51單片機，計數溢出

請以下面程序為例解釋解釋

//用T0使隔1秒流水燈亮一次，用T1使隔2秒靜態數碼管依次顯示數字
#include
#include
#define uint unsigned int
#define uchar unsigned char
uchar tcount0,tcount1,temp,num;
uchar code table[]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,
0x90,0x88,0x83,0xc6,0xa1,0x86,0x8e};
void main()
{
TMOD=0x11;
TH0=(65536-50000)/256;
TL0=(65536-50000)%6;
TH1=(65536-50000)/256;
TL1=(65536-50000)%6;
EA=1;
ET0=1;
ET1=1;
num=0;
temp=0xfe;
tcount0=0;
tcount1=0;
TR0=1;
TR1=1;
while(1);
}
void t0() interrupt 1//計數溢出，CPU響應中斷
{
TH0=(65536-50000)/256;
TL0=(65536-50000)%6;//設定回計數初值，但此時計數溢出后已清0仍在計數嗎？
tcount0++;
if(tcount0==20)
{
tcount0=0;
P1=temp;
temp=_crol_(temp,1);
}
}
void t1() interrupt 3
{
TH1=(65536-50000)/256;
TL1=(65536-50000)%6;
tcount1++;
if(tcount1==40)
{
tcount1=0;
if (num==16)
num=0;
P0=table[num];
num++;
}
}