Hello! In my previous mail to this mailing list yesterday I had an 'Internal Compiler Error'. Now I changed the last few lines to: For i:=1 to II DO if h_c[i,j,k]=1 then begin if dx[i]<0 then test:=-(exp(ln(-dx[i])*(-1))) else test:=(exp(ln(dx[i])*(-1))); du:=abs((0.5*(UU[i,j,k]+UU[i+1,j,k]))*test); This works! And it means to me that the division by a 'Single'-Variable is not always allowed in GNUPascal. Is this true (or is there a bug) ?? Hope somebody can helpme Thanks for your answers Matthias _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/ - Matthias Friedrich - email: mafri@ipg.uni-freiburg.de