What does these errors mean? Assembly Language

Question

; This program checks for even or odd parities inside of an array. Displays 1 if even or 0 if odd.

Include Irvine32.inc

TRUE = 1
FALSE = 0

.data

str1 BYTE "Even Parity", 0
str2 BYTE "Odd Parity", 0
str3 BYTE "The block of data under checking is: ", 0

array1 BYTE 1,0,1,0,0,0,1,0,0,1
array2 BYTE 1,0,0,0,0,0,1,0,0,1 
; declares two 10-bit arrays

.code
main proc

call Clrscr                 ; Clears the screen

mov esi, OFFSET array1      ; Pass address

mov ecx, LENGTHOF array1    ; Pass length

call Display                ; Display on Console
call Parity_Check
cmp eax,0
je L1                       ; if EAX = 0 then odd
mov edx, OFFSET str1
call WriteString            ; Write str1
call Crlf
L1:
mov edx, OFFSET str2
Call WriteString            ; Write str2
call Crlf
call Crlf                   ; Check if array2 is even or odd

mov esi, OFFSET array2      ; Pass Address

mov ecx, LENGTHOF array2    ; Pass length

call Display                ; Display on console
call Parity_Check
cmp eax, 0
je L2                       ; if eax = 0 then odd
mov edx, OFFSET str1
call WriteString            ;Write str1
call Crlf
L2:
mov edx, OFFSET str2
call WriteString            ; Write str2
call Crlf
call Crlf

    invoke ExitProcess,0
main endp


Parity_Check PROC USES eax ecx esi edi  ;Returns 1 if even 0 if odd

mov edi, 0          ; array pointer 0

L1:
xor [esi], 0        ; Xor data bits
inc esi             ; points to next bit
loop L1             ; continue loop
jpe L2              ; jumps to L2 if even
jpo L3              ; jumps to L3 if odd
L2:
mov eax, TRUE       ; copies 1(true) to eax
jmp L4
L3: 
mov eax, FALSE      ; copies 0(false) to eax
L4:
ret

Parity_Check ENDP
Display PROC USES esi ecx edx   ; Displays array elements

mov edx, OFFSET str3
call WriteString                ; Writes str3
L1:
mov eax, [esi]                  ; Store array in eax

call WriteDec                   ; Write EAX
inc esi                         ; Point to next item in array
loop L1                         ; Continue Traversing 
call Crlf
ret

Display endp
end main

I can't figure out why I am getting an error for my XOR and a masm.target (file) error. The XOR says "Invalid instruction operand" while masm.targets error brings me to that file.

masm.targets is the file name, the error code is MSB3721 on line 50 column 5 (again it brings me to another page so I am assuming something is wrong with my MASM setup?). Any help with either of these?

Answer 1

array1 BYTE 1,0,1,0,0,0,1,0,0,1
array2 BYTE 1,0,0,0,0,0,1,0,0,1
; declares two 10-bit arrays

You actually declared 2 arrays of 10 bytes each.

xor [esi], 0        ; Xor data bits

MASM will complain for not knowing the size of this xor operation. Just write it like xor byte ptr [esi], 0

jpe L2              ; jumps to L2 if even
jpo L3              ; jumps to L3 if odd

Both these parity related jumps will be based on the parity from incrementing the address in ESI. They don't reflect any parity value you got from testing the bytes in the array! Here's a routine that does:

Parity_Check PROC USES eax ecx esi ;Returns 1 if even, 0 if odd
 mov al, 0    
L1:
 add al, [esi]
 inc esi             ; points to next byte
 loop L1             ; continue loop
 test al, 1
 jnz L3              ; jumps to L3 if odd
L2:
 mov eax, TRUE       ; copies 1(true) to eax
 jmp L4
L3: 
 mov eax, FALSE      ; copies 0(false) to eax
L4:
 ret
Parity_Check ENDP

In your Display procedure you forgot what is the true size of the array elements.
Change this

mov eax, [esi]                  ; Store array in eax

into

movzx eax, byte ptr [esi]

Answer 2

You're using a notation that treats [esi] as a reference, what you probably intended to do was xor esi, 0 -- but even so, such an operation isn't really meaningful (esi will remain unchanged.)

If you meant to modify the memory location identified by the value in 'esi' you may want to consider moving it into a register before the 'xor' operation, since I do not believe xor operates on memory operands (i could be mistaken, it has been a while for me.)