字符串 Output 在实模式下使用 LODS 指令

Question

I'm need to write function, which output a string in real-mode. There is that code:

;; ds:si - string address, cx - length of string
   cld
putc:
   lods
   mov ah, 0x0E
   xor bh, bh    
   int 0x10          ;; display character, advancing cursor and scrolling screen
                     ;; as necessary
   loop putc

But it output only first character few (defined by the CX register) times, ae the SI register don't increase. Is where a error?

Answer 1

lods isn't a valid instruction mnemonic; you probably mean lodsb .

On my assembler (nasm), a token that isn't a valid mnemonic gets parsed as a label instead, and so no code is emitted. Thus your lods is effectively a no-op, so no wonder SI doesn't increment. (The assembler does give a warning though, does yours?)