程序代码：

/*

 * 实现一个小孩随便跑程序

 * 设计效果 :

 *     小孩用*打印，假设界面是30 * 30的数组矩阵。程序开始时，小孩的位置随机

 * 产生，w / W(上)s / S(下)a / A(左)d / D(右)控制小孩的移动方向，每击键(wsad)

 * 一次按一下回车键，小孩向对应方向移动1下(1字符)。当跑出边缘，则小孩会从相反方

 * 向的边缘进入界面，因而小孩由始至终都在界面上乱跑。按下q / Q键退出，程序结束。

 */

#include <time.h>
#include <stdio.h>
#include <conio.h>
#include <windows.h>

#define GRAPH_SIZE   20

void Init();
void gotoXY(int, int);

int  X, Y;

int main()
{
    char ch;

    Init();
    while (1)
    {
        gotoXY(X, Y);
        putchar(0xa3), putchar('*' + 0x80);

        while (!_kbhit());

        gotoXY(X, Y);
        putchar(' '), putchar(' ');

        ch = _getch();
        if ('q' == ch)
        {
            break;
        }
        switch (ch)
        {
        case 'a':
            X = (X + GRAPH_SIZE - 2) % GRAPH_SIZE + 1;
            break;
        case 's':
            Y = Y % GRAPH_SIZE + 1;
            break;
        case 'd':
            X = X % GRAPH_SIZE + 1;
            break;
        case 'w':
            Y = (Y + GRAPH_SIZE - 2) % GRAPH_SIZE + 1;
            break;
        default:    break;
        }
    }

    return 0;
}

void Init()
{
    int i;
    CONSOLE_CURSOR_INFO cursor_info;

    //光标不显示
    cursor_info.bVisible = FALSE;
    cursor_info.dwSize   = 20;
    SetConsoleCursorInfo(GetStdHandle(STD_OUTPUT_HANDLE), &cursor_info);

    //画界面
    for (i = 0; i <= GRAPH_SIZE + 1; i++)
    {
        printf("%s", "█");
    }
    for (i = 1; i <= GRAPH_SIZE; i++)
    {
        gotoXY(0, i), puts("█");
        gotoXY(GRAPH_SIZE + 1, i), puts("█");
    }
    for (i = 0; i <= GRAPH_SIZE + 1; i++)
    {
        printf("%s", "█");
    }

    //小孩位置初始化
    srand(time(NULL));
    X = rand() % GRAPH_SIZE;
    Y = rand() % GRAPH_SIZE;
}

void gotoXY(int x, int y)
{
    COORD coord = { 2 * x, y };
    SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE), coord);
}