Program in C to 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();

}