What is the difference between float and double?

Question

I\'ve read about the difference between double precision and single precision. However, in most cases, float and double seem to be interchangeable,

Answer 1

If one works with embedded processing, eventually the underlying hardware (e.g. FPGA or some specific processor / microcontroller model) will have float implemented optimally in hardware whereas double will use software routines. So if the precision of a float is enough to handle the needs, the program will execute some times faster with float then double. As noted on other answers, beware of accumulation errors.