String.charAt() Arduino Function

The string can save data that is of large size. While working with Arduino, strings are an important data type because they can store readings from different sensors. The String class in Arduino provides various functions to manipulate strings. One such function is String.charAt(). This article discusses String.charAt() function in detail.

What is String.charAt() in Arduino

The String.charAt() function in Arduino returns the character at a specific index position of a string. This function contains one parameter which is the index position of the character that we want to get from a string.


The syntax of String.charAt() function is:


In the above syntax, index keyword represents the position of a character in a string.

Return Type

This function gives us the character inside a string at the index number which we passed as a function parameter.


This function contains one parameter:

index – The index position of the character we want to know. It should be a positive integer representing the position of the character in the string.

How to Use String.charAt() in Arduino

To use the String.charAt() function in Arduino, follow these steps:

  • Create a string using the String class.
  • Call the charAt() function on this string object.
  • Pass the index position of the character that we want to know as a parameter to the charAt() function.

Below is the code that explains the usage of String.charAt() function in Arduino programming:

void setup() {


  String myString = "Linuxhint";

  char myChar = myString.charAt(4);

Serial.print("Character at index 4 is: ");



void loop() {


Code started by initializing serial communication in setup() function. After that, a new string variable myString with the value “Linuxhint” is defined.

The charAt() function is called on myString with an argument of 4. This will give us the characters at the 4th position inside a string. The counting for the index starts from the left and begins with the number 0. Once the character is read it will be stored in the myChar variable. In the last part of the code value of myChar is printed on the serial monitor.

The following output will appear as the fifth character of the string “Linuxhint” is “x”, so it will be printed to the serial monitor.

Note: String.charAt() function works with ASCII characters only. It cannot handle extended ASCII or Unicode characters.


The String.charAt() function in Arduino can give us the character at a specific position inside a string. Using this function, we can retrieve any character from a string by just passing the index number of the character as a parameter of this function. For details on syntax, parameters, and return value of this function read the article.

About the author


I am an Electrical Engineer. I love to write about electronics. I am passionate about writing and sharing new ideas related to emerging technologies in the field of electronics.