Csci2450 Ch 5 Review Questions

Front 1

Which register (in protected mode) manages the stack?

Back 1

ESP

Front 2

How is the runtime stack different from the stack abstract data type?

Back 2

The runtime stack is the only type of stack that is managed directly by the CPU. For example, it holds the return addresses of called procedures.

Front 3

Why is the stack called a LIFO structure?

Back 3

LIFO stands for "last in, first out." The last value pushed into the stack is the first value popped out from the stack.

Front 4

When a 32-bit value is pushed on the stack, what happens to ESP?

Back 4

ESP is decremented by 4

Front 5

T/F. Only 32 bit values should be pushed on the stack when using the Irvine32 library.

Back 5

True

Front 6

T/F. Only 16-bit values should be pushed on the stack when using the Irvine16 library.

Back 6

False (you can push both 16-bit and 32-bit values)

Front 7

T/F. Local variables in procedures are created on the stack.

Back 7

True.

Front 8

T/F. The PUSH instruction cannot have an immediate operand.

Back 8

False (yes, it can, from the 80186 processor onward)

Front 9

Which instruction pushes all of the 32-bit general-purpose registers on the stack?

Back 9

PUSHAD

Front 10

Which instruction pushes the 32-bit EFLAGS register on the stack?

Back 10

PUSHFD

Front 11

Which instruction pops the stack into the EFLAGS register?

Back 11

POPFD

Front 12

Challenge: Another assembler(called NASM) permits the PUSH instruction to list multiple specific registers. Why might this approach be better than the PUSHAD instruction in MASM? Here is a NASM example:
PUSH eax ebx ecx

Back 12

NASM's approach permits the programmer to be specific about which registers are to be pushed. PUSHAD, on the other hand, does not have that flexibility. This becomes important when a procedure needs to save several registers and at the same time return a value to its caller in the EAX register. EAX cannot be pushed and popped because the return value would be lost.

Front 13

Challenge: Suppose there were no PUSH instruction. Write a sequence of two other instructions that would accomplish the same as PUSH EAX.

Back 13

Equivalent to PUSH EAX:
sub esp, 4
mov [esp], eax

Front 14

T/F. The PROC directive begins a procedure and the ENDP directive ends a procedure.

Back 14

True

Front 15

T/F. It is possible to define a procedure inside an existing procedure.

Back 15

False

Front 16

What would happen if the RET instruction was omitted from a procedure?

Back 16

Execution would continue beyond the end of the procedure, possibly into the beginning of another procedure. This type of programming bug is often difficult to detect!

Front 17

How are the words Receives and Returns used in the suggested procedure documentation?

Back 17

Receives indicates the input parameters given to the procedure when it is called. Returns indicates what value, if any, the procedure produces when it returns it to its caller.

Front 18

T/F. The CALL instruction pushes the offset of the CALL instruction on the stack.

Back 18

False (it pushes the offset of the instruction FOLLOWING the call)

Front 19

T/F. The CALL instruction pushes the offset of the instruction following the CALL on the stack.

Back 19

True

Front 20

T/F. The RET instruction pops the top of the stack into the instruction pointer.

Back 20

True

Front 21

T/F. Nested procedure calls are not permitted by the Microsoft assembler unless the NESTED operator is used in the procedure definition.

Back 21

False (there is no NESTED operator)

Front 22

T/F. In protected mode, each procedure call uses a minimum of 4 bytes of stack space.

Back 22

True

Front 23

The ESI and EDI registers cannot be used when passing parameters to procedures.

Back 23

False

Front 24

T/F. The ArraySum procedure (5.5.3) receives a pointer to any array of doublewords.

Back 24

True (it also receives a count of the number of array elements)

Front 25

T/F. The USES operator lets you name all registers that are modified within a procedure.

Back 25

True

Front 26

T/F. The USES operator only generates PUSH instructions, so you must code POP instructions yourself.

Back 26

False

Front 27

T/F. The register list in the USES directive must use commas to separate the register names.

Back 27

False

Front 28

Which statement(s) in the ArraySum procedure (5.5.3) would have to be modified so it could accumulate an array of 16-bit words?

Back 28

add eax, [esi] becomes ---> add ax, [esi]
add esi, 4 becomes ---> add esi, 2