[bluGill]

Algorithms and data structures come BEFORE dropping to c.

These days it is rare that you can beat your compiler with hand machine code, and even if you can it isn't worth it because the difference is typically small and only applies to one specific machine.

Of course once in C you can often think about memory locality and other cache factors that higher languages hide from you.

[pjmlp]

Many applications still start in C, there is no dropping into C.