I created a file a.mth with the contents of: PROG(x:=3, y:=4) [a:=1, b:=5] x+a I started Derive 6.10 I did File Open a.mth I did Simplify, Basic the x+a line and got x + 1 --- Fred J. Tydeman Tydeman Consulting [log in to unmask] Testing, numerics, programming +1 (775) 358-9748 Vice-chair of PL22.11 (ANSI "C") Sample C99+FPCE tests: http://www.tybor.com Savers sleep well, investors eat well, spenders work forever.