说明：  通过输入用户名和密码后登录，实现输入正确和错误提示、登录前禁用并灰显读取按钮、登录后启用读取按钮、读取并显示文本文件内容、加密程序框图查看操作。
(By inputting user name and password and login, we can input correct and error prompts, disable and gray display the reading button before login, enable the reading button after login, read and display the contents of text files, and view the encrypted program block diagram.)