用S3CEV40试验箱上小键盘和超级终端，设计一个简易密码键盘，键盘布局如图所示，

要求：

1. 输入密码时，只显示“*”，

2. 密码位数为6位，超过六位后，不再显示，但输入有效

3. 按下“确认”键后（该键位不显示），与预留密码进行比较

4. 比较正确，显示“OK！”，否则显示“Error！”

5. 连续三次错误后，锁定键盘

-S3CEV40 chamber with the keypad and super terminal, designed a simple password keyboard, the keyboard layout as shown,

Claim:

1 When you enter a password, only the "*",

2 to 6 digit password, after more than six, no longer displayed, but enter a valid

3 Press the "OK" button (the keys are not displayed), and the password is compared reserved

4 more accurate display "OK!", Otherwise it displays "Error!"

5 After three consecutive errors, lock the keypad