Q. I would like to be able to put a programmable lock on my Commodore 64 so that, whenever I turn it on, I would have to INPUT the correct password to be able to use it.

Can you print a listing that does this?

Trevor O' Grady
Co. Kerry, Ireland

A. No, and if you think about how a computer works you should be able to work out why. Computers have Read Only Memory and Random Access Memory - you can program the latter, but not the former, and anything you put into RAM is lost when you switch the power off.

When you power up your C64, the ROM takes over and goes through the same routines every time you switch it on. In order to do what you have in mind you have to change those routines, and you can't do this through software alone.

So if you want a password on your C64 badly enough, this is what you do:

First, copy the ROM into RAM, then examine the C64's start-up routines. While the ROM is in RAM you can rewrite the start-up routines so that it demands an INPUT part-way through them. Once it does this to your satisfaction, it's just a matter of blowing an EPROM and switching the C64's ROM for that new EPROM.

Unless you're going to get into ROM disassemblies and EPROM programming in a big way, it isn't really worth the bother. Life would be much easier if you just bought a lockable desk.