diff --git a/src/java2020spring/BaseCalculator.java b/src/java2020spring/BaseCalculator.java
new file mode 100644
index 0000000000000000000000000000000000000000..f8d3b582e17f4a9b69e617888c6a5dc01473c412
--- /dev/null
+++ b/src/java2020spring/BaseCalculator.java
@@ -0,0 +1,285 @@
+package java2020spring;
+
+import java.awt.*;
+import java.awt.event.*;
+import java.util.Stack;
+import javax.swing.*;
+
+public class BaseCalculator extends JFrame implements ActionListener{
+	
+	StringBuilder secondNum = new StringBuilder();        //存储运算符之后的数字
+	
+	double result = 0;                      
+	
+	double num = 0;
+	
+	int count = 0;                                           //统计运算符的个数
+	
+	char oper = ' ';                                         //用于对每个运算符做相应的标识
+	
+	boolean M = false;                                       //用于记录是否按下“M+”或“M-"
+	
+	double saveResult = 0;                                   //用于记录通过按下“M+”或“M-”存储的数字
+	
+	JTextField showArea;
+	
+	JButton [] button = new JButton[28];
+	
+	Stack<Double> numStack = new Stack<Double>();      //声明一个栈用于存储数字
+	
+	Stack<Double> saveNum =new Stack<Double>();        //声明一个栈用于通过按下“M+”或“M-”存储的数字
+	//计算器上的按钮的字符
+	String [] symbol = {"MC","MR","M+","M-",
+			            "%","CE","C","Del",
+                        "1/x","x²","√x","÷",
+                        "7","8","9","×",
+                        "4","5","6","-",
+                        "1","2","3","+",
+                        "±","0",".","="};
+	
+	JPanel p;
+	
+	public BaseCalculator() {
+		init();
+		setTitle("标准计算器");
+		setBounds(100,100,300,400);
+		setVisible(true);
+		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+	}
+	
+	void init() {
+		showArea = new JTextField();
+		showArea.setHorizontalAlignment(JTextField.RIGHT);          //将文本框的光标置于右边
+		showArea.setFont(new Font("Arial",Font.BOLD,18));
+		showArea.setPreferredSize(new Dimension(300,60));           //将文本框设置成合适大小
+		add(showArea,BorderLayout.NORTH);
+		p = new JPanel();
+		p.setLayout(new GridLayout(7,4));       //将p的布局设置为7行4列的GridLayout布局以便存放按钮
+		//利用循环逐一设置每个按钮并注册监视器
+		for(int i=0;i<28;i++) {
+			button[i] = new JButton(symbol[i]);
+			button[i].addActionListener(this);
+			button[i].setFont(new Font("Arial",Font.BOLD,18));
+			p.add(button[i]);
+		}
+		add(p);
+	}
+	
+	public void actionPerformed(ActionEvent e) {
+		String text=e.getActionCommand();        //记录按钮上的命令字符
+		//按下“CE”按钮时
+		if(text.equals("CE")) {
+			//若缓冲区有数字则将要其清空
+			if (secondNum.length() > 0) {
+				secondNum.delete(0, secondNum.length());
+			}
+			showArea.setText("");                 //同时将当前文本框清空
+		}
+		//按下“C”按钮时，将一切恢复至初始状态
+		if(text.equals("C")) {
+			if (secondNum.length() > 0) {
+				secondNum.delete(0, secondNum.length());
+			}
+			showArea.setText("");
+			count=0;
+			//清空栈内的数字
+			while(!numStack.isEmpty()) {
+				numStack.pop();
+			}
+		}
+		//按下“1/x”按钮时
+		if(text.equals("1/x")) {
+			num=Double.parseDouble(showArea.getText());    //将文本框内的字符串转化成浮点数
+			//满足“分母不能为0”的条件
+		    if(num!=0) {                                   
+				num=1/num;
+				showArea.setText(String.valueOf(num));
+			}
+			else {
+				showArea.setText("");
+			}
+		}
+		//按下“x²”按钮时
+		if(text.equals("x²")) {
+			num = Double.parseDouble(showArea.getText());
+			num*=num;
+			showArea.setText(String.valueOf(num));
+		}
+		//按下“√x”按钮时
+		if(text.equals("√x")) {
+			if(num>=0) {
+				num = Double.parseDouble(showArea.getText());
+				num = Math.sqrt(num);
+				showArea.setText(String.valueOf(num));
+			}
+			else
+				showArea.setText("");
+		}
+		//按下“±”按钮时
+		if(text.equals("±")) {
+			num = Double.parseDouble(showArea.getText());
+			num*=(-1);
+			showArea.setText(String.valueOf(num));	
+		}
+		//按下“%”按钮时
+		if(text.equals("%")) {
+			num = Double.parseDouble(showArea.getText());
+			num*=0.01;
+			showArea.setText(String.valueOf(num));
+		}
+		//按下“Del”按钮时，即是退格
+		if(text.equals("Del")) {
+			int length = showArea.getText().length();
+			if(length==1) {
+				showArea.setText("");
+				if (secondNum.length() > 0) {
