Data storage method
After the program is written, it needs to be loaded into the computer's core or semiconductor memory before it can run. Computer programs are organized into 4 logical segments: executable code, static data, dynamic data (heap) or stack.
executable code and static data are stored in fixed memory locations;
Dynamic data requires the system to dynamically allocate memory, which is generally stored in the memory pool of the heap area;
Local data objects, function parameters, and the relationship between the calling function and the called function are stored in the memory pool in the stack area.
堆：程序可动态分配和释放内存的自由存储空间叫栈；
int *p=(int *)malloc(20); //分配内存
free(p);// 回收内存
栈：是一个后进先出的数据结构，当向栈中压入一个对象，则指针向下移动一个位置；
当系统弹出栈顶元素时，指针向上移动一个位置。
#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
int main()
{
int *p=(int *)malloc(20); //分配内存
free(p);// 回收内存
int *p=(int *)calloc(2, 20);//在内存中动态分配2个长度为20的连续内存空间
//将p指针指向的内存空间大小改为30
realloc(p, 30);
return 0;
}