A program for digital clock

A clock program is a simple graphical clock display to provide the time.The time is seconds,minutes and hours.The sample clock program in C language program is ,
void interrupt (*prevtimer)();
void interrupt mytimer();
int running=0;
int io=0,hours,sec,min;
unsigned long int far *time=(unsigned long far *)0x46C;char far *scr;char far *mode;struct time t;
void main()
{
if((*mode & 0x30)==0x30)scr=(char far *)0xB0000000L;elsescr=(char far *)0xB8000000L;
/*if(io==0)
{gettime(&t);
hours=t.ti_hour;
//(*time/65520);min=t.ti_min;
//(*time - hours*65520)/1092;sec=t.ti_sec;
//(*time-(hours*65520)-(min*1092))*10/182;io++;} */
prevtimer=getvect(8);
setvect(8,mytimer);
keep(0,1000);
}
void interrupt mytimer()
{
unsigned char hours,min,sec;
if(running==0)
{
running=1;
hours=(*time/65520);min=(*time - hours*65520)/1092;sec=(*time-(hours*65520)-(min*1092))*10/182;
if(sec>=60)
{
sec-=60;
min++;
if(min==60)
{
min=0;
hours++;
if(hours==24)hours=0;
}
}
writechar(48+hours/10,0,72,66);
writechar(48+hours%10,0,73,66);
writechar(':',0,74,66);
writechar(48+min/10,0,75,66);
writechar(48+min%10,0,76,66);
writechar(':',0,77,66);
writechar(48+sec/10,0,78,66);
writechar(48+sec%10,0,79,66);
writestring("Made by blogofnaveen.blogspot.com",0,44,66);
running=0;
}
(*prevtimer)();
}
NOTE:
The clock program is using important header files are dos.h and tsr.h.
Display only seconds,minutes and hours