I have a code, and I do not understand it. I am developing an application which precision is very important. but it does not important for .NET, why? I don't know.

```
double value = 3.5;
MessageBox.Show((value + 1 * Math.Pow(10, -20)).ToString());
```

but the message box shows: 3.5

Please help me, Thank you.

## Best Solution

If you're doing anything where precision is very important, you need to be aware of the limitations of floating point. A good reference is David Goldberg's "What Every Computer Scientist Should Know About Floating-Point Arithmetic".

You may find that floating-point doesn't give you enough precision and you need to work with a decimal type. These, however, are always much slower than floating point -- it's a tradeoff between accuracy and speed.