#include <stdio.h>
#include <stdlib.h>
#include <Windows.h>
#include <time.h>
void closeQQ();
void go();
void openQQ();
int x[13];
int y[7];
void main()
{
    go();
    openQQ();
    Sleep(1000);
    closeQQ();
}
void openQQ()
{
    system("\"D:\\Program Files (x86)\\Tencent\\QQ\\Bin\\QQScLauncher.exe\"");
}
void closeQQ()
{
    system("taskkill /f /im QQ.exe");
}
void go()
{
    HWND QQwin = FindWindowA("TXGuiFoundation", "QQ");
    if (QQwin == NULL)
    {
        MessageBox(QQwin, "没有找到窗口", "Windows", 0);
    }
    time_t ts;
    unsigned int num = time(&ts);
    srand(num);
    for (int i = 0; i <= 20; i++)
    {
        x[i] = rand() % 14;
        y[i] = rand() % 8;
    }
    for (int n = 0; n <= 20; n++)
    {
        SetWindowPos(QQwin, NULL, x[i],y[i], 500, 600, 0);
    }
    getchar();
}

    3    IntelliSense:  未定义标识符 "i"    d:\程序\Project1\Project1\软件开发.c    42    31    软件开发

       错误    2    error C2059: 语法错误:“]”    d:\程序\project1\project1\软件开发.c    42    1    软件开发

int i;   /*i在这里定义*/
for(i = 0; i <= 20; i++)

你的编译器不支持在for循环里面定义，把int i;放在for前面定义