Elena has written a Python program to manage a smart heating system.
Read the following code:
def adjust_temperature(target_temp):
current_temp = read_sensor()
if current_temp < target_temp:
turn_heater_on()
else:
turn_heater_off()
# Main program
user_setting = 21
adjust_temperature(user_setting)
Identify the name of the variable passed from the main program to the subprogram.