四位数码管接显示数据后，之后自动清零，最后一位又不显示

Question

#include<reg51.h>
#define uint unsigned int
#define uchar unsigned char
sbit K1=P3^0;
sbit K2=P3^2;
void display();
uint count=0,flag,BJ=3,n,k;
uchar code wei[]={0x01,0x02,0x04,0x08};
uchar code duan[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f};
uchar data a[]={0,0,0,0};
double u;
void delay(uint t)
{
    uint i,j;
    for(i=t;i>0;i--)
    for(j=110;j>0;j--);
}
void main()
{
    IE=0X83;
    TMOD=0X01;
    TH0=(65536-50000)/256;
    TL0=(65536-50000)%256;
    while(1)
    {
    if(K1==0)
    {
        while(K1==0)
        {
            TR0=1;
            flag=0;           //正常
        }
    }
    }
}
void INIT()interrupt 0
{
    if(K2==0)
    {
        TR0=0;
        while(K2==0)
        {
            u=50*count/1000;
            count=0;
            if(u<BJ)
            {
                flag=0;
                display();
            }
            else if(u>BJ)
            {
                flag=1;
                display();
            }
        }
    }    
}
void TI0()interrupt 1
{
    count++;
    TR0=0;
    TH0=(65536-50000)/256;
    TL0=(65536-50000)%256;
    TR0=1;
}
void display()
{
        n=(int)(u*100);
        a[0]=n/1000;
        a[1]=n/100%10;
        a[2]=n/10%10;
        a[3]=n%10;
    if(flag==0)
    {             
        for(k=0;k<4;k++)
        {
            P0=wei[k];
            P2=duan[a[k]];
            delay(2);
        }
    }
        else if(flag==1)    
        {         
            P1=0;
            for(k=0;k<4;k++)
            {
            P0=wei[k];
            P2=0xc8;
            }
        }    
}