+					secondNum.delete(0, secondNum.length());
+				}
+			}
+			else {
+				showArea.setText(showArea.getText().substring(0,length-1));
+				if(secondNum.length()>0) {
+					secondNum.delete(secondNum.length()-1,secondNum.length());
+				}
+			}
+		}
+		//按下“.”按钮时
+		if(text.equals(".")) {
+			if(showArea.getText().equals("")||showArea.getText().equals("0")) {
+				showArea.setText("0.");
+			}
+			else if(showArea.getText().indexOf(".")==-1) {
+				showArea.setText(showArea.getText()+".");
+				secondNum.append(text);
+			}
+		}
+		//按下数字按钮时
+		if(text.matches("[0-9]")) {
+			// 判断是否为第一个数
+			if(numStack.isEmpty()) {
+				showArea.setText(showArea.getText()+text);
+			}
+			// 如果是运算符之后的数字
+			else {
+				// 先将该数字添加到缓冲区
+				secondNum.append(text);
+				// 再写入文本框
+				showArea.setText(secondNum.toString());
+			}
+	    }
+		//按下运算符按钮时
+		String regex="[\\+\\-\\×\\÷]";
+		if(text.matches(regex)) {
+			// 按下运算符时清空缓存区，方便继续存储按下运算符之后的数字
+			if (secondNum.length() > 0) {
+				secondNum.delete(0, secondNum.length());
+			}
+			//如果是第一次按下运算符键
+			if(numStack.isEmpty() && count == 0) {
+				num=Double.parseDouble(showArea.getText());
+				numStack.push(num);             //将输入的第一个数字先压入栈内
+			}
+			//按下“+”按钮时
+			if(text.equals("+")) {
+				count++;                        //每一次按下运算符都会进行计数
+				 //当按下运算符的次数多于等于2次时，总先将此运算符前的两个数做运算
+				if(count>=2) {                 
+					calculate();
+				    numStack.push(result);
+				    showArea.setText(String.valueOf(result));
+				}
+				//对此运算符做标记，若在这之后再按运算符即可做出相应的运算
+				oper='+';                         
+			}
+			//按下“-”按钮时
+			if(text.equals("-")) {
+				count++;
+				if(count>=2) {
+					calculate();
+					numStack.push(result);
+					showArea.setText(String.valueOf(result));
+				}
+				oper='-';
+			}
+			//按下“×”按钮时
+			if(text.equals("×")) {
+				count++;
+				if(count>=2) {
+					calculate();
+					numStack.push(result);
+					showArea.setText(String.valueOf(result));
+				}
+				oper='*';
+			}
+			//按下“÷"按钮时
+			if(text.equals("÷")) {
+				count++;
+				if(count>=2) {
+					calculate();
+					numStack.push(result);
+					showArea.setText(String.valueOf(result));
+				}
+				oper='/';
+			}
+		}
+		//按下“=”按钮时
+		if(text.equals("=")){
+			calculate();          //计算最后两个数
+			count = 0;            //并将按下运算符的次数清空
+			oper=' ';             
+			showArea.setText(String.valueOf(result));
+		}
+		//MC或MR事件的执行必须建立在用户按下了M+或M-按钮的前提下
+		//按下“MC”按钮时，将存储起来的栈清空，并将一切初始化
+		if(text.equals("MC")&&M) {
+			while(!saveNum.isEmpty()) {
+				saveNum.pop();
+			}
+			M = false;
+			saveResult = 0;	
+		}
+		//按下“MR”按钮时
+		if(text.equals("MR")&&M) {
+			saveResult = saveNum.pop();
+			showArea.setText(String.valueOf(saveResult));
+		}
+		//按下“M+”按钮时
+		if(text.equals("M+")) {
+			num = Double.parseDouble(showArea.getText());
+			if(saveNum.isEmpty()){
+				saveNum.push(num);		
+			}
+			else{
+				saveResult = num + saveNum.pop();
+				saveNum.push(saveResult);
+			}
+			M = true;
+		}
+		//按下“M-”按钮时
+		if(text.equals("M-")) {
+			num = Double.parseDouble(showArea.getText());
+			if(saveNum.isEmpty()){
+				saveResult = (-1) * num;
+				saveNum.push(saveResult);		
+			}
+			else{
+				saveResult = saveNum.pop() - num;
+				saveNum.push(saveResult);
+			}
+			M = true;
+		}
+	}
+	//对已标记的运算符做相应的运算
+	public double calculate() {
+		num=Double.parseDouble(showArea.getText());
+		if(oper=='+')
+			result = numStack.pop() + num; 
+		else if(oper=='-')
+			result = numStack.pop() - num; 
+		else if(oper=='*')
+			result = numStack.pop() * num; 
+		else if(oper=='/')
+			result = numStack.pop() / num; 
+		return result;
+	}
+}
diff --git a/src/java2020spring/StartUp.java b/src/java2020spring/StartUp.java
new file mode 100644
index 0000000000000000000000000000000000000000..530ed4b756ebe901b5a11dfa7fa686ada9743379
--- /dev/null
+++ b/src/java2020spring/StartUp.java
@@ -0,0 +1,8 @@
+package java2020spring;
+
+public class StartUp {
+	public static void main(String args[]) {
+		BaseCalculator calculator=new BaseCalculator();
+	}
+
+}