Can a mobile application that is developed to work on Bluetooth technology be used on Bluetooth LE technology?

Can a mobile application that is developed to work on Bluetooth technology be used on Bluetooth LE technology?

Or does the developer need to modify code to handle Bluetooth LE (Smart) signals, input, output etc. ?

EDIT

While i was asking this question i want to know

if i write a code piece, can i run it on BLE devices, also with BLE performance?

Is it possible, or not?

If a device can have both B and BLE then i have one more question:

Should we write code with different APIs for ordinary B and BLE?

I don't know of any phone that is doing BTLE but not classic Bluetooth as well. So the application should still work but it will still just be using the classic Bluetooth portion of the hardware.

Of course from the sensor of other device your talking to point of view the situation may well be different as there are BTLE only sensors for example that may have a similar function to an old style Bluetooth sensor but they want be compatible. E.g. some classic Heart Rate sensors and modern BTLE heart rate sensors.