Regardless of whether or not it's a good idea to solve your problem in the way that you did, the error "Unresolved External" means you referenced a symbol (calloc) that the linker didn't recognize.

Make sure you are including all the header file(s) you may need to include for calloc to be recognized, and that you are linking in any libraries or objects that may also need to be linked into the final software. The manual or help files for your compiler should indicate which headers and/or libraries need to be included to use a given function.

I personally have never used dynamic memory on the 8052. Rather than trying to make calloc work, I'd look at a way to solve the problem without using dynamic memory.

Good luck,
Craig Steiner