INT 10h,  0Fh (15)       Get Current Video Mode

    Reports the current video mode, the number of character positions per
    line in that video mode, and the current display page.

       On entry:      AH         0Fh

       Returns:       AL         Video mode
                      AH         Number of character columns per line
                      BH         Active display page number

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

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       Notes:         See Service 00h for a table of the video modes and
                      how to set the current video mode.