Key input device and character input method using directional keys

A key input device is provided for inputting digits/letters/characters/symbols by a keypad and a character input method for the key input device. In the key input device, a mode key is pressed to select one of a plurality of key matrixes for a corresponding mode, which is displayed on a display. A first directional key is used for inter-cell movement in the displayed key matrix and a second directional key is used to select an intended digit/letter/character/symbol within a cell. In the character input method, a mode with a unique key matrix is set by pressing a mode key. An intended cell is moved to within the key matrix by pressing a first directional key. An intended digit/letter/character/symbol is selected in the cell by pressing a second directional key. The selected digit/letter/character/symbol is displayed on a display.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a key structure, a key input device, and a character input method in an apparatus for inputting digits and characters using a keypad, and in particular, to a method for representing all characters available in a known 3×4 key input scheme by use of a small number of keys.

2. Description of the Related Art

Many key input devices and character input methods have been developed in the field of mobile radio terminals in order to easily represent intended characters, while minimizing the area of the key input devices along with the trend of reducing the size of the terminal. They include the known 3×4 key input scheme, a 2-way slide key input scheme, and a 4-way key input scheme. The latter two schemes were suggested as alternatives for the 3×4 key input scheme.

Due to the minimum space requirement of a keypad, the 3×4 key input scheme was an obstacle to miniaturization of mobile radio terminals. “Minimum space requirement” refers to a minimum space required for precise selection of an intended key and isolation of the key from its adjacent keys on a keypad when a user manipulates the keypad. That is, for a terminal to recognize a key pressed by the user, the key should be spaced from its adjacent keys by a distance enough to prevent the key pressing from influencing the adjacent keys. The 2-way slide key input scheme and the 4-way key input scheme appear to be favorable candidates for the replacement of the 3×4 key input scheme in that they contribute to the reduction of the minimum space requirement of the keypad. Despite this advantage, their key input mechanisms cause a user inconvenience and time delay in key input. Particularly, a longer time is required to enter Korean alphabet characters (Hangul).

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a key input device and a character input method, which minimize the space of a keypad, solving the conventional problems encountered in key input.

It is another object of the present invention to provide a key input scheme which allows intended characters to be easily input in a minimized key input device and a character input method for the key input device.

It is a further object of the present invention to provide a key input scheme for readily adding intended characters in a key input device and a character input method.

The foregoing and other objects are achieved by a key input device for inputting digits/letters/characters/symbols by a keypad and a character input method for the key input device. In the key input device, a mode key is pressed to select one of a plurality of key matrixes for a corresponding mode, which is displayed on a display. A first directional key is used for inter-cell movement in the displayed key matrix and a second directional key is used to select an intended digit/letter/character/symbol within a cell. In the character input method, a mode with a unique key matrix is set by pressing a mode key. An intended cell is moved to within the key matrix by pressing a first directional key. An intended digit/letter/character/symbol is selected in the cell by pressing a second directional key. The selected digit/letter/character/symbol is displayed on a display.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described hereinbelow with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

A “key matrix” used herein indicates an arrangement of keys preset to represent characters in a corresponding language mode according to a 4-directional (4-D) key structure of the present invention in a mobile radio terminal. It is also to be noted that blocks of characters in the key matrix are termed cells. All characters available in the 3×4 key input scheme are represented by the use of two 4-D keys from key matrixes displayed on a display.

A key input device and a character input method will be described in two embodiments shown inFIGS. 1to6and inFIGS. 7to17B, respectively according to usage of 4-D keys. A detailed description will first be made of an embodiment of the key input device and the character input method using 4-D keys shown inFIGS. 1to6.

FIG. 1is a schematic view of a keypad according to a first embodiment of the present invention. The keypad includes a 4-D key A12, a mode key16, and a 4-D key B14.FIG. 2is a block diagram of a mobile radio terminal according to the first embodiment of the present invention. Referring toFIG. 2, the mobile radio terminal is comprised of a controller10, a keypad20, and a display18. The keypad20includes the 4-D key A12, the 4-D key B14, and the mode key16. According to how many times the mode key16is pressed, the controller10displays a key matrix in a corresponding mode on the display18. In the embodiment of the present invention, a digit mode, a Korean mode, an English capital mode, an English small mode, and a special mode are sequentially set as the number of pressings of the mode key16increases, by way of example.

FIG. 3Aillustrates function options that can be set by use of the 4-D key A12according to the first embodiment of the present invention. Before the mode key16is pressed, the 4-D key A12acts to invoke the functions of a menu, confirm, a phone book, and mail. When the 4-D key A12is pressed without inputting the mode key16, the controller10displays a function option on the display18according to the pressed direction of the 4-D key A12, as shown in FIG.3A.

FIG. 3Billustrates a key matrix for a digit mode according to the first embodiment of the present invention. When the mode key16is pressed once, the controller10displays the key matrix specific to the digit mode on the display18as shown in FIG.3B.

FIG. 3Cillustrates a key matrix for a Korean mode according to the first embodiment of the present invention. When the mode key16is pressed twice, the controller10displays the key matrix specific to the Korean mode on the display18as shown in FIG.3C.

FIG. 3Dillustrates a key matrix for an English capital mode according to the first embodiment of the present invention. When the mode key16is pressed three times, the controller10displays the key matrix specific to the English capital mode on the display18as shown in FIG.3D.

