新建VI（test3\login_reading.vi），运用循环事件结构，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。(New VI (test3\login_reading.vi), using the loop event structure, login by entering the user name and password, to achieve the correct and wrong input
Before the login, disable and read the button, login, enable the read button, read and display the contents of the text file, encrypt the program block diagram, check the operation.)