Typically, ALSA supports up to eight "cards", numbered 0 through 7; each card is a physical or logical kernel device capable of input, output, or, and card number 0 is used by default when no particular card is specified.
ALSA supports up to eight "cards". This was typically. Eight is numbered 0 through 7. Each card is a physical or logical kernel device capable of input. Input is output. Card number 0 is used by default. No particular card is specified.