The is a fundamental tool for Arduino users whoWhile most Arduino boards come with at least one hardware serial port (UART), you often need additional ports to talk to peripherals like GPS modules, Bluetooth adapters, or GSM shields. How to Download and Install SoftwareSerial
In almost all modern cases, you SoftwareSerial separately. software serial library download arduino
Where to download SoftwareSerial - Libraries - Arduino Forum The is a fundamental tool for Arduino users