# How to use the old kernel in a newer version of MMa

I am used to the conveniences of MMA 11.3 such as: can undo some times, autocomplete codes, and so on, however I have to run some functions in the version 5.2. So I installed Mathematica V11.3 and V5.2 in my PC at the same time. Now I want to know if I can run my old functions through MathKernel 5.2 in the notebook 11.3; If yes, how can it be done? It will be better if one or two practical examples are provided. Thanks.

If you can not find the v5.2, you can demonstrate the process by using v11.3 ,v12, or any other different versions you can find.

BTW, I have read the following links? but they failed to solve my problem.

Executing code in v.5.2 kernel from within v.7.01 session through MathLink

I needn't interact the results of each other between the two versions, I only want to combine the MathKernel 5.2 and the notebook 11.3 (if possible, you can cut off the MathKernel 11.3)

Are later versions of the Front-End compatible with older Kernels?

Not give examples how to make it come true.

• I would recommend putting the effort into modernizing your code rather than trying to get this to work. It's probably a better use of your time. – ktm Apr 9 at 13:17
• @ktm, thanks for your attention, but some functions can not be modernized, check the link please mathematica.stackexchange.com/questions/195465/…. – likehust Apr 9 at 13:24
• Have you tried adding a new kernel in the kernel configuration options? This does work in general. But with 5.2? I would be very surprised if there weren't many issues ... – Szabolcs Apr 9 at 13:28
• @likehust Change the path of the kernel executable to point to 5.2's kernel and change -wstp to -mathlink. No guarantees that it will work with such an ancient version ... You can also check the form of the kernel launch command in 5.2's kernel config options and use that in 11.3. – Szabolcs Apr 9 at 13:48
• However, if your goal is to write code for 5.2, you should be using 5.2 ... the limitations are the price to pay. I agree with ktm that the reasonable way forward is to modernize the code and simply not use 5.2 anymore. The kernel of the most recent version is available for free as the "Wolfram Engine". One can also use the new version in the cloud. – Szabolcs Apr 9 at 13:51