Which register stores the address of the first data element stored onto the stack?

Which register stores the address of the first data element stored onto the stack?

• A. Extended Stack Pointer (ESP)
• B. Extended Instruction Pointer (EIP)
• C. Extended Source Index (ESI)
• D. Extended Base Pointer (EBP)

Answer: (D)

The base pointer is used as a stable reference to the current stack frame. In x86, when a function is called, the prologue typically saves the old frame pointer and then sets the base pointer to the current top of the stack. This establishes a fixed starting point for that function’s stack frame, so data like parameters and local variables can be accessed using consistent offsets from this address. ESP, by contrast, moves as data is pushed and popped, so it isn’t a fixed reference for the first data element in the frame. EIP tracks the next instruction to execute, and ESI is a general-purpose index register. Thus, the base pointer stores the address of the start of the current stack frame.

The base pointer is used as a stable reference to the current stack frame. In x86, when a function is called, the prologue typically saves the old frame pointer and then sets the base pointer to the current top of the stack. This establishes a fixed starting point for that function’s stack frame, so data like parameters and local variables can be accessed using consistent offsets from this address. ESP, by contrast, moves as data is pushed and popped, so it isn’t a fixed reference for the first data element in the frame. EIP tracks the next instruction to execute, and ESI is a general-purpose index register. Thus, the base pointer stores the address of the start of the current stack frame.