This Project is used to indicate the temperature and it is also used as controller. The system will get the temperature from the IC and it will display the temperature over the seven segment display/LCD display and this temperature was compared with the value stored by the user and if the Room temperature goes beyond the Preset temperature then an alarm is switched ON until the stop switch is pressed.The System is fully controlled by the microcontroller AT89S52. It is a popular 8 bit microcontroller. The circuit consists of four switches, in which two buttons are used to increment and decrement the temperature value and the next button is to start the Thermostat function and the other button is used to stop the thermostat function.