do - while

The do 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.

do
{
    // statement block
} while (test condition);

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

Source: arduino.cc