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SECTION .data       ; data section
msg:    db "Hello World",10 ; the string to print, 10=cr
test:   db "test",10
len:    equ $-msg       ; "$" means "here"
                ; len is a value, not an address

    SECTION .text       ; code section
        global main     ; make label available to linker 
main:               ; standard  gcc  entry point

    mov edx,len     ; arg3, length of string to print
    mov ecx,msg     ; arg2, pointer to string
    mov ebx,1       ; arg1, where to write, screen
    mov eax,4       ; write sysout command to int 80 hex
    int 0x80        ; interrupt 80 hex, call kernel

    mov ebx,0       ; exit code, 0=normal
    mov eax,1       ; exit command to kernel
    int 0x80        ; interrupt 80 hex, call kernel

Beginner question but why do this code print "Hello word test " it was only expected to print msg so hello world"?

I build this way 

nasm -f elf -g test.asm
gcc -m32 -g -o file test.o
1201ProgramAlarm
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  • It prints `len` bytes starting at `msg`. The value of `len` includes the length of both strings, so it prints both strings. – prl May 08 '19 at 19:48
  • OK thanks I should write this way then. msg: db "Hello World",10 ; the string to print, 10=cr len: equ $-msg – user3409988 May 08 '19 at 20:04

0 Answers0