B is the set of all binary words: finite$-$length strings of $0$s and $1$s$,$ like $0111$ or $11$ or

$10101000.$ Is B countable? Why or why not? S is the set of all binary sequences: like $0,1,0,1,...$ or $1,0,1,0,0,1,0,0,0,...$ or

$1,1,1,1,....$ Is S countable? Why or why not?