequence of digits is taken to be decimal integer constant unless it begins with 0.
• Octal Integer Constants - A sequence of digits starting with 0 is taken to be an octal integer.
• Hexadecimal Integer Constants - A sequence of digits preceded by 0x or 0X is taken to be an hexadecimal integer.

character constant

A character constant is one character enclosed in single quotes, as in 'Z' ( Escape Sequences in C++ ) .

floating constant

Real constants are numbers having fractional parts. The following are valid real constants in fractional form :

2.0, 17.5, -15.0, -0.15255

The following are invalid real constants :

7 - No decimal point
7. - No digit after decimal point
+17/6 - '/' Illegal symbol
525.68.01 - Two decimal points
5258,01 - comma not allowed

string literal

'Multiple Character' constants are treated as string literal. A string literal is a sequence of characters surrounded by double quotes ( "abcd" ).

Punctuator :

The following characters are used as punctuator is C++:

Brackets [ ]

Opening and closing brackets indicate single and multidimensional array subscripts.

Parentheses ( )

Opening and closing parentheses indicate function calls and function parameters. Parentheses also group expressions and isolate conditional expressions.

Braces { }

Opening and closing braces indicate the start and end of compound statement (block of code containing more than one executable statements).

Comma ,

It is used as a separator in a function arguments lists.

Semicolon ;

It is used as a statement terminator. Every executable statement is terminated by a semicolon (;).

Colon :

It indicates a labeled statement.

Asterisk *

It is used for pointer declaration and the asterisk is also used as an operator to either pointer or as the multiplication operator.

Ellipsis ...

Ellipsis (...) are used in the formal argument lists of function prototypes to indicate a variable number of argument.

Equal to sing =

It is used for variable initial and as an assignment operator in expressions.

Pound sing #

The pound sign(#) is used for preprocessor directive and double pound sing(##) is also used as operators to perform token replacement and during the preprocessor scanning phase.

Operators :

Operators and Expressions - Operators are tokens that trigger some computation when applied to variables and other objects in an expression. The following list gives a brief description of the operators and their functions :

Unary operators :

Unary operator are those operators that require one operator to operate upon. following are some unary operators :

• & Address operator
• * Indirection operator
• + Unary plus
• - Unary minus
• ~ Bitwise complement
• ++ increment operator
• -- decrement operator
• & Address operator
• ! Logical negation

Binary operators :

Binary operators are those operators that require two operands to operate upon. following are some binary operators :

Arithmetic Operators
+	Addition
-	Subtraction
*	Multiplication
/	Division
%	Remainder / Modulus

Shift Operators
<<	shift left
>>	shift right

Bitwise Operators
&	Bitwise AND
^	Bitwise exclusive OR (XOR)
|	Bitwise OR

Logical Operators
&&	Logical AND
||	Logical OR

Assignment Operators
=	Assignment
/=	Assign quotient
+=	Assign sum
<<=	Assign left shift
&=	Assign bitwise AND
*=	Assign product
%=	Assign remainder
-=	Assign difference
>>=	Assign right shift
^=	Assign bitwise or (XOR)

Relational Operators
<	Less than
>	Greater than
<=	Less than or equal to
>=	Greater than or equal to
==	Equal to
!=	Not equal to

Component selection Operators
	Direct component selector
	Indirect components selector

Class member Operators
::	Scope access/resolution
.*	Deference pointer to class member
-->*	Deference pointer to class member

Conditional Operators
?	Ternary
:	Ternary

Escape Sequence in C++ :

Escape Sequence	Non-graphic Character
\a	Audible bell (alert)
\b	Backspace
\f	Formfeed
\n	Newline or linefeed
\r	Carriage Return
\t	Horizontal tab
\v	Vertical tab
\\	Backslash
\'	Single quote
\"	Double quote
\?	Question mark
\On	Octal number
\xHn	Hexadecimal number
\0	Null