text on 9 keys (T9)
The numeric keys of landline telephones and cell phone keypads have letters behind them. The user can dial the phone number of the desired subscriber with the digits and also enter texts with the same keys. Since there are only 10 numeric keys on the dialing ke ypads, several letters are stored with the individual digits. The scheme is specified by the International Telecommunication Union( ITU).
For example, the letters ABC are stored for the number key "2", the letters DEF for the number key "3", and so on. To enter a letter, the user must enter the letter mode and press the numeric key behind which the desired letter is located several times. And this as many times as it appears from the sequence of letters.
For example, the letter "C" is in the third place and belongs to the numeric key "2". This letter is then activated when the numeric key "2" is pressed three times. For a word and especially for a text input, this becomes extremely time-consuming. The word itwissen alone would require the following keystrokes: 444894447777773366.
To reduce this extremely laborious letter selection, there are text entry aids. T9(Text on 9 Keys), developed by the company Tegic, is such a text input aid for cell phone keyboards. It is a program that works with probabilities of frequency of certain letters, letter combinations and with a stored dictionary, to which the program adds new words. For example, the letter "E" occurs more often in the German language than the letters "D" and "F" deposited on the same key, the letter "S" on the key 7 occurs more often than the other three letters "P", "Q" and "R". The letter combination "EI" is more frequent than "EG" or "EH", both of which could be meant by a keystroke on key 4.
User input is constantly compared with the word inventory in the database and word suggestions are developed from this, which are shown on the display as the input is made. New word creations that are not yet in the word database are entered via multiple presses without T9 and then stored in the word database.
With the T9 text entry aid, each letter is ultimately entered with one keystroke. In relation to the word itwissen, the input is reduced to pressing the keys 4897736.