Hola, estoy tratando de entender la INT 10h, 13h (19) que escribe una Cadena de caracteres con la interrupción del BIOS 10 con 13h en ah. He encontrado la información a continuación sobre las diferentes banderas para colocar en los diferentes registros. Una cosa que todavía no entiendo es lo que se supone que debe ir en BL, si simplemente quiero escribir una cadena con esta función, ¿qué debería haber en BL como atributo? En este momento escribe símbolos extraños que no tienen sentido. Gracias de antemano

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

   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.