Terminate but Stay Resident (TSR) Program of screen saver (Assembly x86)
code segment assume cs:code main : jmp init mes db “This is screen saver$” old_time dd ? old_kbd dd ? buff db 4000 dup(0) cnt db 0 flag db 0 our_time: push ax push bx push cx push dx push es push ds push ss push si push di mov ax,cs mov ds,ax cmp flag,1 je exit_time inc cnt cmp cnt,100 jne exit_time mov flag,01 mov si,0b800h mov es,si mov cx,2000 lea di,buff mov si,0 save: mov al,es:[si] mov [di],al mov al,’ ‘ mov es:[si],al inc si inc di mov al,es:[si] mov [di],al mov al,00100111b mov es:[si],al inc si inc di dec cx jnz save lea di,mes mov si,2000 print_mes: mov al,[di] cmp al,’$’ je exit_time mov es:[si],al inc di add si,2 jmp print_mes exit_time: pop di pop si pop ss pop ds pop es pop dx pop cx pop bx pop ax jmp cs:old_time our_kbd: push ax push bx push cx push dx push es push ds push ss push si push di mov ax,cs mov ds,ax mov cnt,0 cmp flag,0 je exit_kbd mov flag,0 mov si,0b800h mov es,si mov si,0 mov cx,4000 lea di,buff restore: mov al,[di] mov es:[si],al inc si inc di dec cx jnz restore exit_kbd: pop di pop si pop ss pop ds pop es pop dx pop cx pop bx pop ax jmp cs:old_kbd init: mov ax,cs mov ds,ax cli mov ah,35h mov al,8 int 21h mov word ptr old_time,bx mov word ptr old_time+2,es mov ah,25h mov al,8 lea dx,our_time int 21h mov ah,35h mov al,9 int 21h mov word ptr old_kbd,bx mov word ptr old_kbd+2,es mov ah,25h mov al,9 lea dx,our_kbd int 21h mov ah,31h mov al,0 lea dx,init int 21h sti code ends end main