sbHTML.Append(“<input type=’text’ name=’txtNum1’ value=”’+x.ToString()+”’/>+<input type=’text’ name=’txtNum2’ value=’’’+y.ToString()+’’’/>=<input type=’text’ name=’txtSum’ value=’’’+z.ToString()+’’’/><br/>”);
问题：程序中value=”’+x.ToString()+”、   value=’’’+y.ToString()+’’’  、value=’’’+z.ToString()+’’’用来起什么作用的？

给input标签的value属性赋值