A “floating point number” is how computers usually represent numbers that are not integers — basically, a number with a decimal point. In C++ you declare them with float instead of int. A floating point exception is an error that occurs when you try to do something impossible with a floating point number, such as divide by zero.
for (i>0; i–;)
is probably wrong and should be
for (; i>0; i–)
instead. Note where I put the semicolons. The condition goes in the middle, not at the start.