>Any C compiler that cannot find "stdlib.h" has issues. I have repaired my VS2019 installation & kept it up to date (I normally use it for C# only). I cannot uninstall and then re-install using the same license - only one installation per key. Somehow, some setting in VS2019 has got 'installed/misplaced/corrupted' that is telling VS2019 to look for stdlib.h where it isn't. As I mentioned, C/C++ is alien to me but I had managed to compile v3.33 earlier on (but can no longer do that either). I'll try Keith's suggestion [9] next.