What is the address of the first SFR (I/O Register)​

The Special Function Register (SFR) is the upper area of addressable memory, from address 0x80 to 0xFF.

Explanation:

The Special Function Register (SFR) is the upper area of addressable memory, from address 0x80 to 0xFF.

Reason -

A Special Function Register (or Special Purpose Register, or simply Special Register) is a register within a microprocessor, which controls or monitors various aspects of the microprocessor's function.

maybe when you are listing people names in a job.

i am not 100% sure

the answer to your question would be something called hertz. the unit of measurement called a hertz, which is one cycle per second, is used to measure clock speed. within one cycle, your computer processes, refreshes, or updates itself to the changes that it is going through. in the case of computer clock speed, one hertz equals one tick per second. the clock speed of computers is usually measured in megahertz (mhz) or gigahertz (ghz)