The domain of the function f(x) is the entire real number line. However, there is an interval between -128 and 0 where the function displays unexpected behavior, returning values close to 9.7. In this interval, the function seems to have a constant output.

[CODE]:
```python
def f(x):
    if x <= 0:
        return 9.7
    else:
        return 0.7
```

This code approximates the behavior of the function f(x) by using an if-else statement. For inputs less than or equal to 0, it returns 9.7, and for inputs greater than 0, it returns 0.7.