MathCad 3.1 - File not supported

[emürer]

Hello

I have been using MathCad 3.1 for about 5-6 months as a tool for calculating and taking notes in physics, math, electrical engineering and so on. Most of my .mcdx documents contains a wide variety of text, calculations, plots and images. Usually I have no problems with MathCad. However i cannot open a specifik file containing valuable notes on electrical and magnetic fields. The content is valuable to me, mainly because my exam on the subject is in 2 days, but I can get by without.

But I would really like to know the cause of this problem, because if this is a consistent problem and i will, for no appearent reason, loose some files every now and then, then i cannot continue using MathCad. It could completely ruin and exam.

The nature of the problem:
I have not opened the file for at least a month. It worked fine the last time though. Now when i try to open it, it says "The file type is not supported" and it points to a log file. After searching for a solution on the internet i found that a mcdx file is actually a zip file. However i cannot open it as a zip file. Not when it is as .mcdx file and not when i rename it to a .zip file. Winzip and Winrar both reports that the file is either not supported or damaged.
I then tried using Diskinternals ZIP repair and also Zip Rapair Pro to repair the file. Both programs does not register any files within the zip(even though its size is over 6mb) file and just spits out empty ZIP files(size 0 bytes). 

Trying to open the file, with either zip or mcdx extension, in notepad/wordpad doesent work either. I didnt expect it too either. It just shows thousands of blank pages. This is the extent of my mcdx related knowledge. At this point i do not expect to ever open this file again, however i would like to know possible causes, so that I can either avoid this problem in the future or reevaluate if MathCad is worth the risk of potential lost data. It might be worth mentioning that i am using Dropbox to synchronize my laptop and desktop, however this has never corrupted a file before, MathCad file or not.

Both the mcdx file and the log file is attached to this post. If anyone can come up with a possible answer I would be very grateful.

Many thanks
Emil

[Werner_E]

I remember that a similar effect was reported here not too long ago. As far as I remember there could no cause for the damage be found.

->Re: 'the file type is not supported.'

The bad news are that your file simply consists of 6421200 bytes and every single one of them is a NUL byte. So there is no information in this file which could be recovered. Looks like the file was damaged the last time you saved it from within Prime.

Unfortunately (on contrary to Mathcad 15 and below) Prime does not offer a feature like autosave, making a backup of the file in use every few minutes. So unless you have a backup of the file somewhere else, the information which was in the file is lost completely.

WE

[RichardJ]

As Werner says, your file is trashed. However, if it was synced with Dropbox you can roll back to a previous copy of the file.

[emürer]

Yeah your answers are kinda what i expected. I just hoped for maybe some reason(which I can avoid in the future) to why this has happened. The Dropbox trick does not apply for me since one has to pay for the option to "roll back" the file, which I do not pay for(the life of a poor student...). No matter. I just had to redo all the work, which I did today. 32 pages of calculations + notes in one go today. Kinda dizzy now... I hope this issue will not happen again in the future, especially this close to an exam. This time i also made a PDF copy, just to be sure

Thanks for the input anyway

/Emil

[RichardJ]

This is the third time (at least) that this problem has been posted. One solution (or workaround; the solution is for PTC to fix the problem!) is to make your own regular backups by copying your Mathcad files into a dated folder.

I had forgotten that the rollback was only available with the paid up version of Dropbox.

[VladimirN]

I always make a copy of my work files by using the archiver (WinRAR/7-Zip).

[StuartBruff]

Another possibility is set up System Protection to automatically take backups of changed files.  You should then be able to see the previous versions and recover them.

Stuart

[VladimirN]

Stuart,

Can we set this option only for certain types of files (.mcd, .xmcd, .mcdx)?