Electronic time clock display system, and use the way of rewriting int 9 interrupt "during the time display can enter any characters, display on the screen", rewrite the int 9 interrupt code is as follows:
Int9:
Push ax
Push bx
Push dx
In al, 60 h
Pushf
Pushf
Pop bx
And bh, 11111100 b
Push bx
Popf
Call dword PTR ds: [0]

CMP al, 01 h; The esc key scan code
Developed int9ret

; Restore the interrupt vector
Mov ax, 0
Mov es, ax

Push ds: [0]
Pop es: [9 * 4)
Push ds: [2]
Pop es: [9 * 4 + 2]

Mov ax, 4 c00h
Int 21 h

Int9ret:
mov ah, 01 h
Int 16 h
Pushf; Detect the presence of keyboard input
Pop bx
And bl, 01000000 b
CMP bl, 01000000 b
Je over; No keyboard input

Mov ah, 00 h; Have a keyboard input is read ASCII
Int 16 h
Mov dl, al; Displayed on the screen
Mov ah, 02 h
Int 21 h

Over: pop dx
Pop bx
Pop ax
Iret
Why do you want to add the red font part, not trigger int 9 interrupt means has a keyboard input??