Fast code is important, but without rigid rules a beginner programmer can write slow and unreadable code.
What is the best C standard that is explicit (not sugar coated with abstractions) and allows for assembly integration?

c89 forces you to declare functions first, and this separation between declaration and definition looks to me as very readable and explicit...
Also since it doesn't sugar coat anything, it allows for better understanding on what is under the hood (the assembly it generates).

Am I wrong? Hopefully an expert programmer can direct to the right path. Thank you.