issues with row related in datatable in c#

Hai friends,I am new to this technology.Now I'm creating calculator application,In that i have to store result in a row of datable .Here i have 3 queries to discuss with you.

1.rows will not display in data table but store data in rows wise

2.every time result will store in  datatable first row only,2nd time if i press (ms memory store button) 1 st row data  shifted 2 nd row ...

3.I used clear() method to erase data in datatable  .after that if i press store button data wil be  store in nth row.(for exampledata table have 3 rows.after using clear() method.data store in a 4th row)

 

please clarify the above situations..

 

Thanks in advace