Assembly Language

Question 1

Mnemonics

Answer 1

Opcodes, like mov, add and inc

Question 2

Registers

Answer 2

Given names like eax, ebx for example.

Question 3

Labels

Answer 3

Used to represent memory addresses, like num1 for eaxmple

Question 4

Give an example of a line of assembly code that uses a mnemonic, register and memory address

Answer 4

mov eax, num

Question 5

EAX

Answer 5

Accumulator register - store calculations

Question 6

EBX

Answer 6

Base register - store a location

Question 7

ECX

Answer 7

Counter register - for loops purposes

Question 8

EDX

Answer 8

Data register - for random data

Question 9

How can you transfer data from one memory location to another?

Answer 9

You cannot move something directly from memory to memory -> has to be through registers.

Question 10

CF

Answer 10

Carry flag -> previous operation had a carry from the most significant bit.

Question 11

ZF

Answer 11

Zero flag -> previous operation had zero results.

Question 12

SF

Answer 12

Sign flag -> previous operation was positive (0) or negative (1)

Question 13

OF

Answer 13

Overflow flag -> previous operation was too big to fit in memory

Question 14

Jumps

Answer 14

Essentially calling a certain part of the code; allows loops (obsidian for examples).

Question 15

Mutual Recursion

Answer 15

-> sub1 calls sub2, sub2 calls sub1

Question 16

General case

Answer 16

-> bit that calls itself

Question 17

Terminating case

Answer 17

-> the bit that causes it to stop

Question 18

Nested Calls

Answer 18

-> tree structure of recursion
Factorial and fib can also be examples.

Question 19

Tail recursion

Answer 19

-> recursive call is the last statement that is executed by the function.

Question 20

Iterative v Non-Iterative

Answer 20

A function which calls itself, compared to a piece of code which doesn’t.

Question 21

scanf and printf

Answer 21

Both take arguments from the stack, given in the order which they are pushed onto the stack (FIFO). The format specifier normally has to be first, then the remaining information.
Scanf takes exactly 2, printf takes 1 or more.

Question 22

ESP

Answer 22

Stack pointer (points to top of stack).
In certain examples, we increase by 4 bytes to get next instruction, since stacks grow downwards.

Question 23

EIP

Answer 23

Instruction Pointer (points at programs next instruction).
In certain examples, we decrease by 4 bytes to get next instruction since it grows upwards.

Question 24

Calling Convention

Answer 24

Calling convention is an implementation-level scheme for how subroutines or functions receive parameters from their caller (via the stack).

Question 25

ret

Answer 25

Return value for subroutine.

Question 26

PROC and ENDP

Answer 26

Labels given at the start and end of a subroutine.

Question 27

call

Answer 27

Calls function.

Question 28

xchg eax, ebx

Answer 28

Swaps the data in these two registers around.

Question 29

movzx

Answer 29

Used to transfer the first character somewhere:
movzx eax, byte ptr [ebx]
Moves the first character of ebx into eax.