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Constructs an instance of the String class. There are multiple versions that construct Strings from different data types (i.e. format them as sequences of characters), including:

  • a constant string of characters, in double quotes (i.e. a char array)
  • a single constant character, in single quotes
  • another instance of the String object
  • a constant integer or long integer
  • a constant integer or long integer, using a specified base
  • an integer or long integer variable
  • an integer or long integer variable, using a specified base

Constructing a String from a number results in a string that contains the ASCII representation of that number. The default is base ten, so

String thisString = String(13)

gives you the String "13". You can use other bases, however. For example,

String thisString = String(13, HEX)

gives you the String "D", which is the hexadecimal representation of the decimal value 13. Or if you prefer binary,

String thisString = String(13, BIN)

gives you the String "1101", which is the binary representation of 13.


String(val, base)


val: a variable to format as a String - string, char, byte, int, long, unsigned int, unsigned long
base (optional) - the base in which to format an integral value


an instance of the String class


All of the following are valid declarations for Strings.

String stringOne = "Hello String";                     // using a constant String
String stringOne =  String('a');                       // converting a constant char into a String
String stringTwo =  String("This is a string");        // converting a constant string into a String object
String stringOne =  String(stringTwo + " with more");  // concatenating two strings
String stringOne =  String(13);                        // using a constant integer
String stringOne =  String(analogRead(0), DEC);        // using an int and a base
String stringOne =  String(45, HEX);                   // using an int and a base (hexadecimal)
String stringOne =  String(255, BIN);                  // using an int and a base (binary)
String stringOne =  String(millis(), DEC);             // using a long and a base

See also

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The text of the Arduino reference is licensed under a Creative Commons Attribution-ShareAlike 3.0 License. Code samples in the reference are released into the public domain.