add more in pointer

01.Basic/Pointer.cpp

@@ -6,20 +6,75 @@ int main() {
 
     string food = "Pizza"; // A food variable of type string
 
-    cout << "Output value and address by variable and reference" << endl;
+    cout << "----- Output value and address by variable and reference -----" << endl;
     cout << food << endl;  // Outputs the value of food (Pizza)
     cout << &food << endl; // Outputs the memory address of food (0x6dfed4)
 
     // 定义指针
-    cout << "Output value and address by pointer" << endl;
+    cout << "----- Output value and address by pointer -----" << endl;
     string* ptr = &food;
     cout << *ptr << endl;
     cout << ptr << endl;
 
     // 修改指针指向内存的值
-    cout << "Modify value by pointer" << endl;
+    cout << "----- Modify value by pointer -----" << endl;
     *ptr = "Hamburger";
     // 指针指向变量的值也被改变了
     cout << food << endl;
     
+    // 数组和指针
+    // number是指向数组第一个成员的指针，但是number不可移动
+    int number[3] = {10, 100, 200};
+    // 在大多数的操作系统上，程序不允许访问地址为 0 的内存，因为该内存是操作系统保留的。
+    // 然而，内存地址 0 有特别重要的意义，它表明该指针不指向一个可访问的内存位置。
+    // 但按照惯例，如果指针包含空值（零值），则假定它不指向任何东西。
+    int * ptrNumber = NULL;
+
+    // 将指针指向数组的第一个成员
+    ptrNumber = number;
+    // 下面这句会报错，数组number是不可移动的指针
+    // number = ptrNumber;
+    // 循环数组，如果指针未超过最后一个成员，打印数组成员的值
+    cout << "----- Loop array by single pointer -----" << endl;
+    while (ptrNumber <= &number[2]) {
+
+        cout << "Element value = [" << *ptrNumber;
+        cout << "]; address = [" << ptrNumber << "]" << endl;
+        ptrNumber++; // 指针移动到下一个成员
+
+    }
+
+    // 也可以定义指针数组，数组的所有成员都是指针类型
+    cout << "----- Loop array by pointer array -----" << endl;
+    int * ptrArray[3] = {NULL, NULL, NULL};
+
+    // 将指针数组的成员的值，设定为number成员的地址
+    for (int i = 0; i < 3; i++) {
+
+        ptrArray[i] = &number[i];
+
+    }
+
+    // 循环指针数组，打印每个成员指向的地址的值
+    for (int i = 0; i < 3; i++) {
+
+        cout << "Element value = [" << *ptrArray[i];
+        cout << "]; address = [" << ptrArray[i] << "]" << endl;
+
+    }
+
+    // 指向指针的指针
+    int var;
+    int *ptrVar;
+    int **pptrVar;
+
+    var = 3000;
+    ptrVar = &var;      // ptrVar的值，是var的地址
+    pptrVar = &ptrVar;  // pptrVar的值，是ptrVar的地址
+
+    cout << "----- Pointer to pointer -----" << endl;
+    cout << "Value[var] = [" << var << "]; address = " << &var << endl;
+    cout << "Value[ptrVar] = [" << ptrVar << "]; address = " << &ptrVar << endl;
+    cout << "Value[pptrVar] = [" << pptrVar << "]; address = " << &pptrVar << endl;
+
 }
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