Direct I/O reads/writes from C programs

[Dave]

How does one directly access an I/O address from C?

For example if I want to write a char to port 0x80 (or read a char from a
port) what is the statement? 

How about memory mapped I/O? If one wants to directly access a specific
memory address what are the statements? 

Is direct I/O and direct memory access part of ANSI C?

I have an embedded X86 project that has to directly access the hardware. I
would prefer doing it in C rather than ASM.

TIA
Dave