学步园

按键                          i                         buffer                           read

abc123+ET            0                        97                                 代码停在此，等待输入 触发代码运行    

d+ET                       0                                                              100

                                1                        98 （先执行）             13 （后执行 根据代码顺序）                         

                                2                         99                                  10

                               3                          49                                  代码停在此，等待输入 触发代码运行    

d+ET                      3                                                               100  输入后触发运行

                               4                          50                                  13

                               5                          51                                  10

                               6                          13                                    代码停在此，等待输入 触发代码运行    

d+ET                    6                                                                   100   

                              7                           10                                  13