Half a year ago today, jubilant Germans broke through the Berlin Wall, and in the ensuing euphoria some aggressive U.S. companies have moved into East Germany.

Others, however, are still waiting for a Western-style legal framework to be set up and for the deutsche mark to be named the official currency of East Germany.Companies holding back until currency union won't have a long wait. The deutsche mark is scheduled to become East Germany's official currency on July 2.

A legal framework is expected to take longer, but East German officials have already said they want to adopt a tax system modeled on West Germany's.

Still unresolved is the tricky political problem of land ownership.

Despite such uncertainties, several major U.S. corporations have announced either joint ventures or independent investments.

Here's an overview of U.S. investment in East Germany. Rather than a comprehensive listing, it is intended to give a general idea of which companies are doing what in East Germany.

CONSUMER PRODUCTS - One of the biggest players in this wide-ranging sector is Coca-Cola Deutschland GmbH, the West German subsidiary of Coke, which plans to invest $140 million and open six bottling plants, somewhat fewer than the 10 initially foreseen. Meanwhile, Pepsi-Cola GmbH has signed an agreement with VEB OGS, an East German state-owned chain of stores that will carry Pepsi products, which East Germans can buy with East German marks.

GM-owned Adam Opel AG is negotiating a joint venture with Automobil Werk Eisenach, a state-owned car company. Opel has released few details of the deal, except to say that it wants to produce 150,000 cars annually, and is seeking a majority stake in the deal.

Both Kraft Inc. and Procter & Gamble Co. are eyeing the East German market, but P&G is waiting for the currency union to take place. "Our products are made in West Germany, and their costs are based in deutsche marks," said P& G's Christel Karesch, adding that market studies are needed to determine which products will interest East Germans.

Levi Strauss & Co. wants to sell jeans in East Germany, but it can't even meet demand in West Germany. The company's products, like those of P&G, have long been available for hard currency in East German shops that cater to tourists, and a recent marketing study showed that the Levi brand name is one of the most recognized in East Germany.

COMPUTERS - IBM GmbH, the U.S. computer giant's West German subsidiary, has signed agreements with 11 East German computer centers for software development. Big Blue also opened an office in West Berlin at the beginning of this year to serve the East German market. In addition, IBM has a joint venture with a division of East German computer maker Kombinat, Robotron that will focus on medium-sized computers.

NCR GmbH, the Dayton, Ohio-based company's West German subsidiary, has a joint venture with Robotron's export-import division to sell NCR cash registers and personal computers to small and medium-sized companies. NCR also

plans to sell larger systems on its own.

Digital Equipment Corp. recently opened an office in West Berlin to pursue East German business. According to DEC's Theresa Wermels-Kirchen, the company wants to concentrate on education and software development, but is also selling such machines as its Microvax II. DEC is not looking for an East German joint-venture partner; instead, it aims to sell its machines directly, using both East and West German sales personnel.

BANKS - U.S. banks have been much more cautious than their West German counterparts in seeking to expand their business eastward. Analysts say that, having been burned in Latin America, most U.S. banks are unwilling to get involved once again with less than stable economies.

Still, one U.S. bank is taking the plunge. Citibank has filed applications with East German authorities to open representative offices in East Berlin, Leipzig and Dresden. Citibank already has experience in Eastern Europe, holding a majority stake in Citibank Budapest. Its East German offices are expected to be converted to subsidiary branches once the legal framework is in place.

EXPRESS MAIL SERVICES - Federal Express Corp. last week opened an office in West Berlin to serve both sides of the city, and the company plans to open offices in Leipzig, Dresden and Karl Marx Stadt. DHL Worldwide Express has been active in East Germany since 1986, conducting operations from a West Berlin office. United Parcel Service Inc. began delivering to all East German cities on April 17.