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C++程序在执行时,将内存大方向划分为4个区域
内存四区意义:
不同区域存放的数据,赋予不同的生命周期, 给我们更大的灵活编程
一、代码运行前
在程序编译后,生成了exe可执行程序,未执行该程序前分为两个区域
代码区:只读、存放执行指令、可共享;
全局区:执行结束后会释放该空间;
代码示例:(注:地址是int*类型,强制转换int会报错)
#include#include #include using namespace std;//全局变量int g_a = 10;int g_b = 10;//全局常量const int c_g_a = 10;const int c_g_b = 10;int main() { //局部变量 int a = 10; int b = 10; //打印地址 cout << "局部变量a地址为: " << &a << endl; cout << "局部变量b地址为: " << &b << endl; cout << "全局变量g_a地址为: " << &g_a << endl; cout << "全局变量g_b地址为: " << &g_b << endl; //静态变量 static int s_a = 10; static int s_b = 10; cout << "静态变量s_a地址为: " << &s_a << endl; cout << "静态变量s_b地址为: " << &s_b << endl; cout << "字符串常量地址为: " << &"hello world" << endl; cout << "字符串常量地址为: " << &"hello world1" << endl; cout << "全局常量c_g_a地址为: " << &c_g_a << endl; cout << "全局常量c_g_b地址为: " << &c_g_b << endl; const int c_l_a = 10; const int c_l_b = 10; cout << "局部常量c_l_a地址为: " << &c_l_a << endl; cout << "局部常量c_l_b地址为: " << &c_l_b << endl; system("pause"); return 0;}
二、程序运行后、new操作(堆区)
栈区:由编译器自动分配释放, 存放函数的参数值,局部变量等
堆区:由程序员分配释放,若程序员不释放,程序结束时由操作系统回收;在C++中主要利用new在堆区开辟内存
#include#include #include using namespace std;//全局变量int g_a = 10;int g_b = 10;//全局常量const int c_g_a = 10;const int c_g_b = 10;int* func(){ int* a = new int(10); //通过new关键字开辟堆区;这里a指向的内存地址,存取的值为10; int* arr = new int[10]; for (int i = 0; i < 10; i++) { arr[i] = i + 100; } //return arr; return a;}int main() { //局部变量 int a = 10; int b = 10; //打印地址 cout << "局部变量a地址为: " << &a << endl; cout << "局部变量b地址为: " << &b << endl; cout << "全局变量g_a地址为: " << &g_a << endl; cout << "全局变量g_b地址为: " << &g_b << endl; //静态变量 static int s_a = 10; static int s_b = 10; cout << "静态变量s_a地址为: " << &s_a << endl; cout << "静态变量s_b地址为: " << &s_b << endl; cout << "字符串常量地址为: " << &"hello world" << endl; cout << "字符串常量地址为: " << &"hello world1" << endl; cout << "全局常量c_g_a地址为: " << &c_g_a << endl; cout << "全局常量c_g_b地址为: " << &c_g_b << endl; const int c_l_a = 10; const int c_l_b = 10; cout << "局部常量c_l_a地址为: " << &c_l_a << endl; cout << "局部常量c_l_b地址为: " << &c_l_b << endl; int *p = func(); cout << *p << endl; cout << *p << endl; //利用delete释放堆区数据,程序员手动释放; delete p; //delete[] p; //如果是数组类型,前面需要加[]; //cout << *p << endl; //报错,释放的空间不可访问 system("pause"); return 0;}
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