INT 10h,  13h (19)       Write Character String                          many

    Writes a string of characters with specified attributes to any display
    page.

       On entry:      AH         13h
                      AL         Subservice (0-3)
                      BH         Display page number
                      BL         Attribute (Subservices 0 and 1)
                      CX         Length of string
                      DH         Row position where string is to be written
                      DL         Column position where string is to be written
                      ES:BP      Pointer to string to write

       Returns:       None

       Registers destroyed:      AX, SP, BP, SI, DI

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       Notes:         This service is available only for XTs dated 1/19/86
                      and later, ATs, EGAs, and PC Convertibles.

                      The service has four subservices, as follows:

                      AL=00h: Assign all characters the attribute in BL;
                      do not update cursor
                      AL=01h: Assign all characters the attribute in BL;
                      update cursor
                      AL=02h: Use attributes in string; do not update
                      cursor
                      AL=03h: Use attributes in string; update cursor

                      In Subservices 0 and 1, all characters in the string
                      are written to the screen with the same attribute--
                      the attribute specified in BL.

                      In Subservices 2 and 3, the attribute byte for each
                      character is found in the string itself. The string
                      itself consists of a character followed by its
                      attribute, another character followed by its
                      attribute, and so on. The string is copied directly
                      to the video buffer as is.

                      In Subservices 0 and 2, the cursor position is not
                      updated after the string is written.

                      In Subservices 1 and 3, the cursor is moved to the
                      first position following the last character in the
                      string.

                      Like Service 0Eh, Service 13h responds appropriately
                      to ASCII 07h (bell), 08h (backspace), 10h (line
                      feed), and 0Dh (carriage return). All other
                      characters are printed.