c++ - strcmp和==的区别?

Example:

    char alpha;
    scanf("%c", &alpha);
    if (strcmp(&alpha, "c") == 0) //if (alpha == 'c')
    {
        printf("same");
    }
    else
    {
        printf("different");
    }

man page上的 description也没有讲具体

The strcmp() function compares the two strings s1 and s2. It returns an integer less than, equal to, or greater than zero if s1 is found, respectively, to be less than, to match, or be greater than s2.

我谷歌了, 但只找到了http://stackoverflow.com/ques... , c 部分感觉不是很详细, 想在这里请教下大家这两者实现机制的区别与效率