>C and assembly are all you need to know.
Neither will do for designing digital logic.
We use HDLs to create the logic that makes the instructions. Instructions are way too high in the stack.
Verilog sucks and System Verilog makes amends, but neither is worthy of VHDL.
VHDL's syntax sucks because it's based on ADA. But the execution model makes sense, unlike Verilog.
C will fail to help you make a chip. System C exists, but seriously, don't go there.
MyHDL is a python HDL which should be awesome, but it isn't.
But C is most certainly not all I need to know.