Int 16h is used to access keycode information in the keyboard buffer. Each keycode is stored in the buffer as a two-byte pair by the Int 09h (IRQ1 ISR - PC Keyboard) Interrupt Service. Normally, one byte of the keycode is the scancode for the character and the other byte is the equivalent ASCII character code. When key information is desired, the operating system or an application calls Int 16h, which reads the scancode and character code from the buffer and returns them. The scancode is returned in AH; the ASCII character code is returned in AL.