Pros & Cons of putting all code in Header files in C++?

Question

You can structure a C++ program so that (almost) all the code resides in Header files. It essentially looks like a C# or Java program. However, you do need at least one

Answer 1

One disadvantage of your approach is you can't do parallel compilation. You might think you're getting a faster compile now, but if you have multiple .cpp files you can build them in parallel on either multiple core on your own machine or using a distributed build system like distcc or Incredibuild.