程序代码：

void hex_n (char *hex)     //传入一个十六进制数，将其转换成二进制，我的方法太笨了吧，有没有简单点的。。。

{
//    char  hex_bin_table[][4] = {"0000","0001","0010","0011","0100","0101","0110","0111","1000","1001","1010","1011","1100","1101","1110","1111"};

    int len_hex = strlen(hex);
//    int flag = 0;

    while (len_hex)
        {
            switch (*hex)

                {
                    case '0':
                        printf ("0000 ");
                        break;
                    case '1':
                        printf ("0001 ");
                        break;
                    case '2':
                        printf ("0010 ");
                        break;
                    case '3':
                        printf ("0011 ");
                        break;
                    case '4':
                        printf ("0100 ");
                        break;
                    case '5':
                        printf ("0101 ");
                        break;
                    case '6':
                        printf ("0110 ");
                        break;
                    case '7':
                        printf ("0111 ");
                        break;
                    case '8':
                        printf ("1000 ");
                        break;
                    case '9':
                        printf ("1001 ");
                        break;
                    case 'a':
                    case 'A':
                        printf ("1010 ");
                        break;
                    case 'b':
                    case 'B':
                        printf ("1011 ");
                        break;
                    case 'c':
                    case 'C':
                        printf ("1100 ");
                        break;
                    case 'd':
                    case 'D':
                        printf ("1101 ");
                        break;
                    case 'e':
                    case 'E':
                        printf ("1110 ");
                        break;
                    case 'f':
                    case 'F':
                        printf ("1111 ");
                        break;
                    default:
                        break;
                }

            len_hex--;
            hex++;

        }

}