INT DD - STSC APL*PLUS/PC v9.0 - PLACE KEYSTROKE EVENTS IN INPUT BUFFER
        BX = where to place keystrokes
            FFFFh insert before current buffer contents
            0000h replace current contents
            0001h insert after current contents
        CX = number of keystroke events to insert
        ES:SI -> data to be placed into buffer (list of WORD key codes)
            4000h + N = normal ASCII keystroke N (N = 00h to FFh)
            4100h + N = extended ASCII keystroke N (N = 03h to 84h)