sorry if this has already been asked, but in day of the doctor, when the three doctor's are locked up it is said that the sonic could open the door, but would take hundreds of years to do the calculations. Then they say John hurt can set it, and it will carry on through the different doctors screwdriver's since it is the same screwdriver with different casing.

my question is, how can this be so when matt smith clearly broke the screwdriver in the eleventh hour then the tardis replaced it for him with a completely new one

It's stored on the software, so I imagine it would be backed-up in the TARDIS.

Didn't they say the software was the same not the actual screwdriver?

Each time a new screwdriver was made by the TARDIS the previous software including any ongoing processes (such as these calculations) would be added onto it.

I took it to mean the actual same screwdriver in different casing, as I thought it needed to be for the program to keep running, but yeah the tardis backing up it's data and whatever program's it's running makes sense. thanks all for the clarification. unusual to post a question and get an easy answer this quickly (without a mile long thread of debating, i mean) cheers.

Don't speak too soon

Don't forget that the Tenth Doctor's Sonic was destroyed in Smith and Jones so he got himself a new one at the end of the story, it just happened to look the same as the previous one.

and Matt's got broken again in the Christmas Carol episode!
I think that when the Sonic recharges, like others have said, it backs up to the TARDIS!
We can do the same with our phones/tablets and computers, its exactly the same principle.

We've known since The Snowmen that the TARDIS is a cloud.

lol well yes in a way

thought david tennant replaced his at least once, but couldn't remember when it was

As Basil Brush would have said : "Boom, Boom!"

Give the number of settings and presets the Doctor's added to his screwdriver over the years, he'd have to back them up. Imagine having to re-enter all the settings for barbed wire all over again!