Is it possible to automatically convert code from a low level language to a high level language?

Question

I have seen several applications that claim to convert Java code to valid C or even C++. Converting from a high level language to a low level language is possible, no doubt about it. At least in theory, can the reverse be done without any manual steps?

For instance:

• Converting Assembly to C or Machine Code to Assembly?

• Hardware Description Languages (HDL) to Assembly? (which ever is lowest?)

• C to C#?