Category: How-To

.386
.model flat,stdcall
.stack 4096
ExitProcess PROTO, dwExitCode:DWORD

.data
mon = 1				;symbolic constants
tue = 2
wed = 3
thurs = 4
fri = 5
sat = 6
sun = 7
;puting symbolic constants in an array of DWORDS
week DWORD mon,tue,wed,thurs,fri,sat,sun		;DWORD = 4 Bytes										
week2 WORD mon,tue,wed,thurs,fri,sat,sun		;WORD = 2 Bytes
week3 BYTE mon,tue,wed,thurs,fri,sat,sun		;BYTE = 1 Byte

.code
main PROC

	;week 1
	;in order to reach the next element of the array
	;we must inciment by 4 because it is a DWORD array 
	;32 bit registers should be used
	mov eax, week							 	  ;eax = 1
	mov ebx, week+4								;eax = 2
	mov ecx, week+8								;eax = 3
	mov edx, week+12							;eax = 4

	;week2
	;in order to reach the next element of the array
	;we must inciment by 2 because it is a WORD array
	;16 bit registers should be used
	mov ax, week2						 		  ;ax = 1
	mov bx, week2+2								;bx = 2
	mov cx, week2+4								;cx = 3
	mov dx, week2+6								;dx = 4

	;week3
	;in order to reach the next element of the array
	;we must inciment by 1 because it is a BYTE array'
	;8 bit registers should be used
	mov al, week3						 		  ;al = 1
	mov bl, week3+1								;bl = 2
	mov cl, week3+2								;cl = 3
	mov dl, week3+3								;dl = 4

INVOKE ExitProcess,0
main ENDP

END main

.386
.model flat,stdcall
.stack 4096
ExitProcess PROTO, dwExitCode:DWORD

.data 
;EQU directive defines a symbol by either an integer or text
;EQU directive makes the symbolic constant so it can't be redefined.
str1 EQU <"apple",0>		
str2 EQU <"orange",0>		 
str3 EQU <"grape",0>
str4 EQU <"melon",0>

var1 BYTE str1
var2 BYTE str2
var3 BYTE str3
var4 BYTE str4

result DWORD 1234567h
.code
main PROC
	mov eax,0                       ;clarity purposes
	mov ebx,0
	mov edx,0
	mov ecx,0

	mov al, var1                    ; al = 61h which is 'a' in ascii
	mov bl, var2+1                  ; bl = 71h which is 'r' in ascii 
	mov cl, var3+2                  ; cl = 61h which is 'a' in ascii 
	mov dl, var4+3                  ; dl = 6Fh which is 'o' in ascii 

INVOKE ExitProcess,0
main ENDP
END main

.386
.model flat,stdcall
.stack 4096
ExitProcess proto,dwExitCode:dword

.data
sum DWORD 0
remainder DWORD 0

num1 WORD 5
num2 word 12
num3 word 10
symbolicCon = 8
.code
main proc
; sum = (13 + 6) - 5
mov eax,13 
add eax,6 
sub eax,5 
mov sum,eax               ;Sum = 16 eax= Eh

; sum = (13h + 6h) - 5h
mov eax,13h               ;19 
add eax,6h                ;6
sub eax,5h                ;5
mov sum,eax               ;Sum = 20 eax = 14h

; sum = (44 / (2 * 11)) + 7
; learn more about the mul and div instruction in chapeter 7.3
mov eax, 2
mov ebx, 11
mul ebx                   ;eax = 22 
mov ebx, 44
xchg eax, ebx             ;eax = 44 ebx = 22
div ebx                   ;eax = 2
add eax, 7
mov sum, eax              ;Sum = 9

; sum = (7 * 5) / 4
mov eax, 7
mov ebx, 5
mul ebx
mov ebx, 4
div ebx
mov sum, eax              ;Sum = 8
mov remainder, edx        ;Remainder = 3

; sum = ((num1 * num2) / num3) - symbolicCon
mov ax, num1
mul num2
div num3
sub ax, symbolicCon
mov sum, eax              ;Sum = -2 Eax = FFFE
invoke ExitProcess,0
main endp
end main

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