======compound bitwise OR (|=)   ======

====Description    ====

The compound bitwise OR operator (|=) is often used with a variable and a constant to "set" (set to 1) particular bits in a variable.

====Syntax:   ====
<code arduino>
x |= y;   // equivalent to x = x | y; </code>

====Parameters   ====

x: a char, int or long variable\\
y: an integer constant or char, int, or long


====Example:   ====

First, a review of the Bitwise OR (|) operator
<code arduino>
   0  0  1  1    operand1
   0  1  0  1    operand2
   ----------
   0  1  1  1    (operand1 | operand2) - returned result
</code>
Bits that are "bitwise ORed" with 0 are unchanged, so if myByte is a byte variable,\\

myByte | B00000000 = myByte;

Bits that are "bitwise ORed" with 1 are set to 1 so:\\
myByte | B11111111 = B11111111;

Consequently - to set bits 0 & 1 of a variable, while leaving the rest of the variable unchanged, use the compound  bitwise OR operator (|=) with the constant B00000011
<code arduino>
   1  0  1  0  1  0  1  0    variable
   0  0  0  0  0  0  1  1    mask
   ----------------------
   1  0  1  0  1  0  1  1
   
 variable unchanged
                     bits set
   
</code>
Here is the same representation with the variables bits replaced with the symbol x

<code arduino>
   x  x  x  x  x  x  x  x    variable
   0  0  0  0  0  0  1  1    mask
   ----------------------
   x  x  x  x  x  x  1  1
  
 variable unchanged
                     bits set
</code>
So if:
<code arduino>
myByte =  B10101010;

myByte |= B00000011 == B10101011;
</code>

See Also
* [[arduino:bitwise operators:BitwiseCompoundAnd | &=]] (compound bitwise and)
* [[arduino:bitwise operators:BitwiseAnd | &]] (bitwise and)
* [[arduino:bitwise operators:BitwiseAnd | |]] (bitwise or)

Source: arduino.cc