If you love linear bar codes, you probably wore bow ties, carried plastic pocket protectors and had pimples in your technical high school.

But you probably also kept tabs on a virtual revolution in package shipping that occurred from bar codes, those mysterious blocks of thick and thin lines that began gracing all sorts of packages in the early 1980s.If you did, get set for the next revolution called "two-dimensional symbology," as different from bar coding as black-and-white television is

from color.

Barely larger than a postage stamp, the new labels can hold more information, inventors promise, than Lincoln's Gettysburg Address. Conventional bar codes, which shippers and carriers use to identify packages, usually hold only 40 to 80 characters of information.

"A lot of people are testing two-dimensional symbologies," said Doug Anderson, the American Trucking Associations' (ATA) director of technical service. He said he expects the new codes to be a key component to electronic data interchange (EDI) systems in the not-too-distant future.

With transportation companies tripping over each other to offer shippers faster, more-reliable and more-informed delivery services, it has become essential to replace manually operated systems with as much computer automation as possible.

A key reason that bar coding was invented was to provide carriers with more accuracy and speed in delivery. The ATA estimates that manual keypunching results in one error for every 100 to 300 keystrokes. Bar code scanning, by contrast, has an estimated rate of one error for every 300 million characters scanned, it said.

In addition, while scanning a bar code can take only about two seconds, a skilled keypunch operator can take up to three times longer to retype the information for transmission along the shipping chain. For huge carriers such as United Parcel Service Inc., which ships some 12 million packages daily, the time and accuracy difference can be huge.

But bar codes have limitations.

"It's purely a tracking number right now," said Earle Timothy, a senior engineer for UPS in the company's Danbury, Conn., research and development division, referring to the bar codes that grace UPS and other package carriers' shipments.

In its bid to maintain the lead in worldwide small package shipping, however, the company isn't stopping at bar codes. Mr. Timothy's division developed MaxiCode, UPS' two-dimensional symbology system. UPS is testing MaxiCode in its hub in Grand Rapids, Mich., which may be the basis for adoption throughout the $15 billion transportation company, Mr. Timothy said.

In transportation, bar codes are generally used to hold several characters and letters, designating a customer's invoice number or other identifying code. But as package carriage becomes more automated, shippers are calling for more complete data on each label.

"Now, in addition to tracking information, we can include postal code, country code, class of service, date of package pickup and we would probably include destination," he said of MaxiCode.

"These are services customers have asked for," he added. "But everybody is going to have different needs."

So far, the tests of the new systems have shown strong promise, although Mr. Timothy declined to predict when, or even if, the new system will be adopted throughout UPS' far-flung operations.

But he said the new system could be adopted by shippers with not too much trouble. The labels can be printed with any laser printer capable of 200 to 600 dots per inch, and hand-held readers could be as common as current laser readers are today, said Mr. Timothy.

Consolidated Freightways Inc., the Menlo Park, Calif., transportation giant, also is testing another form of two-dimensional symbology called the PDF-417, created by Symbol Technologies Inc., a high-tech development firm.

"We are getting closer and closer to a paperless freight document," said Gary Frantz, a CF spokesman. He said such developments are particularly beneficial for customers that use EDI, since all bill of lading data can be contained in one printed label that is scannable into the the mainframe computers owned by shipper, carrier and consignee.

As such inventions get closer to reality, the use of EDI is expected to skyrocket. While such systems vary, the systems permit carrier, shipper and consignee to share data via phone or private communications links.

Most major carriers have some form of EDI, as do most major shippers. But small and medium-sized carriers, faced with the expense of installing EDI systems in their computers, have sometimes been slow to catch on.

"EDI I believe is rapidly approaching becoming a requirement for major customers," said Jeff Crowe, chairman, president and chief executive for Landstar System Inc., the group of truckload carriers based in Shelton, Conn. ''Every month brings a new crop of EDI customers."

The problem, he said, is that not all customers have standard programs in their mainframes or personal computers that can read the data from the carriers' computers.

Some carriers blame shippers for this.

"We have generally found that, with EDI, carriers are more prepared to provide it than shippers are willing to use it," said Paul G. Taylor, president of Southeastern Freight Lines Inc., a large LTL in Columbia, S.C. ''Every LTL carrier has thousands of customers, and your larger ones are prepared, but they are a small portion of your base."

Mr. Taylor said shippers that are committed to partnerships with their carriers are the best EDI customers.

"I think, where the customer understands partnerships and is committed to partnerships, EDI does work and eliminate some paperwork," Mr. Taylor said.