PIC microcontroller AD interrupt debugging (without digital filtering)

The interrupt debugging program of PIC microcontroller AD conversion is as follows (without digital filtering):

#include
#define uchar unsigned char
#define uint  unsigned int
__CONFIG(0x3B31);
const uchar disp[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f};
uint adval;
float advalf;
uchar flag;
void delayms(uint x)
{  
   uint j,k;
   for(j=x;j>0;j--)
      for(k=110;k>0;k--);
}
void display(uint x )
{  
 PORTD= disp[x/1000]|0x80;
    PORTA= 0xF1;
    delayms(1);
  
    PORTD= disp[x/100%10];
    PORTA= 0xF3;
    delayms(1);

    PORTD= disp[x/10%10];
    PORTA= 0xF5;
    delayms(1);

    PORTD= disp[x%10];
    PORTA= 0xF7;
    delayms(1);
}
void init()
{
 uint adval=0;
    float advalf=0;
 flag = 0;
    TRISA=0x01;
    TRISC=0;
    PORTC=0x01;
    TRISD=0;
  
    ADCON0=0x41; //8-division (4M), AN0, enable ADC
   ADCON1=0x8E; //right-align, AN0 channel
 ADRESH = ADRESL = 0;
 PIE1 |=0x40; //AD interrupt enable
 INTCON |= 0xC0; //Peripheral enable, global interrupt enable
 ADGO=1; //ADC conversion enable
    delayms(10);
}
void interrupt AD(void)
{
 if(ADIF&&ADIE) //AD interrupt enable and flag bit set 
 {
  ADIF = 0; //flag bit reset
  ADGO=0; //Pause AD conversion
  flag = 1; //Set flag bit
 }
}

void main()
{  
    init();
 while(1)
 {
  if(flag)
  { 
   flag = 0;
   adval=ADRESH;
      adval=adval<<8|ADRESL;
      advalf=adval/1023.0*5.0;
      adval=advalf*1000;
         ADGO=1;  //ADC转换使能
        display(adval);
  }
 }
}