> even if they index arrays from 1 They don't have to! You can set the array index bounds to whatever you want. For example, real(8) A(0:n-1) real(8)

> even if they index arrays from 1 They don't have to! You can set the array index bounds to whatever you want. For example, real(8) A(0:n-1) real(8) w(-p:q) are both valid declarations and would be indexed by i=0,n-1 and i=-p,q respectively. If you're using gfortran compile with the "-fbounds-check" flag to save a lot of headaches!