I'm sure there's no 'hard and fast' rule, but I gotta ask...

[circuitpro]

Assume your PIC has been programmed, and it's I/O pins are doing their thing. Is there any rule about what happens to these I/O's when you reprogram the PIC? To my surprise mine seem to hold their state during the programming, and then do what they're suppose to again once the new program has started. The reason I mention it is this PIC is controlling a large security system, and holding things locked. I was afraid that during programming an update, the pins might/would go high or open collector or ??? and unlock the locks, but it isn't doing that, and I'm pleasantly surprised.