Tetris preliminary

The following code can show the whereabouts of two blocks .

#include <iostream>
#include <stdio.h>
#include <unistd.h>
#include <conio.h>
using namespace std;
//Tetris
class point
{
    
private:
    int (*a)[10];
public:
    point()
    {
    }
    void at(int (*a)[10])
    {
    
        this->a=a;
    }
    void move(int& k,int &t)
    {
    
        if(k==0)
        {
    
            a[k][0]=0; // The first box turns black at the beginning 
            a[k+1][0]=0;// The second space turns black at the beginning 
        }
        if(k!=0 && k<20)
        {
    
            a[t][0]=1;  // The previous box becomes blank 
            a[k][0]=0;  // Current grid turns black 
            a[k+1][0]=0;// The next box turns black 
        }
    }
};
class cdown
{
    
private:
    point m_p;
public:
    cdown(int (*a)[10])
    {
    
        m_p.at(a);
    }
    void begin(int& k,int &t)
    {
    
        m_p.move(k,t);
    }
    void end(int& k,int& t)
    {
    
        if(k<20)
        {
    
            printf("%d\n",k);
            t=k;
            k=k+1;
        }
    }
    void shape(int& k,int& t)
    {
    

    }
    ~cdown()
    {
    }
};
int main(int argc, char** argv)
{
    
    int  i=0;
    int  j=0;
    int  k=0;
    int  t=0;
    int a[20][10];
    for(i=0; i<20; i++)
    {
    
        for(int j=0; j<10; j++)
        {
    
            a[i][j]=1;
        }
    }
    cdown down((a));
    while(1)
    {
    
        down.begin(k,t);
        for(i=0; i<20; i++)
        {
    
            for(j=0; j<10; j++)
            {
    
                if(a[i][j]==0)
                {
    
                    printf("■");
                }
                else
                {
    
                    printf("□");
                }
            }
            printf("\n");
        }
        down.end(k,t);
        sleep(1);
        clrscr();
    }
    return 0;
}