ABC DEF GHI JKL MNO PRS TUV WXY

A long time ago in a galaxy far, far away...
telephone numbers used to include letters.
It was back in the days when phone numbers
were seven digits long.

For example in a particular suburb of Chicago,
Illinois, there were telephone numbers that
started with "BR" for Bryan or "TE" for Terrace.

Someone's telephone number may have been
Terrace-27093 (TE-27093) or Bryan-95546 (BR-95546)
where Terrace and Bryan represented a particular
area of town.  They were also the names of the
central offices where the phone numbers were serviced.

To accomodate these helpful mnemonics, the digits
2-9 each had three letters written above the digit
on the telephone dial as shown below:

ABC DEF GHI JKL MNO PRS TUV WXY
 2   3   4   5   6   7   8   9

The letters "OPER" appeared above the digit 0
but stood for "operator" and were not intended
to represent separate letters.

At that time it was well known that if
you wanted to dial a "Terrace" number,
you would find the "T" (above the 8) and
find the "E" (above the 3) and dial 83
before the rest of the telephone number.

Or if you wanted to dial a "Bryan" number,
you would find the "B" (above the 2) and
find the "R" (above the 7) and dial 27
before the rest of the telephone number.

Some time later, the rotary dial was replaced
with a touch-tone keypad that may look familiar:

    ABC DEF
 1   2   3

GHI JKL MNO
 4   5   6

PRS TUV WXY
 7   8   9

    OPER
 *   0   #

For advertising purposes, one large carpet company
acquired a phone number of 227-7387 which could be
dialed by pressing the letters C-A-R-P-E-T-S instead
of one having to remember a phone number.

Soon after that, banks figured out that it was possible
to enable automated banking over the phone by allowing
the caller to enter information using the touch-tone
keypad.

It didn't take long before telephones turned into remote
keyboards for many computerized consumer applications.

However, there was one small problem. If someone was trying
to enter a person's name that included a "Q" or a "Z" they
were nowhere to be found. Since there were no real standards
as to how this would be handled, two conflicting methods arose.

Many applications determined that the 1 digit could be used
for Q and Z since it never had any letters associated with it.

AT&T decided on their own that the 7 and 9 digits should be
expanded to accomodate these "missing" letters. So on every
AT&T telephone you will see "PQRS" above the 7 and "WXYZ"
above the 9.  This could get confusing when the voice on
the other end cleared said to use the 1 for Q and Z.

With the advent of advanced cell phone applications the issue
didn't exactly go away, but was replaced by another issue:
How can you efficiently type words on a keypad with the limited
keypad of a telephone.

Certain applications required that you press two buttons for each
letter: one for the button the letter appeared on, and next a digit
from 1-3 (or 1-4 for AT&T) for the position of the letter on the
button.

Other applications let you just press one button for each letter,
then would present you with the possible word/name choices that
matched the combination of digits pressed.

Yet other applications use a predictive method called T9 where
as you start pressing buttons the possible choices are presented
or predicted while you are "typing".