; D_name point" />
dirp->; D_name is a character pointer. If there is "abc.mp3" now,
dirp->; D_name points to' a', dirp->; D_name+ 1 points to' b' ..., then size=strlen("abc.mp3")=7,
dirp->; d _ name+(7-4)= dirp-& gt; d_name+3,dirp-& gt; D_name+3 points to ".",
dirp->; D_name+3 points to the string ".mp3". Then compare it with the constant string ".mp3", and if it is different, execute the next loop.