Edit protection for fomula's in sover app

[bhennink]

This would be high on my list and could be something that is pretty easy to realize.
Just have an option in the solver app to lock/unlock the equationset. Could be just a semaphore I think.
If this was in the prime would not have hesitated to get one.
Coming from the HP27S the possibility to have multiple 'solver apps' with named eqution sets is really a big step forward. But most times these equations are not the simple A+B=C/D type. Then it is pretty frustrating if you by accident lose an equation. I did not find a CTRL-Z either.

Also testdriving a HP50 which I borrowed from someone who only does basic calculations. But I get the feeling there will be no bond between us. I get lost every time and many things are not intuitive for me