When $y(i+1)=y(i)+hf(t,y)$
if step size $h$ is small then this method is expected to occur round off error
thus we transhape this Euler form to $u(i+1)=u(i)+hf(t(i),u(i))+o(i+1)$
which $o(i)$ is round off error of each $u(i)$
then if we encounter the problem with absolute error of $|y(i)-u(i)|$ how we resolve this problem if round off error is infinite decimal point?