How to change value of EIP in ollydbg?

Question

I double clicked on EIP in register window,but seems un-editable.

Why is EIP special?How can I change it?

Answer 1

EIP is the instruction pointer. IE: the CPU's pointer to what code to run next. It's not a normal register in that you normally can't just mov stuff into it; it's only directly affected by instructions like jmp, call, int, etc (any instruction that causes code not to continue at the next instruction), as well as being moved with each instruction that gets executed.

Answer 2

Find the location you want to set your EIP to, right click and select "New Origin Here". This will reset the EIP to the new address. You can confirm this by inspecting the registers at the top right.

In addition to the reply above, the EIP is basically the pointer to where the current line of execution is. It's used to keep a record of which instruction the program is executing in memory.