After doing this division

Hello,
The TI84 has two commands fPart( and int(. They are accesible by the sequence

[MATH][NUM][4] fPart(
[MATH][NUM][5] int(

Once you select the command it shows on home screen> you complete the command and press [ENTER]

Let the number be 15.78

int(15.78) [Sto->] [ALPHA] [F] stores the inter part of the number (15) in variable F. Similarly
fPart(15.78) [STO->] [ALPHA] [I] stores 0.78 in variable I.

Hope it helps

You may be able to find a program online that will automatically do what you want however if you don't have to do this too often you can just manually set "1" to a variable via the "STO-->" button (right above the "on" button-- select the value, pres sto-->, alpha and whatever variable you want) and set the ".75" to a variable.

Finding a program may be difficult for this type of program because you're trying to separate a whole number (essentially looking for a whole number and the remainder). You could always write a program for yourself but as I said before it might be a bit difficult.