VC限制编辑框输入文本的长度，也就是像WEB表单中的输入框功能类似，限制用户输入字符的数量，这样可以预防用户输入了超过规定限制的字符数量，有效避免程序出错。在本例的输入框中，中允许用户输入7个字符，再多的话就无法输入进去了。

-VC limit the length of the input text edit box, which is similar to the input box like WEB form, to limit the number of characters of user input, which can prevent the user to enter the number of characters that exceed the specified limits, effectively avoid procedural errors. In this example, the input box allows the user to enter seven characters, no amount of words can not enter into it.