Instruction pointer

There is one more special register that cannot be used for data storage--EIP (IP in the real mode or RIP in the long mode). This is the instruction pointer and contains the address of the instruction after the instruction currently being executed. All instructions are implicitly fetched from the code segment by the CPU; thus the full address of the instruction following the one being executed should be described as CS:IP. Also, there is no regular way to modify its content directly. It is not impossible, but we can't just use a mov instruction in order to load a value into EIP.

All the other registers have no special meaning from the processor's perspective and may be used for any purpose.