In a modern x86 processor, an instruction pointer register (also known as the flag register or program counter) is an area of memory that represents the address of the instruction that is currently being executed. It automatically increments upon execution, but is not accessible directly. Generally, an instruction pointer register (IP register) is set to 0 when there is no overflow or odd number of aEURoe1aEUR bits in the operand.
In most processors, an instruction pointer is the address of the next instruction. It points to the top-most part of the Stack, which is a memory location for temporary data. It is also used for storing instructions, which means it must be present in the IP register during instruction execution. If a program executes a code that includes an IP register, the instruction will be executed at the address indicated by the CS-IP pair.
The Instruction Pointer Register is one of the many parts of the CPU, which also includes the accumulator, data register, and index register. These registers serve the purpose of memory processing. Some experts consider registers to be the “most important part of a CPU” because of their crucial role in processing memory. The Instruction Pointer Register holds the current machine instruction that is queued to be executed. It’s important to understand how the IPS works so that you can design your computer to utilize its full potential.
The EIP is also used to identify instructions. PIE instructions never reference global variables directly, instead, they use deltas relative to the next %rip. This is because relative addresses work independent of starting point. Non-PIE instructions may write movq g, %rax, where g is a fixed address. For this reason, it’s essential to understand how EIP works and how to protect yourself with it.
The instruction pointer is used to locate data segments. It serves as a pointer to the memory for each segment. The address for a segment is determined by multiplying the 16-bit number in the DS register by 16. Therefore, the DS and BX offsets equal 12357h. Then, the instructions are executed. There’s one last thing to know about the Instruction Pointer Register.