简单的求和工具,在第一个文本框中个输入第一个加数；在第二个文本框中输入第二个加数，单击“=”按钮时在第三个文本框中显示前两数之和-Simple summation tool in the first text box, enter the first addend "=" button is displayed in the second text box, enter the second addend, click the text box in the third the first t