/*
 *
 * Write a program that can convert a decimal to a hex value and vice-versa.
 * The program must pass a command line argument to determine what will
 * be the conversion type and the value to be converted. The value
 * must be evaluated to make sure it's valid before converting.
 * Otherwise, inform the user and terminate the program
 *
 * Author: Kun Deng
 */