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Comprehensive Guide to BIOS and DOS Interrupts for Date and Time Management in C

This lecture provides an in-depth exploration of using BIOS and DOS interrupts in C programming for managing system date and time. It details the methods to retrieve and update the current date, including century, year, month, and day. The lecture also covers interrupt handling for time updates and demonstrates how to read user input for setting the system clock. Students will gain knowledge of how to interface with low-level hardware through interrupts, enhancing their understanding of systems programming.

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Comprehensive Guide to BIOS and DOS Interrupts for Date and Time Management in C

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  1. Lecture 19

  2. #include <bios.h>#include <dos.h>void main (){ unsigned int cen,yrs,mons,days; _AH =4; geninterrupt(0x1a); cen=_CH; yrs=_CL; mons=_DH; days=_DL; cen = cen <<4; *((unsigned char *)(&cen)) = (*((unsigned char *)(&cen))) >>4; cen = cen + 0x3030;

  3. mons = mons <<4; *((unsigned char *)(&mons)) = (*((unsigned char *)(&mons))) >>4; mons = mons + 0x3030; yrs = yrs <<4; *((unsigned char *)(&yrs)) = (*((unsigned char *)(&yrs))) >>4; yrs = yrs + 0x3030; days = days <<4; *((unsigned char *)(&days)) = (*((unsigned char *)(&days))) >>4; days = days + 0x3030; clrscr();

  4. printf("%c%c-%c%c-%c%c%c%c", *(((unsigned char*)(&days))+1), *((unsigned char*)(&days)), *(((unsigned char*)(&mons))+1), *((unsigned char*)(&mons)), *(((unsigned char*)(&cen))+1), *((unsigned char*)(&cen)), *(((unsigned char*)(&yrs))+1), *((unsigned char*)(&yrs))); getch();}

  5. unsigned char ASCIItoBCD(char hi, char lo){ hi = hi - 0x30; lo = lo - 0x30; hi = hi << 4; hi = hi | lo; return hi;}void main (){ unsigned char yrs,mons,days,cen; char ch1, ch2; puts("\nEnter the century to update: "); ch1=getche(); ch2=getche(); cen = ASCIItoBCD(ch1, ch2);

  6. puts("\nEnter the yrs to update: "); ch1=getche(); ch2=getche(); yrs = ASCIItoBCD(ch1, ch2); puts("\nEnter the month to update: "); ch1=getche(); ch2=getche(); mons = ASCIItoBCD(ch1, ch2); puts("\nEnter the days to update: "); ch1=getche(); ch2=getche(); days = ASCIItoBCD(ch1, ch2); _CH = cen;_CL=yrs;_DH= mons; _DL=days; _AH =5; geninterrupt(0x1a); puts("Date Updated");}

  7. void interrupt (*oldint)();void interrupt newint();unsigned int far * scr = (unsigned int far *)0xb8000000;void main (){ oldint = getvect(0x4a); setvect(0x4a, newint); _AH=6; _CH =0x23; _CL=0x50; _DH=0; geninterrupt(0x1a); keep(0,1000);}void interrupt newint(){ *scr=0x7041; sound(0x21ff);}

  8. #include <bios.h>#include <dos.h>void interrupt newint70();void interrupt (*oldint70)();unsigned int far *scr = (unsigned int far *)0xb8000000;unsigned char ASCIItoBCD(char hi, char lo){ hi = hi - 0x30; lo = lo - 0x30; hi = hi << 4; hi = hi | lo; return hi;}

  9. void main (void){ int temp; unsigned char hrs,mins,secs; char ch1, ch2; puts("\nEnter the hours to update: "); ch1=getche(); ch2=getch(); hrs = ASCIItoBCD(ch1, ch2); puts("\nEnter the minutes to update: "); ch1=getche(); ch2=getch(); mins = ASCIItoBCD(ch1, ch2);

  10. puts("\nEnter the seconds to update: "); ch1=getche(); ch2=getch(); secs = ASCIItoBCD(ch1, ch2); outportb(0x70,1); outportb(0x71,secs); outportb(0x70,3); outportb(0x71,mins); outportb(0x70,5); outportb(0x71,hrs); outportb(0x70,0x0b);

  11. temp = inport(0x71); temp = temp | 0x70; outportb(0x70,0x0b); outportb(0x71,temp); oldint70 = getvect(0x70); setvect(0x70, newint70); keep(0,1000);}void interrupt newint70(){ outportb(0x70,0x0c); if (( inport(0x71) & 0x20) == 0x20) sound(0x21ff); *scr=0x7041; (*oldint70)();}

  12. Determining Systems Information INT 11H INT 12H INT 11H used to get hardware environment info. On Entry call 11H On Exit AX = System Info.

  13. Determining Systems Information INT 12H used for memory interfaced. INT 15H/88H Returns = No. of KB above 1MB mark.

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