#include <stdio.h>
#include <conio.h>
#include <alloc.h>
#include <dos.h>
#include <bios.h>

struct boot
{
    unsigned char jump[3] ;
    char OEMname[8] ;
    shortint bps ;
    unsigned char spc ;
    shortint reservedsec ;
    unsigned char fatcopies ;
    shortint maxdirentries ;
    shortint totalsec ;
    unsigned char mediadesc ;
    shortint secperfat ;
    shortint secpertrack ;
    shortint noofsides ;
    longint hidden ;
    longint hugesec ;
    unsigned char drivenumber ;
    unsigned char reserved ;
    unsigned char bootsignature ;
    longint volumeid ;
    char volumelabel[11] ;
    char filesystype[8] ;
    unsigned char unused[450] ;
} ;

struct boot bs ;
char filetypestr[8] ;

void getfat_12 ( unsigned char * ) ;
void read_fat_info ( long ) ;
void fat_info( ) ;

void main( )
{
    char choice ;

    clrscr( ) ;

    printf ( "A. Drive A" ) ;
    printf ( "\nC. Drive C" ) ;
    printf ( "\n0. Exit" ) ;

    printf ( "\nEnter the drive (A/C): " ) ;
    scanf ( "%c", &choice ) ;

    if ( absread ( choice - 65, 1, 0, &bs ) == -1 )
    {
        printf ( "Error reading sector" ) ;
        exit ( 0 ) ;
    }
    else
    {
        strcpy ( filetypestr, bs.filesystype ) ;
        filetypestr[6] = '\0' ;
    }

    fat_info( ) ;
}

void getfat_12 ( unsigned char *pfat )
{
    intvalue ;
    int *fatentry ;
    int i, k ;

    for ( k = 2 ; k < 18 ; k++ )
    {
        i = k * 3 / 2 ;

        fatentry =  ( int* ) ( pfat + i ) ;

        if ( ( k % 2 ) == 0 )
            value = ( *fatentry & 0x0fff ) ;
        elsevalue = ( *fatentry >> 4 ) ;

        printf ( "%03x   ", value ) ;
        if ( k % 9 == 0 )
            printf ( "\n" ) ;
    }
}

void read_fat_info ( long fat_num )
{
    int j, i ;

    unsigned char *p ;

    if ( strncmp ( "FAT12", filetypestr, 5 ) == 0 )
    {
        p = ( unsigned char* ) malloc ( bs.bps ) ;
        absread ( 0, 1, fat_num, p ) ;
        getfat_12( p ) ;
    }

    if ( strncmp ( "FAT16", filetypestr, 5 ) == 0 )
    {
        shortint *pfat ;
        p = ( unsigned char* ) malloc ( bs.bps ) ;
        absread ( 2, 1, fat_num, p ) ;
        pfat = ( shortint* ) p ;

        for ( j = 0 ; j < 2 ; j++ )
        {
            printf ( "\n%d   ", j * 8 ) ;
            for ( i = 0 ; i < 8 ; i++ )
            {
                printf ( "%04x  ", *pfat++ ) ;
            }
        }
    }
}

void fat_info( )
{
    longint first_fat, second_fat ;

    first_fat = bs.reservedsec ;
    second_fat = bs.reservedsec + bs.secperfat ;

    printf ( "\n%s Fat Information", filetypestr ) ;
    printf ( "\n-------------------------------" ) ;

    printf ( "\nFirst FAT Information\n" ) ;

    read_fat_info ( first_fat ) ;

    printf ( "\n\nSecond FAT Information\n" ) ;

    read_fat_info ( second_fat ) ;
    printf ( "\n-------------------------------\n" ) ;
}