Which Python object type is 'immutable', dictionary or tuple?
Tuples are immutable. While a dictionary can be modified, it's key must be an immutable data type.
What is the major problem with a SQL cross join?
With large tables, the result set may take more resources than allowed or available, possibly locking the user's working area until canceled, sometimes with need of a DBA's assistance.
In dealing with multiple C source files, why are function prototypes necessary?
It declares a function's parameter list, order and type, along with the function's return type for use in files other than the one it was defined in.