Decimal function

I need a function that allows a positive number with a decimal point, to be rounded up or down. For example:

2.3 would be 2
2.7 would be 3



I also need a function that, when a user inputs 4 numbers, that the numbers are only allowed if they are positive. I have figured out how to have the user input 4 numbers but can't figure how to assure that they are positive and when they're aren't, an error message informs the user.

Any help would be appreciated
Thanks

just check the mantissa and reassign the number appropriately...