In the mid 1990s, as many industries began to assess their vulnerability to the Y2K bug, they realized the enormous breadth and depth of the potential impact. First, since adoption of the two-digit year convention by programmers had been nearly universal, virtually any function controlled by computer or containing an embedded computer might be affected. Problems could occur in missile defense systems, air traffic control,streetlights, telephones, water and electric power, and an endless list of other functions in other industries. Second, it was impossible to know which applications would be affected without testing. Applications were generally inadequately documented to identify which programs had the Y2K bug and where it existed within the program. Third, the problem was worldwide. Nearly every person on earth depended on services or businesses that were susceptible to the Y2K bug in some way. Most services and business were so interdependent that if some failed because they could in turn cause the failure of other business and services