String Case Change Functions

The String case change functions allow you to change the case of a String. They work just as their names imply. toUpperCase() changes the whole string to upper case characters, and toLowerCase() changes the whole String to lower case characters. Only the characters A to Z or a to z are affected.

Hardware Required

  • Arduino or Genuino Board


There is no circuit for this example, though your board must be connected to your computer via USB and the serial monitor window of the Arduino Software (IDE) should be open.

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


  String Case changes

  Examples of how to change the case of a String

  created 27 Jul 2010
  modified 2 Apr 2012
  by Tom Igoe

  This example code is in the public domain.

void setup() {
  // Open serial communications and wait for port to open:
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only

  // send an intro:
  Serial.println("\n\nString case changes:");

void loop() {
  // toUpperCase() changes all letters to upper case:
  String stringOne = "<html><head><body>";

  // toLowerCase() changes all letters to lower case:
  String stringTwo = "</BODY></HTML>";

  // do nothing while true:
  while (true);

See Also

Last revision 2015/08/11 by SM