

5
to the variable x
. The assignment operation always takes place from right to left, and never the other way around:


x
the value contained in variable y
. The value of x
at the moment this statement is executed is lost and replaced by the value of y
.y
to x
at the moment of the assignment operation. Therefore, if y
changes at a later moment, it will not affect the new value taken by x
.


a:4 b:7 
a
and b
(4 and 7, respectively). Notice how a
was not affected by the final modification of b
, even though we declared a = b
earlier.


y
is assigned the result of adding 2 and the value of another assignment expression (which has itself a value of 5). It is roughly equivalent to:


y
.


x
, y
and z
; always from righttoleft.operator  description 

+  addition 
  subtraction 
*  multiplication 
/  division 
%  modulo 
%
), gives the remainder of a division of two values. For example:


x
containing the value 2, since dividing 11 by 3 results in 3, with a remainder of 2.expression  equivalent to... 

y += x;  y = y + x; 
x = 5;  x = x  5; 
x /= y;  x = x / y; 
price *= units + 1;  price = price * (units+1); 


5 
++
) and the decrease operator (
) increase or reduce by one the value stored in a variable. They are equivalent to +=1
and to =1
, respectively. Thus:


x
.++x
) or after it (x++
). Although in simple expressions like x++
or ++x
, both have exactly the same meaning; in other expressions in which the result of the increment or decrement operation is evaluated, they may have an important difference in their meaning: In the case that the increase operator is used as a prefix (++x
) the value, the expression evaluates to the final value of x
, once it is already increased. On the other hand, in case that it is used as a suffix (x++
) the value stored in x
the expression evaluates to the value x
had before being increased. Notice the difference:Example 1  Example 2 

x = 3; 
x = 3; 
y
is the value of x
after being increased. While in Example 2, it is the value x
had before being increased.operator  description 

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


a=2
, b=3
and c=6
, then:


=
, with one equal sign) is not the same as the equality comparison operator (operator ==
, with two equal signs); the first one (=
) assigns the value on the righthand to the variable on its left, while the other (==
) compares whether the values on both sides of the operator are equal. Therefore, in the last expression ((b=2) == a
), we first assigned the value 2
to b
and then we compared it to a
(that also stores the value 2), yielding true
.!
is the C++ operator for the Boolean operation NOT. It has only one operand, to its right, and inverts it, producing false
if its operand is true
, and true
if its operand is false
. Basically, it returns the opposite Boolean value of evaluating its operand. For example:


&&
and 
are used when evaluating two expressions to obtain a single relational result. The operator &&
corresponds to the Boolean logical operation AND, which yields true
if both its operands are true
, and false
otherwise. The following panel shows the result of operator &&
evaluating the expression a&&b
:&& OPERATOR (and)  

a  b  a && b 
true  true  true 
true  false  false 
false  true  false 
false  false  false 

corresponds to the Boolean logical operation OR, which yields true
if either of its operands is true
, thus being false only when both operands are false. Here are the possible results of ab
: OPERATOR (or)  

a  b  a  b 
true  true  true 
true  false  true 
false  true  true 
false  false  false 


(5==5)(3>6)
), C++ evaluates first whether 5==5
is true
, and if so, it never checks whether 3>6
is true
or not. This is known as shortcircuit evaluation, and works like this for these operators:operator  shortcircuit 

&&  if the lefthand side expression is false , the combined result is false (the righthand side expression is never evaluated). 
  if the lefthand side expression is true , the combined result is true (the righthand side expression is never evaluated). 


i
by one, but only if the condition on the left of &&
is true
, because otherwise, the condition on the righthand side (++i<n
) is never evaluated.true
, and a different one if the expression evaluates as false
. Its syntax is:condition ? result1 : result2
condition
is true
, the entire expression evaluates to result1
, and otherwise to result2
.




7 
a
was 2, and b
was 7, so the expression being evaluated (a>b
) was not true
, thus the first value specified after the question mark was discarded in favor of the second value (the one after the colon) which was b
(with a value of 7).,
) is used to separate two or more expressions that are included where only one expression is expected. When the set of expressions has to be evaluated for a value, only the rightmost expression is considered.


b
, and then assign b+2
to variable a
. So, at the end, variable a
would contain the value 5 while variable b
would contain value 3.operator  asm equivalent  description 

&  AND  Bitwise AND 
  OR  Bitwise inclusive OR 
^  XOR  Bitwise exclusive OR 
~  NOT  Unary complement (bit inversion) 
<<  SHL  Shift bits left 
>>  SHR  Shift bits right 


3.14
to an integer value (3
); the remainder is lost. Here, the typecasting operator was (int)
. Another way to do the same thing in C++ is to use the functional notation preceding the expression to be converted by the type and enclosing the expression between parentheses:




x
is assigned the value 1
, because char
is a type with a size of one byte.sizeof
is a compiletime constant, so it is always determined before program execution.


x
, because the %
operator has a higher precedence than the +
operator, and is always evaluated before. Parts of the expressions can be enclosed in parenthesis to override this precedence order, or to make explicitly clear the intended effect. Notice the difference:


Level  Precedence group  Operator  Description  Grouping 

1  Scope  ::  scope qualifier  Lefttoright 
2  Postfix (unary)  ++   postfix increment / decrement  Lefttoright 
()  functional forms  
[]  subscript  
. >  member access  
3  Prefix (unary)  ++   prefix increment / decrement  Righttoleft 
~ !  bitwise NOT / logical NOT  
+   unary prefix  
& *  reference / dereference  
new delete  allocation / deallocation  
sizeof  parameter pack  
(type)  Cstyle typecasting  
4  Pointertomember  .* >*  access pointer  Lefttoright 
5  Arithmetic: scaling  * / %  multiply, divide, modulo  Lefttoright 
6  Arithmetic: addition  +   addition, subtraction  Lefttoright 
7  Bitwise shift  << >>  shift left, shift right  Lefttoright 
8  Relational  < > <= >=  comparison operators  Lefttoright 
9  Equality  == !=  equality / inequality  Lefttoright 
10  And  &  bitwise AND  Lefttoright 
11  Exclusive or  ^  bitwise XOR  Lefttoright 
12  Inclusive or    bitwise OR  Lefttoright 
13  Conjunction  &&  logical AND  Lefttoright 
14  Disjunction    logical OR  Lefttoright 
15  Assignmentlevel expressions  = *= /= %= += =  assignment / compound assignment  Righttoleft 
?:  conditional operator  
16  Sequencing  ,  comma separator  Lefttoright 
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