String Character Functions

The String functions charAt() and setCharAt() are used to get or set the value of a character at a given position in a String.

At their simplest, these functions help you search and replace a given character. For example, the following replaces the colon in a given String with an equals sign:

 String reportString = "SensorReading: 456";
 int colonPosition = reportString.indexOf(':');
 reportString.setCharAt(colonPosition, '='); 

Here's an example that checks to see if the first letter of the second word is 'B':

 String reportString = "Franklin, Benjamin";
 int spacePosition = reportString.indexOf(' ');
 if (reportString.charAt(spacePosition + 1) == 'B') {
    Serial.println("You might have found the Benjamins.")
 }

Caution: If you try to get the charAt or try to setCharAt() a value that's longer than the String's length, you'll get unexpected results. If you're not sure, check to see that the position you want to set or get is less than the string's length using the length() function.

Step 1: What You Need?

1 x Arduino Board ( Arduino UNO R3 used in this tutorial.)
1 x USB Type-B Cable 


Optional 

Arduino Uno R3 Acrylic Transparent Casing

Arduino Compatible UNO Ultimate Starter Kit / Learning Kit

Don't have components? Don't worry. Just click the component's name. 

Step 2: Build Your Circuit.

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.

Step 3: Upload The Code.

1. Select the Arduino board type: Select Tools >> Board >> Select your correct Arduino board used.

2. Find the port number by accessing device manager on Windows. See the section Port (COM&LPT) and look for an open port named "Arduino Uno (COMxx)". If you are using a different board, you will find a name accordingly. What matters is the xx in COMxx part. In my case, it's COM3. So my port number is 3.

Select the right port: Tools >> Port >> Select the port number.

3. You can find this code in the example of Arduino IDE.

Select File >> Examples >> 08. Strings >> StringCharacters

Click press the "upload" button (see the button with right arrow mark).

Download:

Arduino IDE

Sources:https://www.arduino.cc/en/Tutorial/StringCharacters

08.Strings library StringCharacters