Convert Roman Numeral to Decimal

/* Write a C program to convert a Roman numeral to its decimal equivalent. */

#include<stdio.h>

#include<conio.h>

#include<string.h>

#include<stdlib.h>

void main()

{

 int *a,len,i,j,k;

 char *rom;

 clrscr();

 printf("Enter the Roman Numeral:");

 scanf("%s",rom);

 len=strlen(rom);

 for(i=0;i<len;i++)

 {

  if(rom[i]=='I')

  a[i]=1;

  else if(rom[i]=='V')

  a[i]=5;

  else if(rom[i]=='X')

  a[i]=10;

  else if(rom[i]=='L')

  a[i]=50;

  else if(rom[i]=='C')

  a[i]=100;

  else if(rom[i]=='D')

  a[i]=500;

  else if(rom[i]=='M')

  a[i]=1000;

  else

  {

    printf("\nInvalid Value");

    getch();

    exit(0);

  }

}

k=a[len-1];

for(i=len-1;i>0;i--)

{

  if(a[i]>a[i-1])

  k=k-a[i-1];

  else if(a[i]==a[i-1] || a[i]<a[i-1])

  k=k+a[i-1];

}

printf("\nIts Decimal Equivalent is:");

printf("%d",k);

getch();

}