Week Four

Question 1

How would you order this four-byte sequence 928A8A57h stored in consecutive memory cells in a little-endian architecture into a big-endian architecture?

Answer 1

57 8A 8A 92

MSB –> LSB

Question 2

How would you order this two-byte sequence C1ACh stored in consecutive memory cells in a little-endian architecture into a big-endian architecture?

Answer 2

AC C1h

MSB –> LSB

Question 3

How would you order this four-byte sequence 50 8A 8A 92h stored in consecutive memory cells in a big-endian architecture into a little-endian architecture?

Answer 3

92 8A 8A 50h

LSB –> MSB

Question 4

When values are received by a called subroutine/function, they are called _________.

Answer 4

parameters

Question 5

High-level languages always pass arrays to subroutines by value.

Answer 5

False

Question 6

What are the order of steps for creating a stack frame?

a. passed arguments are pushed on the stack
b. if there are local variables, ESP is decremented to reserve space for the variables on the stack
c. if any registers need to be saved they are pushed on the stack
d. the subroutine is called, causing the subroutine’s return address to be pushed on the stack
e. as the subroutine begins to execute, EBP is pushed on the stack
f. EBP is set equal to ESP. From this point on EBP acts as a base reference for all of the subroutine parameters.

Answer 6

A - D - E - F - B - C

Question 7

When an argument is passed by value, a copy of the address is pushed on the stack.

Answer 7

False

Question 8

A stack frame is?

Answer 8

The area of the stack set aside for passed arguments, subroutine return address, local variables, and saved registers.

Question 9

Passing by reference requires dereferencing a parameter’s offset from the stack inside the called procedure.

Answer 9

True

Question 10

A subroutine’s stack frame always contains the caller’s return address and the subroutine’s local variables.

Answer 10

True

Question 11

What advantages do stack parameters have over register parameters?

Answer 11

Stack parameters reduce code clutter because registers do not have to be saved and restored.
Stack parameters are compatible with high-level languages.

Question 12

Another name for a stack frame is?

Answer 12

Activation record

Question 13

Assuming that a procedure contains no local variables, a stack frame is created in what order of actions at runtime?

Answer 13

arguments pushed on stack; procedure called; EBP pushed on stack; EBP set to ESP

Question 14

How would you define a local variable array consisting of 50 signed words?

Answer 14

LOCAL wArray[50]: SWORD

Question 15

Values passed to a subroutine by a calling program are called _____.

Answer 15

arguments

Question 16

Which action must take place inside a procedure to reserve space on the stack for two doubleword local variables?

Answer 16

after MOV EBP,ESP, subtract 8 from the stack pointer (ESP)

Question 17

An argument passed by reference consists of the offset of an object.

Answer 17

True

Question 18

Local variables are created by adding a positive value to the stack pointer.

Answer 18

False (subtracting from EBP)

Question 19

What general types of parameters are passed on the stack?

Answer 19

Value and reference arguments

Question 20

What is the procedure entry code generated by MASM when the LOCAL directive is used to declare a doubleword variable?

Answer 20

push ebp
mov ebp,esp
sub esp,4

Question 21

Which offers a more flexible approach, passing arguments to procedures in registers, or on the stack?

Answer 21

on the stack yo

Question 22

When an argument is passed by value, a copy of the address is pushed on the stack.

Answer 22

False

Question 23

What does the RET instruction do?

Answer 23

When the procedure is ready to return, its RET instruction pops the 4-byte return address from the stack into the instruction pointer. The CPU executes the instruction in memory pointed to by EIP (instruction pointer register).

Question 24

Is this a valid instruction?

mov [edx], [eax]

Answer 24

No, there are no memory to memory instructions. Both of these instructions point to a memory address.

Question 25

The stack pointer is _____ when we push things on, and _____ when we pop things off

Answer 25

decremented - push

incremented - pop

Question 26

In the Intel x86 architecture, the register that always points to the next instruction to be executed is the?

Answer 26

EIP

Question 27

Please sort the following types of memory according to their relative access speeds, slowest to fastest.

a. main memory
b. cache
c. registers
d. optical disk

Answer 27

D - A - B - C