emu8086无法在模拟器屏幕上打印数字

Question

i'm trying to display the result of multiplying two numbers on the emulator screen of emu8086, when i use small 8 bits numbers, the result is printed fine when i run the code, but with 16bits numbers i get 0 on the emulator screen, i'm not sure it something is wrong with my code or the emulator it self, i'm totally new to assembly, and i've been trying to solve it for the past hour, that's my code

    include 'emu8086.inc' 
    name "multiply_two_16_bit_numbers"

    org 100h

    mov ax, 512   ; 
    mov bx, 512   ;

    mul bx 

    call print_num

    ret
    DEFINE_PRINT_NUM
    DEFINE_PRINT_NUM_UNS
    end

hope you guys could help me please, thanks.

Answer 1

Note that 512*512=262144=40000h, which is a 32 bit number with the low 16 bits being zero and that's presumably what you get printed. This form of the mul instruction puts the top 16 bits of the result into register dx , you should find 4 there. If you want to print the whole result, you will of course need a 32 bit printing function, and you'll have to pass the arguments properly.