sorry, i may have no clarified what i was asking. i have to use an infinte series to determine the value of e. thats basically the basis of the program..but i did try that new equation you gave, but it was giving me an error since y wasn't defined before it used itself in the equation. (i.e. e^(x)=1+(x/1!)+(x^(2)/2!)+.... ) using 20 terms. then the program calculates the error by subtracting that number from the defined value of e. any input would be much oblidged~ thanks again.