How to use classes from another d files

[Arun Chandrasekaran]

On Tuesday, 22 October 2019 at 17:34:51 UTC, Vinod K Chandran 
wrote:
> Hi all,
> I am new to D. But some fair experience with vb.net. I was 
> playing with D classes.  I wrote a class in a D file.
> The file name is "classFile.d"
> ```D
> class TestClass {
>
> [...]

What you are seeing is a linker error. Build it as follows:

dmd caller.d classFile.d

Unrelated, first line of classFile.d needs be `module classFile`