# Lesson 6: Conditional, Equality and Relational Operators

### The “if” statement

The “if” statement allows us to execute a statement or a block of code, if a certain condition is TRUE.

Syntax:

#### Single Statement

`if ( condition ) statement;`
`if ( x > 10 ) Serial.println(x);`

#### Block of code between { }

`if ( condition ) {    statement;    statement;    statement; }`
`if ( x > 10 ) {    Serial.print(“x = “);    Serial.println(x); }`

### The “if-else” statements

The “if-else” statement allows us to execute a statement or block of code if a condition is TRUE, but if the condition is FALSE, it allows us to execute a different statement of block of code.

Allows us to select between two or more alternatives.

Syntax:

##### Single Statement
`if ( condition )   statement; else   statement;`
`if ( x > 10 )   Serial.print(“x is > 10”); else   Serial.print(“x is not > 10”);`

Block of code between { }

`if ( condition ) {    statement;    statement;    statement; }`
`if ( x > 10 ) {    Serial.print(“x = “);    Serial.println(x); } else {    Serial.print(“x is not > 10. ”);    Serial.println(“x = “ + x); }`

### The “if-else-if” statements

Syntax:

`if ( condition )   statement; else if ( condition )   statement; else   statement;`
`if ( x > 10 )   Serial.println(“x is > 10”); else if ( x > 20 )   Serial.println(“x is > 20”); else   Serial.println(“x is not > 10 or 20”)`
`if ( condition ) {    statement;    statement; } else if {    statement;    statement; } else {    statement;    statement; }`
`if ( x > 10 ) {   Serial.print(“x = “);   Serial.println(x); } else if ( x > 20) {   Serial.print(“x is not > 10. ”);   Serial.print(“x = “);   Serial.println(x); } else {   Serial.print(“x = “;   Serial.println(x); }`

### Equality and Relational Operators

The equality and relational operators determine if one operand is equal to, greater than, less than or not equal to another operand.

`==`

Equal to

Keep in mind that you use “==” to test equality not “=”

`!=`

Not equal to

`>`

Greater than

`>=`

Greater than or equal to

`<`

Less than

`<=`

Less than or equal to

### Conditional Operators

`&&`

AND

The “&” symbol is called ampersand

e.g.

// …
}

`||`

OR

The “|” symbol is called the pipe symbol. It is the symbol located above the Enter key on a US QWERTY keyboard.

e.g.

if (x > 0 || y > 0) {
// …
}

`!`

NOT

TRUE if the operand is false

e.g.

if (!x) {
// …
}