Hi, 1)Are -O and -O1 flags equal? 2) What happens internally when -O1/-O flag is used? I have been searching gcc internal manuals. But I could not locate. Where can I find it.Any help please. Thanks in advance. ___________________________________________________________ The all-new Yahoo! Mail goes wherever you go - free your email address from your Internet provider. http://uk.docs.yahoo.com/nowyoucan.html