I don't have any software that's been in use for 100 years but I have a couple of items in the 15-20 year range. About the only thing that they have in common

I don't have any software that's been in use for 100 years but I have a couple of items in the 15-20 year range. About the only thing that they have in common is that they started with the thought: "I'll just knock this up in 5 mins then come back and do it properly when I have the time".