If you thought the Year 2000 computer bug was bad, just wait. Other problems that computers may  have with dates and data  could cost even more to fix and promise to extend well into the next  century.

The much-fretted Y2K problem, which arises from the way computers keep track of dates using two  digits instead of four, is  expected to cost the world between $600 billion and $4.6 trillion to fix.

Less familiar looming concerns include:

The European Union's conversion to the new euro currency starting in a few months;

The rollover of the date system in Global Positioning System satellites;

• America's surfeit of telephones for home and office, voice and data, threatening the possibility  that the nation could run  out of phone numbers; and

• Ditto Social Security numbers, which are not used again when people die.

  That's the warning of Capers Jones, chief scientist at Artemis Management Systems Inc. and  founder of Software  Productivity Research, which analyzes software development and   planning.

  "Starting next year, date and data corrections will dominate the software industry," said Jones,  "and the repairs will cost $5  trillion over the years 1999 to 2050." He predicted these problems,  along with Y2K, will damage the software industry for an entire generation.

  "The best we can hope for is a quick recovery,'' he said.

   

The European Union

The European Monetary Union will begin its conversion to the euro currency Jan. 1, 1999, and union  countries are  scheduled to phase out national currencies in 2004.

The euro conversion is the second largest software challenge in the world behind the Y2K problem,  said Jones, and it's  more sophisticated. Instead of changing every date in a computer system with a  single deadline looming, computer   systems have to be able to handle the different ways the 11  union countries change over. Further complicating the  problem are individual companies that may  convert completely to conducting business in euros, or they may continue to  track their national  currency while simultaneously using the euro.

Ed Severs, chief operating officer for ADPAC Inc., one of the older companies designing mainframe  computer systems,  said there aren't enough programmers to finish both the euro conversion and  the Y2K fix.

Jones said about 10 million programs, ranging from Microsoft's spreadsheet software, Excel, to  specialized financial  tracking software, would have to be modified to handle the euro conversion.

France and Germany, said Gary Fisher, a computer scientist at Information Technology Laboratory at  the U.S. National  Institute of Standards and Technology, are putting all their resources into  converting to the euro instead of Y2K.   ``They're in a fix, I think,'' he said. ``They're going to be   fighting fires everywhere.''

The euro conversion could cost between $150 billion and $400 billion spread among the 11 union  countries, said Severs.  Jones agreed and said 70 percent of the cost likely would be borne by the  union countries, with the rest falling on   companies around the world that deal with the union and  track European currencies.

``If you're a financial institution (doing business in Europe), you're going to spend between three and  five times what you  did on Y2K,'' said Severs.

GPS satellites

In the period between the euro conversion and Jan. 1, 2000, the belt of 24 satellites making up the  Global Positioning System is programmed to reset its date system. This could cause problems in  navigation and power plants, and even in the calculation of interest for international financial  transactions.

The network, run by the Defense Department, allows anyone with a GPS receiver to pinpoint their  position on the Earth to within about 330 feet. The satellites keep track of dates by measuring the  number of weeks elapsed since Jan. 5, 1980. Every 1,024 weeks, the timer resets to zero; that will  occur at midnight Aug. 21, 1999.

The satellites use the elapsed week count to account for variations in the earth's orbit and rotation.  That's why civilian Earth-based receivers, not programmed to handle the rollover, could have  problems determining the location, Fisher said.

``The receivers are going to have to become compliant, either through a new chip or new software,''  said Fisher. ``And the satellites that have the problems will have to be replaced.''

GPS dates also are used to synchronize some electrical power plants and large international  transfers of funds. Jones worries that the rollover might cause some plants to quit working, and  interest payments on the transfers could be thrown off.

For instance, if it takes a second to transfer $1 billion between two banks in different countries, the  interest could be a few hundred dollars. But if one of the banks, relying on the GPS satellites, hasn't  planned for the date rollover, its computers could think the transfer took 20 years. The interest could  be off by trillions of dollars in that case.

Because the rollover's timing, computer systems handling large financial systems will need to be  checked for euro, GPS date and Y2K compliance all at the same time.

``It's in the international standards, so it shouldn't be a surprise,'' said Jones. ``But Year 2000 should  have been obvious, too.''

Phone numbers

Last year, Arkansas gained a new area code after decades of a single code. In January this year,  western Massachusetts gained a new one as well. And new area codes seem to pop up weekly in the  Bay area, ground zero for the use of multiple phone lines in the home.

Usually, a new area code is a minor annoyance, necessitating minor costs in reprinting stationery  and business cards. But in about 10 years, the number of phone lines needed will exceed the  capacity of a three-digit area code with a seven digit phone number. Jones suggests a five digit area  code and a nine-digit phone number to allow up for to a trillion individual phone lines -- enough for   several phone numbers for every person on the planet.

Problem solved? Nope. Millions of software applications in the United States can handle only  three-figure area code and seven-figure phone number. To upgrade them all will be cumbersome and  expensive.

Any lengthening of the phone number probably won't be a problem for telecommunications and  directory companies, Jones said, but large private and corporate phone lists will have to be updated.  This could be a problem if the program is configured to accept only the current format.

Jones estimates about 25 million software applications will need to be fixed.

Social Security

And if all that wasn't enough, the United States might run out of Social Security numbers.

Numbers assigned to U.S. citizens are not reused once someone dies. The current nine-digit system  provides a maximum of about 1 billion numbers. Since 1936, when the first number was issued, more  than 381 million numbers have been assigned, with about 6 million new ones issued each year.

It's easy to add a digit, but thousands of computer programs that expect nine-digit numbers will have  to be modified. Cost? Equal that of the Y2K bug in the United States, Jones figures.

The grandchildren of today's programmers will be solving that one, when the current numbers run  out around 2075.