x86 Registers

Question 1

EAX

Answer 1

Accumulator; volatile (special); stores return value of functions; used w/ EDX in some mathematical calculations (mult/div)

Question 2

EBX

Answer 2

Base; non-volatile; no specific use; sometimes set to value (e.g. 0) throughout function to speed up calculations

Question 3

ECX

Answer 3

Counter; volatile; used to control loops; when calling a class, ECX is a pointer to the class; w/ EDX acts as first 2 parameters for “_fastcall” convention

Question 4

EDX

Answer 4

Data; volatile; stores function variables; used w/ EAX for mutl/div; w/ ECX acts as first 2 parameters for “_fastcall” convention

Question 5

ESI

Answer 5

Source Index; non-volatile; holds pointer to read location; counterpart w/ EDI

Question 6

EDI

Answer 6

Destination Index; non-volatile; stores storage pointers of functions (write locations)

Question 7

EBP

Answer 7

Base Pointer; base of stack (frame pointer); used to reference variables by offset from EBP

Question 8

ESP

Answer 8

Stack Pointer; non-volatile; top of stack; items pushed/popped increment/decrement ESP

Question 9

EIP

Answer 9

Instruction Pointer; not a GPR; points to memory address of next instruction to be executied