47 lines
1.3 KiB
NASM
47 lines
1.3 KiB
NASM
bits 32 ; assembling for the 32 bits architecture
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; declare the EntryPoint (a label defining the very first instruction of the program)
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global start
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; declare external functions needed by our program
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extern exit ; tell nasm that exit exists even if we won't be defining it
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import exit msvcrt.dll ; exit is a function that ends the calling process. It is defined in msvcrt.dll
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; msvcrt.dll contains exit, printf and all the other important C-runtime specific functions
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; our data is declared here (the variables needed by our program)
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segment data use32 class=data
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a db 4Fh
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b dw 8241h
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c resd 1
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; our code starts here
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segment code use32 class=code
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start:
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mov ECX,0
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mov CL,1111_1111b
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mov EAX,0
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mov AL,[a]
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and AL,1111_0000b
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shl EAX,4
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or ECX,EAX
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mov EBX,0
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mov BX,[b]
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and EBX, 0000_0011_1111_1100b
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shl EBX,10
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or ECX,EBX
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mov EAX,0
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mov AL,[a]
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and AL,0000_1111b
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shl EAX,20
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or ECX,EAX
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mov EAX,0
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mov AL,[b+1]
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ror EAX,8
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or ECX,EAX
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mov [c],ECX
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; exit(0)
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push dword 0 ; push the parameter for exit onto the stack
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call [exit] ; call exit to terminate the program
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