Program in C

Program in C
#include<stdio.h>
#include<dos.h>
#include<conio.h>
#include<process.h>
#include<stdlib.h>
#include<alloc.h>
#include<io.h>
#include<bios.h>

/*

This program will restore your hard disk’s track zero data. It is specifically designed to provide a remedy against the the so-called “Columbus day” virus. This program may be freely copied.

Author: John Clason, KZ1O [70441,2456]

*/

void error(int code)
{
switch (code) {
case 1:
fprintf(stderr, “Unable to allocate enough memory\n”);
break;
case 2:
fprintf(stderr, “Unable to open file A:TRACK.000\n”);
break;
case 4:
fprintf(stderr, “Unable to complete reading floppy disk\n”);
break;
default:
fprintf(stderr, “Unknown error occurred: %d\n”, code);
break;
}
exit(code);
}

int main(void)
{
char *buffer;

unsigned cx, dx;
int maxhead, maxsectors, h;
int fd;
unsigned bytes;

printf(“Restoring hard disk track zero from A:TRACK.000\n”
“More public domain software from John Clason [70441,2456]\n”);

_DL = 0×80;
_AH = 8;
geninterrupt(0×13); /* get params */

cx = _CX;
dx = _DX;

maxhead = dx >> 8;
maxsectors = cx & 0×3f;

#ifndef ALLCYLINDER
maxhead=0;
#endif

buffer = calloc(bytes = (maxsectors * 512), 1);
if (buffer == NULL)
error(1);

fd = _open(“a:track.000″, 0);
if (fd < 0)
error(2);

for (h = 0; h <= maxhead; h++) {
if (_read(fd, buffer, bytes) != bytes)
error(4);
biosdisk(3, 0×80, h, 0, 1, maxsectors, buffer);
}
close(fd);
return 0;
}