do while

Description

The do...while loop will execute the code block first, and then checking if the condition is true, then it will repeat the loop as long as the condition is true.

The do...while loop works in the same manner as the while loop, with the exception that the condition is tested at the end of the loop, so the do loop will always run at least once.

Syntax

do { // block of code } while (condition);

Parameter Values

  • condition: a boolean expression that evaluates to true or false.

Example Code

Example Code 1

void setup() { Serial.begin(9600); Serial.println("====== TEST START ======"); int i = 0; do { Serial.print("Inside the DO WHILE loop: i = "); Serial.println(i); i++; // increase i by 1 } while (i < 5); Serial.println("====== TEST END ========"); } void loop() { }

The result on Serial Monitor:

COM6
Send
====== TEST START ====== Inside the DO WHILE loop: i = 0 Inside the DO WHILE loop: i = 1 Inside the DO WHILE loop: i = 2 Inside the DO WHILE loop: i = 3 Inside the DO WHILE loop: i = 4 ====== TEST END ========
Autoscroll Show timestamp
Clear output
9600 baud  
Newline  

Example Code 2

int x = 0; do { delay(50); // wait for sensors to stabilize x = readSensors(); // check the sensors } while (x < 100);

do...while loop vs while loop

The while loop checks the condition before executing the block of code; conversely, the do while loop checks the condition after executing the block of code. Therefore, the do while loop will always be executed at least once, even if the condition is false at the beginning.

The do...while and while loop are the same, except for the case in which the condition is false at the beginning.

For example:

  • Code with do...while loop
void setup() { Serial.begin(9600); Serial.println("====== TEST START ======"); int i = 10; do { Serial.print("Inside the DO WHILE loop: i = "); Serial.println(i); i++; // increase i by 1 } while (i < 5); Serial.println("====== TEST END ========"); } void loop() { }
COM6
Send
====== TEST START ====== Inside the DO WHILE loop: i = 10 ====== TEST END ========
Autoscroll Show timestamp
Clear output
9600 baud  
Newline  
  • Code with while loop
void setup() { Serial.begin(9600); Serial.println("====== TEST START ======"); int i = 10; while (i < 5) { Serial.print("Inside the DO WHILE loop: i = "); Serial.println(i); i++; // increase i by 1 } Serial.println("====== TEST END ========"); } void loop() { }
COM6
Send
====== TEST START ====== ====== TEST END ========
Autoscroll Show timestamp
Clear output
9600 baud  
Newline  

※ NOTES AND WARNINGS:

There are three ways to escape the do while loop:

  • The condition of the do while loop becomes false.
  • The execution of the code reaches a break statement inside the loop.
  • The execution of the code reaches a goto statement inside the loop, which jumps to a label located outside of the loop.

See Also

ARDUINO BUY RECOMMENDATION

Arduino UNO R3
Arduino Starter Kit
Please note: These are Amazon affiliate links. If you buy the components through these links, We will get a commission at no extra cost to you. We appreciate it.

※ OUR MESSAGES