asm problem

vreau prin intermediul BIOS (int 10h) sa asfishez un caracter dar nu merge...adica cand sunt in windows se afisheaza insa cand ma pornesc de pe disketa nu merge...iata codul...asta-i tpa o diketa bootabila.....model tiny.codeorg 100hmain:jmp startmsg db 'Mini OS v0.1'len equ $-msgprompt db 'Cmd: 'prompt_len equ $-promptbuffer db 256 dup(?)start: movax,csmoves,axmovbp,7f03hmovax,1301hmovbh,0hmovbl,0fhmovcx,lenmovdh,0movdl,0int 10hmovax,csmoves,axmovbp,7f0fhmovax,1301hmovbh,0hmovbl,0fhmovcx,prompt_lenmovdh,4movdl,0int 10hmov ah,02hmov bh,0mov dh,6mov dl,10int 10h;ascunde cursorul;mov ax,0100h ;mov cx,2607h ;int 10h ;aratam cursorul mov ax,0100h mov cx,0506h int 10h;==========AICI NU MERGE=========================mov ah,0ahmov al,'G'mov bh,0mov cx,5int 10h;===================================; mai departe nu are rost de uitat....;===================================;mov cx,0;a:;mov ah,00h;int 16h;cmp al,13;je mai_departe;mov [buffer][si],al;mov ah,0eh;int 10h;inc siinc cx;jmp amai_departe: ;mov ah,4Ch;int 21hend mainca atare vreau sa fac un prompter... care sa citeasca comenzi... poate are cineva ideie cum da facut daca nu asha apu cum?10x