If Statement (Conditional Statement)

The if() statement is the most basic of all programming control structures. It allows you to make something happen or not, depending on whether a given condition is true or not. It looks like this:

if (someCondition) {   // do stuff if the condition is true}

There is a common variation called if-else that looks like this:

if (someCondition) {   // do stuff if the condition is true} else {   // do stuff if the condition is false}

There's also the else-if, where you can check a second condition if the first is false:

if (someCondition) {   // do stuff if the condition is true} else if (anotherCondition) {   // do stuff only if the first condition is false   // and the second condition is true}

You'll use if statements all the time. The example below turns on an LED on pin 13 (the built-in LED on many Arduino boards) if the value read on an analog input goes above a certain threshold.

Hardware Required

Circuit

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image developed using Fritzing. For more circuit examples, see the Fritzing project page

Schematic

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Code

In the code below, a variable called analogValue is used to store the data collected from a potentiometer connected to the board on analogPin 0. This data is then compared to a threshold value. If the analog value is found to be above the set threshold the built-in LED connected to digital pin 13 is turned on. If analogValue is found to be < (less than) threshold, the LED remains off.

See Also

• if()
• if...else
• analogRead()
• digitalWrite()
• serial.begin()
• serial.print()

• Arrays - A variation on the For Loop example that demonstrates how to use an array.
• ForLoopIteration - Control multiple LEDs with a for loop.
• switchCase - How to choose between a discrete number of values.
• switchCase2 - A second switch-case example, showing how to take different actions based on the characters received in the serial port.
• WhileStatementConditional - How to use a while loop to calibrate a sensor while a button is being read.

Last revision 2015/07/29 by SM