The memory in computer

arr.c

#include <stdio.h>

int main()
{
    int a = 3;
    int b = 2;
    int array[3];
    array[0] = 1;
    array[1] = 10;
    array[2] = 100;
    int *pa = &a;
    int i;
    for(i = 0; i < 6; i++) {
        printf("*pa = %d\n", *pa);
        pa++;
    }
    printf("------------------------------------\n");
    pa = &a;
    for(i = 0; i<6; i++) {
        printf("p[%d] = %d\n", i, pa[i]);
    }
}

memory.c

// 0xffffffffffffffff    00000000    |      系统内核        |
// ...                   ...         |                      |
// ----------------------------------------------------------
// 0x7fffffffffffffff    00000000    |                      |
// 0x7ffffffffffffffe    00000000    |         栈           |
// 0x7ffffffffffffffd    00000000    ------------------------
// 0x7ffffffffffffffc    00000000    |                      |
// 0x7ffffffffffffffb    00000000    |    自由可分配内存    |
// 0x7ffffffffffffffa    00000000    |                      |
// 0x7ffffffffffffff9    00000000    ------------------------
// 0x7ffffffffffffff8    00000000    |         堆           |
// 0x7ffffffffffffff7    00000000    ------------------------
// ...                   ...         |                      |      全局变量
// 0x2                   00000000    |       数据段         |   常量、静态变量
// 0x1                   00000000    ------------------------
// 0x0                   00000000    |       代码段         |      p &函数名
// ----------------------------------------------------------

//同一类型变量的声明放在一起（编译器的优化）
//为什么这样会让程序运行更快呢？
//静态变量、局部变量、return

test.c

#include <stdio.h>

int global = 0;

int rect(int a, int b)
{
    static int count = 0;
    count++;
    global++;
    int s = a * b;
    return s;
}

int quadrate(int a)
{
    static int count = 0;
    count++;
    global++;
    int s = rect(a, a);
    return s;
}

int main()
{
    int a = 3;
    int b = 4;
    int *pa = &a;
    int *pb = &b;
    int *pglobal = &global;
    int (*pquadrate)(int a) = &quadrate;
    int s = quadrate(a);
    printf("%d\n", s);
    return 0;
}