The component of an IoT system that executes a program is the microcontroller (MCU). The microcontroller acts as the brain of the IoT device, containing a control unit, memory (such as flash memory), timers, and converters, which together enable it to run and control the program that manages the device's functions

. It processes data from sensors, controls actuators, and manages communication with other devices or the cloud. Examples of popular MCUs used in IoT systems include the ESP32 and ESP8266, which integrate processing power with communication capabilities like Wi-Fi and Bluetooth

. In summary, the microcontroller is the central processing component responsible for executing the software program in an IoT system.