The post office has your number -- all nine of them

10036-4987 Got that? That's what the new, expanded nine-digit Zip Code is going to look like come February, when the US Postal Service gives Americans what many may not know they need but what Uncle Sam assures them they really do -- four more numbers to memorize.

Now, lest those skeptics who have been complaining that the post office is trying to do a number on them be too quick to pooh-pooh this latest proposed advance in automated mail handling, we urge a quick perusal of the other commonly used numbers in your wallet. The new Zip Code is certainly no longer than the ever dependable nine-digit social security number or even the nine-digit driver's license Massachusetts and other states hand out. In fact, next to the 11-digit phone number in most large cities or the 15-digit computerized banking card found in many a wallet, remembering the Zip Code promises to be a breeze.

Still not convinced? Well, neither are some other Americans, it would appear , and to counter the negativism that persists among small businesses and others, the Postal Service has launched a vigorous defense of its plan. Among other things, postal officials stress that use of the nine-digit code will be strictly voluntary; no one will be forced to memorize those last four digits.

Although there is no promise that the longer Zip Code will speed up mail deliveries, it will increase efficiency and improve the reliability of mail service over the long run. The plan will allow the Postal Service to reduce its work force, cut costs, and thereby lengthen the time between postal rate increases. If the program reaches its full potential, the cost savings to the Postal Service could reach $500 million a year. Although businesses will incur some initial change-over expenses, their savings in mail costs should be passed along to consumers in the form of lower prices.

Perhaps the most reassuring aspect of the plan is the Postal Service's promise that, once assigned, the new Zip Code will be permanent; there will be no need to add more digits in the future. Most letter-writers will no doubt give the added digits their stamp of approval -- and keep hoping that nine is enough.