Question

Can anyone explain if there is a difference between ftime() and time()?

Answer 1

ftime() is a (deprecated) POSIX function to get both seconds and miliseconds since epoch, time() is ISO C (and, thanks to that, ISO C++ as well) function to get seconds since epoch.

Quoting from ftime(3) man page:

This function is obsolete. Don’t use it. If the time in seconds suffices, time(2) can be used; gettimeofday(2) gives microseconds; clock_gettime(2) gives nanoseconds but is not as widely available.

Since you are writing C++, consider using std::chrono from C++11, which is native way to work with time intervals in C++.