It still appears to me that you're chasing a phantom problem, and the more you chase the more you convince yourself that you've got a solution to this phantom problem.
Your _ftod does NOT convert a float to a double. It converts a string to a double. The string is created using the original float with reduced precision, which in this case matches the output seen using the watch window in VC++.
Here's what you said at the start of the thread:
Hi, i have a problem with converting a float to a double.
I want the double value to be the exact same value as the float value
You haven't achieved that with your solution, you've just fooled yourself into thinking you've achieved it because for the single value that you're testing it with it matches what you (erroneously) expect to see.
There is no cast required to go from float to double, you can simply assign the float to the double and it will have the same value. You're using C; in C this much is guaranteed to be true. Assignment will result in the two having the same value. No conversion function is required. You're chasing a phantom problem that doesn't exist because when you examine the float in the watch window it displays the value with less precision than it displays the double.
You're wasting your time :-)
