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+.. _arduino-if:
+
+if (conditional) and ==, !=, <, > (comparison operators)
+========================================================
+
+**``if``**, which is used in conjunction with a comparison
+operator, tests whether a certain condition has been reached, such
+as an input being above a certain number. The format for an if test
+is:
+
+
+
+::
+
+    if (someVariable > 50)
+    {
+      // do something here
+    }
+
+
+
+The program tests to see if someVariable is greater than 50. If it
+is, the program takes a particular action. Put another way, if the
+statement in parentheses is true, the statements inside the
+brackets are run. If not, the program skips over the code.
+
+
+
+The brackets may be omitted after an *if* statement. If this is
+done, the next line (defined by the semicolon) becomes the only
+conditional statement.
+
+::
+
+    
+    if (x > 120) digitalWrite(LEDpin, HIGH); 
+    
+    if (x > 120)
+    digitalWrite(LEDpin, HIGH); 
+    
+    if (x > 120){ digitalWrite(LEDpin, HIGH); } 
+    
+    if (x > 120){ 
+      digitalWrite(LEDpin1, HIGH);
+      digitalWrite(LEDpin2, HIGH); 
+    }                                 // all are correct
+
+
+
+The statements being evaluated inside the parentheses require the
+use of one or more operators:
+
+
+
+Comparison Operators:
+~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+     x == y (x is equal to y)
+     x != y (x is not equal to y)
+     x <  y (x is less than y)  
+     x >  y (x is greater than y) 
+     x <= y (x is less than or equal to y) 
+     x >= y (x is greater than or equal to y)
+
+
+
+Warning:
+--------
+
+Beware of accidentally using the single equal sign
+(e.g.``if (x = 10)`` ). The single equal sign is the assignment
+operator, and sets x to 10 (puts the value 10 into the variable x).
+Instead use the double equal sign (e.g.``if (x == 10)``), which is
+the comparison operator, and tests *whether* x is equal to 10 or
+not. The latter statement is only true if x equals 10, but the
+former statement will always be true.
+
+
+
+This is because C evaluates the statement ``if (x=10)`` as follows:
+10 is assigned to x (remember that the single equal sign is the
+`assignment operator <http://arduino.cc/en/Reference/Assignment>`_),
+so x now contains 10. Then the 'if' conditional evaluates 10, which
+always evaluates to TRUE, since any non-zero number evaluates to
+TRUE. Consequently, ``if (x = 10)`` will always evaluate to TRUE,
+which is not the desired result when using an 'if' statement.
+Additionally, the variable x will be set to 10, which is also not a
+desired action.
+
+
+
+**if** can also be part of a branching control structure using the
+`if...else <http://arduino.cc/en/Reference/Else>`_] construction.