OR

• Boolean operators

These operators can be used in if conditional statement.

• &&（Logical and）

Only both the two operands are true is it be true. For example：

```
if (digitalRead(2) == HIGH  && digitalRead(3) == HIGH) { // read the levels of the two switch
// ...
}
```

When both input levels are high levels, it is true.

• ||（Logical or）

If only one operand is true, it is true. For example：

```
if (x > 0 || y > 0) {
// ...
}
```

If x or y is larger than 0, it is true

• ！（Logical negation）

If operand is false, it is true For example

```
if (!x) {
// ...
}
```

If x is false, it is true（namely, x is equal to 0）.

• For example
```
if (a >= 10 && a <= 20){}   // if the value of a is between 10 and 20, it is true
```
• Note

You mustn't take the bitwise operator “and” whose sign is &(single) as same to boolean operator“and” whose sign is &&（double）, which are completely different operators.

In the same way, don’t mix boolean operator || and bitwise operator “or”| up .

Bitwise operator 〜（tilde）looks like very different from boolean operator not！（just as the programmer say ：“bang”）. But you still should to confirm which operator you want.