BACK IN THE GOOD old days of Richard Nixon and Spiro Agnew, there was a lot of talk about everything called law 'n' order. Just exactly what that meant -- police oppression or good, clean law enforcement -- depended a great deal on who you were. It was an example of political code: It could mean anything you wanted it to mean.

Politicians love to speak in code. Jimmy Carter does it when he talks of character but really means Chappaquiddick, or when he promised us the sort of government we deserve and then leaves you wondering four years later whether we got it.

The real master at political code though, is not Carter but Ronald Reagan. Strictly from that standpoint, his speech to the GOP convention was a beaut. It was in that speech that he once again mentioned what he called "the shared values of family, work, neighborhood, peace and freedom." We all know -- wink, wink -- what he really means.

Family, of course, does not, strictly speaking, mean family. It means no Equal Rights Amendment and no abortion. It means no gays and no living together and no smooching or worse before marriage and no married women with hypenated names and the prefix Ms. before them. If you know anything at all about Ronald Reagan, you know that "family" does not mean three homosexuals and two women living with their children by another marriage in a converted tenement in the inner city.

The next code word on the list, work, really doesn't refer to work at all, but what you might want to call no work -- specifically, how we all feel about those who don't. It means no welfare. It means no food stamps. It means none of the social welfare programs that the Democrats have enacted lo these many years since the nation veered from the Turth Path and elected Franklin D. Roosevelt.

"Neighborhood" comes in crystal clear. It is white. It does not bus its schoolchildren. It has lawns and kids on bikes and paper boys and picket fences. It does not have busing (forced or otherwise) or public housing or tenements or black people. These kinds of places are not called neighborhoods anyway. They are called "the community," which is still more code for a place where black people live. In America," the community" is always black; the "neighborhood" is always white.

All political codes have to be based to a certain extent on truth and on what Reagan calls shared values, or they will not work. The code word "work," for instance, is effecting not only because it is an appeal to America's lingering antiwelfare sentiment, but because it also encapsulates real, pragmatic concerns about worker productivity and the attitude of people who really will not work and think that this is not their problem, but the government's.

In this sense, political codes are different from euphemisms. A euphemism is something like "Right to Life," which is just antiabortion all dressed up, or "Right to Work," which is just antiunionism in its Sunday Best: Political code is more like being told a girl has a "nice personality," which, while undoubtedly true, also means that she looks like Seattle Slew.

In Reagan's case, the code words incorporate a basic political philosophy. You know what he means when he says the code words because they are in some way like flags: They represent something bigger. In the case, they are words he has been using since at least 1978, and they have been motifs in his speeches since April or so of this year.

For instance, freedom, the next word on the list, has nothing to do with freedom in the Bill-of-Rights sense of the word or anything that might concern the American Civil Liberties Union. It is, instead, another way of saying, "get the federal government off the back of business." Freedom is the freedom to conduct business more or less the way business wants. A key part of the concept is freedom from high taxes. t

The last code word -- peace -- is both the most simple and the most complex. It is complex because it is not about peace at all, but about such things as the defense budget and rearming and the cruise missile and SALT -- the sort of military might and posture that is supposed to give the Soviets pause before they mess with us. That is the way Reagan supporters hear the word.

Others who disagree with Reagan hear it differently. When Reagan said "peace," they heard "war."

That's the trouble with talking in political code. It lets the listeners think what they want.