Fetch and Execute Cycle

Example of Fetch and Execute
TASK: Add two numbers FF + 1 = ?
Program Algorithm :
Step 1.
Step 2.
Step 3.
Step 4.
Step 5.
Move number FF into Accumulator (AL)
Move number 01 into register BL
Add BL to AL leave the result in AL
Move contents of AL to memory address 300h
Stop
Machine code in memory (assuming starting location :000) :
Address 0 1 2 3 4 5 6 7
:000 B0 FF B3 01 00 D8 A2 00
:008 03 CD 20 X X X X X
Assembly Program Listing
MOV AL, FF
Machine Code
B0 FF
MOV BL, 01 B3 01
ADD AL, BL
00 D8
MOV [300], AL A2 00 03
INT 20 CD 20

Register and Memory Contents Map
PC AX BX :301h :300h
0 0 0 0 X X X X X X X X X X X X
AH AL BH BL
MOV AL, FF
(immediate addressing mode)
0 0 0 2 X X F F X X X X X X X X
MOV BL, 01
(immediate addressing mode)
0 0 0 4 X X F F X X 0 1 X X X X
ADD AL, BL
0 0 0 6 0 1 0 0 X X 0 1 X X X X
MOV [0300], AL
(direct addressing mode)
0 0 0 9 0 1 0 0 X X 0 1 X X 0 0
INT 20

Question : What corrections needed to get the correct
answer in memory locations 300h and 301h ?
Use MOV [0301], AH 88 26 00 03
or
16 bit move : MOV [0300], AX A3 00 03
Problem 1: Modify the code to add two arbitrary bytes .
Problem 2: Modify the code to add two arbitrary words
using 16 bit ADD instruction.
Problem 3: As problem 2, but use a 8 bit ADD instruction.
Hint: Need to take into account the carry bit and use ADC (add with
carry) instruction for the addition of high bytes.