Along with a sharp increase in a mobile internet industry, the use of a portable terminal such as a cellular phone, a PCS, a PDA, a PMP, a PSP, an electronic dictionary, a navigation terminal, UMPC, a laptop computer, etc. increases. So, various methods are developed for an easier letter input. However, still a certain letter input method, which is able to meet the needs for a convenience, quickness, accuracy and mobility, is urgently needed.
In a conventional letter input method of a potable terminal, there are a method in which letters are inputted step by step by searching and pressing the letters which are allocated to the numbers of 0 through 9, a method which uses a Qwerty keyboard or a LCD touch screen along with the Qwerty keyboard, and a method which uses a foldable keyboard.
When it is needed to transmit a SMS using a potable terminal, a user changes the potable terminal to a SMS input mode and inputs a certain message. In the calling mode, a keypad conventionally used as a dial button is used as a keyboard for a letter input.
For a Korean input method, various methods are disclosed. The Korean letter input method used in a conventional potable terminal is generally classified into a method in which consonants and vowels are separately inputted based on a so-called ChunJiln method for thereby combining and creating a certain letter, and a method in which a consonant and a finished vowel are separately inputted based on a so-called EuddumHangul method for thereby combining and creating a certain letter.
In the ChunJiln input method, the buttons of consonants and vowels are separated in the keypad of the potable terminal. “┐, •, -” corresponding to the vowels are allocated to the 1, 2, 3 keypads. The consonants are allocated to “4˜9, 0” keypads. So, a certain letter is combined with the consonants and vowels. In particular, since it is possible to express all vowels with only three buttons, a letter input on the potable terminal is easy.
In the EuddumHangul input method, a first input of the keyboard is performed with a consonant all the time. The first consonant of the next letter, which was finished with a first consonant and a final consonant of the first letter, is combined with a vowel all the time. So, a certain letter is combined with a vowel finished with a consonant based on a combined keyboard, so that it is easy to input a certain letter on the cellular phone.
However, since the consonants and vowels are set together on one keypad in the conventional Korean letter input method, a letter input motion occurs between far-spaced keys during the input of a letter.
In the English input method, 2˜4 English letters are allocated to one number keypad in the potable terminal which usually does not have a Qwerty keyboard, and a certain key is pressed once or two through four times in series for inputting a certain letter for thereby creating the letter. In the letter groups allocated to the same number keys, it is possible to input the next letter after a certain pressing time interval or by pressing a spacing key.
Therefore, when a certain key is repeatedly pressed or a certain time difference is provided for inputting the next letter as compared to the Qwerty keyboard, an input speed may decrease. As the portable terminal is compact-sized, even when a Qwerty keyboard is provided, the size of the Qwerty keyboard should be made smaller in proportion to the size of the terminal, so that it may still have a problem in an outer appearance or when it is used.
In the Morse communication method which may have a certain restriction in its use, there is a method for transmitting a letter converted into a Morse code using an intermittent time difference at contact points by using a Morse key with two electrical signals consisting of a dot and a dash having a length three times of the dot. It is possible to easily input a Korean, English or a special letter with one hand by adapting the above method to a keypad. In this case, the number of keypads used for inputting letters may decrease. However, the number of the key pressing actions significantly increases, so that a lot of work is needed for inputting one letter. In addition, it is needed to memorize all of the Morse codes corresponding to each letter.