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off ice. major

In addition, metropolitan

USPS points out that when taken together, areas would amount to a de facto national

local directories in all directory. Local mail

(about 40 percent of the total) would be processed using a local directory in the originating post office, and non-local mail (the other 60 percent) would be processed using local directories in the various destination post offices.

Nonetheless, OTA estimated the technical and cost requirements of a national directory, even though the need for such a directory has not been firmly established.

The memory size of a national directory has been grossly estimated at 20 gigabits

or 20 billion bits. A directory of this size would contain all 20 million ZIP+4 codes plus address information including street number and address, city, State, and, where necessary, building floor and suite numbers. The size could be reduced to include only the most frequently used ZIP+4 codes and related address information. For example, if 15 percent of ZIP+4 codes account for 75 percent of ZIP+4 code use, then a memory size of 3 billion bits might suffice.

Currently available magnetic disc memory technology can provide a 3 billion bit

capacity at a cost of about $30,000.

But

the average access time appears to be too

long. Optical

disc and

random access

memories

magnetic bubble (RAMs) have fast

memories have similar limitations. Large access times (microseconds as compared to

milliseconds) and may be the best approach. A 3 billion bit directory might cost on the order of $300,000 in 3 years (1987 dollars). If five directory, then the cost per OCR would be about $60,000.

using 256K RAMs OCRs shared each

now

[n sum, a coming on

national directory would be technically

the

market.

A

full

national

directory

feasible with of 20 billion

memory technology bits of information

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