初学者 请帮注释下个别地方

    #include"at89x51.h"
   
    unsigned int j;
    unsigned char i,k,cz;
    unsigned char a[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f,0x00,0x7c};
    unsigned char b[]={0,0,0,0};
    unsigned char wx=100;
    csh()
    {
     IE=0x85;  //EA=1;EX1=1;EX0=1;
     TCON=0x05;//IT0=1;IT1=1;*/
    }

    bcd()
    {      b[0]=10;
        b[1]=wx/100;
        b[2]=(wx%100)/10;
        b[3]=wx%10;
    }
 
    tv()                                从这里到
    {   
       cz=0xfe;  
       for(i=0;i<4;i++)        
          {
        k=b[i];
                P2=a[k];
            P0=cz;   
            for(j=0;j<550;j++);
          cz=(cz<<1)+1;                    这里   主要是这个tv函数有些不懂

         }
     }

void main(void)
{    csh();
    while(1)
           {
        bcd();
        tv();
           }
}

KINT0() interrupt  0
   {wx=wx+1;
    if(wx>=120){wx=120;}
   }

KINT1() interrupt  2
   {wx=wx-1;
    if(wx<80)wx=80;
   }