Hi I don't call this self modifying. Where you have a port command like the 8080 and you overwrite the port address before executing, now that is self modifying. Something like over writing an add instruction with a subtract would qualify as self modifying. Placing the address at the beginning is no different than pushing the address onto a stack, other than that it isn't reentrant ( with out extra code and then not for interrupts ). The first address isn't code, it is a variable space. The executed code never changes. My Nicolet uses the entry address saving method. In any case, I never understood the stigma of using self modifying code. It does require careful documentation if it is expected to be maintained. There is no reason why it can't be as robust as any other code if done properly. I suspect it was used as a sales talk when someone was trying to pitch their version of code to be better than someone else's. Such things as overlays would qualify as more risky uses of self modifying code but that is done without mention. Dwight