How to multiply strings?
You can write a helper function to do it, like this:

void printRepeat (Stream &amp; device, const char * str, unsigned int count)
  {
  while (count-- &gt; 0)
    device.print (str);
  }   // end of printRepeat

void setup() 
  {
  Serial.begin (115200);
  printRepeat (Serial, "-", 20);
  Serial.println ();
  } // end of setup

void loop() 
{
  printRepeat (Serial, "Hello, World! ", 5);
  Serial.println ();
  delay (500);
} // end of loop


The function printRepeat is passed a Stream argument, which can be something like Serial, Serial1, a SoftwareSerial instance, and so on.