diff --git a/practical_exercises/10_day_practice/day7/一元运算符/计数器前后自增.cpp b/practical_exercises/10_day_practice/day7/一元运算符/计数器前后自增.cpp
index 90d94f8..d85d885 100644
--- a/practical_exercises/10_day_practice/day7/一元运算符/计数器前后自增.cpp
+++ b/practical_exercises/10_day_practice/day7/一元运算符/计数器前后自增.cpp
@@ -1,4 +1,4 @@
-//���һ��������counter�������Ա�������������ʵ�ּ�����������������Ԫ����ʵ�ּ��������Լ���
+//设计一个计数器counter，用类成员重载自增运算符实现计数器的自增，用友元重载实现计数器的自减。
 #include<iostream>
 using namespace std;
 class Counter{
@@ -17,16 +17,18 @@ Counter Counter::operator++(){
     return *this;
 }
 Counter Counter::operator++(int){
+    Counter t=*this;
     n++;
-    return *this;
+    return t;
 }
 Counter operator--(Counter &c){
     --c.n;
     return c;
 }
 Counter operator--(Counter &c,int){
+    Counter t=*this;
     c.n--;
-    return c;
+    return t;
 }
 void Counter::display(){
     cout<<"counter number="<<n<<endl;