When former postmaster general William F. Bolger announced in 1978 the U.S. Postal Service's plan to add four digits to the zip code, he didn't realize he would provoke a crusade against government-imposed numeration.

But the thought of committing those extra numbers to memory gave many Americans a headache, and they sought relief from Washington.

Sen. David F. Durenberger (R-Minn.), citing a study that said the average person has difficulty remembering more than seven consecutive numbers, called the nine-digit zip "a mnemonic plague of contagious digititis."

Yet in spite of complaints and a two-year delay imposed by Congress, the nine-digit zip prevailed. Now, a $900 million automation program undertaken by the Postal Service hinges on the success of the longer code. And questions about its effectiveness are at the core of a scandal under investigation by the Postal Inspection Service in cooperation with Justice Department, the Securities and Exchange Commission and the General Accounting Office.

So far, few describe the nine-digit zip as a triumph. Some call it a flop; others say it shows encouraging signs of growth.

It all started in 1975, when a five-member task force began examining ways to speed mail delivery and cut costs in a service that spends 80 percent of its budget on personnel. Their solution was to increase the number of existing zip codes from 40,000 to 21 million by tacking on four extra digits -- a plan designed primarily to improve handling of business mail, which makes up 85 percent of the 70 billion to 72 billion first class letters mailed each year.

Optical character readers would scan the zip codes and place bar codes on the letters. Other machines then would sort the letters to the carrier route, saving time and labor costs. Bolger's announcement of the plan in September 1978 set a 1981 starting date.

Then, the zap-the-zip campaign began. The House Government Operations Committee published a report charging that postal managers had "repeatedly overstated and misrepresented" benefits of the program.

Congress, responding to public indignation and doubts about management projections, ordered a two-year delay in implementing the longer zip code.

When the Postal Service finally launched the program in 1983, mail volume fell far short of expectations. By 1985, only 6.1 billion letters -- less than 10 percent of first class mail -- contained the nine-digit zip. Postal managers in 1980 had projected a volume of 22 billion pieces after two years.

Postal officials have attributed the program's slow start to overly ambitious projections, the delay imposed by Congress, a detrimental discounting policy set by the Postal Rate Commission, and incorrect public perceptions of the program, which was aimed at large business mailers and not the public.

"It isn't that we didn't go out and tell people about it and write stories about it and run ads about it," Bolger said. "It was probably one of those things with numbers in people's lives that obviously turned people off, or we didn't get the message across to them."

For the past year, there has been a deep new wrinkle in the debate over the nine-digit zip, which postal management contends is threatened by new technology endorsed by the postal board of governors.

In May 1985, following a recommendation from its technology committee, the board ordered the Postal Service to buy machines that could read an entire four-line address, rather than just a single line containing the zip code. Some postal managers felt the board's policy would undermine acceptance of the nine-digit zip. "We didn't see how you market the need for zip-plus-four if at the same time you were telling the universe that you have a machine that can do that for you," said James V. Jellison, former senior assistant postmaster general for operations.

In November 1985, board member Ruth O. Peters sent a letter to Postmaster General Paul N. Carlin questioning management's commitment to the "multi-line" technology. Later that month, Peters sent a memo to her fellow governors suggesting that management was creating obstacles to delay procurement and possibly was trying to thwart the board's policy.

Although members of Congress accused the governors of meddling in management, some observers contend that management needed to be pushed. "The postal management is so obtuse, so bull-headed, that they won't listen to their board of governors," Postal Rate Commissioner John W. Crutcher said.

The board's motives in pushing procurement have been questioned since former board vice chairman Peter E. Voss pleaded guilty May 30 to charges that he took kickbacks in a scheme to steer the award for multi-line equipment to a Dallas firm, Recognition Equipment Inc. (REI), one of two firms competing for the contract, estimated to be worth $250 million.

Following Voss' admission, members of Congress ordered an investigation of procurement practices and postal management postponed competition for the multi-line contract.

Some, however, say the governors were correct to push for multi-line equipment. "I've been critical of the governors, but in this respect, they are absolutely as clean as a hound's tooth," Crutcher said.

"Certainly it was correct to explore and evaluate the two firms and whether or not their equipment would live up to their claims," said Rep. Glenn English (D-Okla.), chairman of the Government Operations subcommittee on government information. "I think that made a lot of sense, and quite frankly still does. But the Peter Voss issue muddies the water and it's probably going to delay the determination."

Board member Peters stands by her committee's decision: "The fact that Peter Voss happened to enhance himself personally does not mean it wasn't the correct decision."

Voss said he supported multi-line technology long before he made his arrangement with a Michigan public relations firm representing REI to help steer the contract to the Texas company. "I felt very strongly that the Postal Service was making poetry out of statistics, and that the zip-plus-four philosophy was definitely wrong. I still feel that way . . . and I felt that long before I met REI, and that's a matter of public record."

For now, the nine-digit zip code is the state of the art. Although more business mailers are using the nine-digit zip, many are doubtful that the program will reach the 90 percent level originally projected by the Postal Service for 1989. "There's skepticism in the marketplace," said Van Seagraves, publisher of Business Mailers Review.

The Postal Service continues an aggressive campaign to tap the top 4,000 business mailers, who generate 43 percent of first class business mail. Those mailers have not yet flocked to the program.

Among other things, discounts have been offered for regionally sorted mailings over 500 containing the nine-digit zip. Postal Service spokesman Jim Van Loozen said many mailers view the half-cent per piece discount for these mailings as insufficient. Mailers have to update their software -- which include the lists by which they do massive computer mailings -- to add the extra digits. According to industry watchers, some don't consider it worth the effort.

About 25 percent of first class mail, or 17 billion pieces, is presorted by five-digit zip code before it goes through the Postal Service. Van Loozen said these simple presorting discounts -- 4 to 5 cents per piece -- have eclipsed discounts for the nine-digit program. "It's almost like a competing rate structure," he said.

Postal managers initially hoped to attract presorting companies, which process other businesses' mass mailings, to the nine-digit zip program, a notion that strikes some postal experts as naive. "A lot of the presort people think it's a dagger pointed straight at their throat," said Postal Rate Commissioner Crutcher.

Presorters feel threatened because as use of the nine-digit zip increases, the Postal Service will have less incentive to give discounts for work it can do as efficiently.

While postal managers figure how to attract the 25 percent who presort, they must also determine how to penetrate the remaining 75 percent of the business market. Van Loozen said the Postal Service is offering to help smaller mailers update their lists with new nine-digit zip codes. "The principal benefit is that they get list integrity. There are a lot of address hygiene problems," Van Loozen said, referring to incorrect or insufficient information on envelopes.

Meanwhile, Van Loozen points out that the volume for zip-plus-four -- as the Postal Service calls it -- tripled in 1985, and asserts that it is the fastest-growing program the Postal Service has ever introduced. "We don't regard the program as a failure," he said, "although some people often try to categorize it that way." The Postal Service projects 10.3 billion pieces for this year and 15 billion for 1987.

Whether the addition of multi-line readers will hurt acceptance of the nine-digit zip remains to be seen. Although tests in Phoenix between REI and ElectroCom Automation Inc. of Arlington, Tex., have been postponed, the Postal Service is committed to multi-line, which it will use in tandem with single-line machines.

Until then, for those who think the nine-digit zip will never catch on, Van Loozen has a handy comparison: It took the American public 13 years to accept the five-digit zip.