I'm using Visual C++ 2008 Express Edition and when i debug code: double x = 0.2; I see in debugging tooltip on x 0.20000000000000001 but: typedef numeric_limits< double > double_limit; int a = double_limit::digits10 gives me: a = 15 Why results in debugger are longer than maybe ? What is this strange precision based on ? My CPU is Intel Core 2 Duo T7100