FIG. 3Eillustrates a key matrix for an English small mode according to the first embodiment of the present invention. When the mode key16is pressed four times, the controller10displays the key matrix specific to the English small mode on the display18as shown in FIG.3E.

FIG. 3Fillustrates a key matrix for a special mode according to the first embodiment of the present invention. When the mode key16is pressed five times, the controller10displays the key matrix specific to the special mode on the display18as shown in FIG.3F.

As shown inFIGS. 3Bto3F, each key matrix is divided into three to six blocks on the display18. Alphabet letters/characters and numerals are grouped into at least three cells in the key matrix. Each cell is assigned to elements of the key matrix in a predetermined rule inFIGS. 3Bto3F for better understanding of the present invention.

Referring toFIGS. 3Bto3F, the 4-D key A12is used for inter-cell movement and the 4-D key B14is used to select an intended digit/alphabet/symbol within a cell in each key matrix displayed on the display18. In the Korean mode, vowels are selected relying on the scheme of “Cheon-Ji-In (●-—-|)” as shown below in Table 1. According to the “CHEON-JI-IN” scheme, Korean vowels are produced by the combination of three Korean alphabet characters, namely, (●-—-|), which are minimum elements to make the Korean vowel characters. Thus, although Korean vowels can be produced by adding two Korean characters together, Korean vowels can also be produced by only one Korean character or by adding three Korean characters together.

FIG. 4illustrates a key structure and a character input method according to the present invention. As shown inFIG. 4, as the number of pressings of the mode key increases, the mobile radio terminal is sequentially set to the digit mode, the Korean mode, the English capital mode, the English small mode, and the special mode in this order and their corresponding key matrixes are displayed on the display18. The 4-D key A moves between cells and the 4-D key B selects a digit/letter/character/symbol within a cell. To move to a cell that includes an intended digit/letter/character/symbol, a user presses the 4-D key A up, down, left, or right. After a cursor is placed in the intended cell, the user presses the 4-D key B up, down, left, or right to select the intended digit/letter/character/symbol. The selected digit/letter/character/symbol is displayed in an upper part of the display18. Then, to go to the next intended cell, the user presses the 4-D key A in a corresponding direction.

An example of inputting digits and Korean alphabet characters according to the above-described key structure and character input method will be described referring toFIGS. 5 and 6.

FIG. 5is a view illustrating a telephone number input method according to the first embodiment of the present invention. For entering a telephone number “012-345-6789”, the user presses the mode key16once to enter the digit mode. Then, the controller10ofFIG. 2displays the key matrix for the digit mode on the display18. As shown inFIG. 5, the cursor is placed over digit “8” at the center of a center cell Sb2in the key matrix. The 4-D key A12and the 4-D key B14are denoted by A and B, respectively in the key input procedure presented in the lower part of the FIG.5. Arrows indicate the pressed directions of the 4-D keys A and B. To enter digit “0”, the user presses ▾ of the 4-D key B14and the controller10displays digit “0” on the display18. Then to enter digit “1”, the user moves the cursor to a first cell Sb1by pressingof the 4-D key A12. Since the cursor is positioned at the center of the first cell Sb1, the user presses ▴ of the 4-D key B14to select digit “1” and then the controller10displays digit “1” after digit “0” on the display18. After one digit/letter/character/symbol is entered, the cursor returns to the home position. In the same manner, the other digits “3”, “4”, “5”, “6”, “7”, “8”, and “9” are entered.

FIG. 6illustrates a Korean alphabet character input method according to the embodiment of the present invention. For “”, the user presses the mode key16twice to set the Korean mode and the controller10displays the key matrix for the Korean mode on the display18. As shown inFIG. 6, the cursor is positioned at the center of a center cell Sc2in the key matrix. The 4-D key A12and the 4-D key B14are denoted by A and B, respectively in the key input procedure presented in the lower part of the FIG.6. Arrows indicate the pressed directions of the 4-D keys A and B. To enter consonant “”, the cursor must move from the home position to a third cell Sc3. To do so, the user pressesof the 4-D key A12. He selects consonant “” by pressingof the 4-D key B14. Upon recognition of selection of “”, the controller10displays “” on the display18. For vowel “”, “|”, “•”, and “|” are entered by pressing ▴ & ▾, ●, and ▴ & ▾ of the 4-D key A12. The controller10displays the resulting Korean alphabet “” after “” on the display18. The other Korean alphabets “”, “|”, “”, “”, and “” are entered in the same manner.

A second embodiment of the key input device and the character input method using 4-D keys will now be described with reference toFIGS. 7to17B.

FIG. 7illustrates the second embodiment of the key input device according to the present invention. The key input device includes a keypad20with the 4-D key A12, the 4-D key B14, and the mode key16, and keys “SEND”22, “CLEAR”24, and “END”26formed on a sidewall of the mobile radio terminal. The display18displays a key matrix30with cells28, individually labeled C11, C12, C13, C21, C22, C23, C31, C32, C33.

The controller10displays a key matrix30for a corresponding mode on the display18according to the number of pressings of the mode key16. In this embodiment, the digit mode, the Korean mode, the English capital mode, and the English small mode are sequentially set as the number of pressings of the mode key16increases, by way of example.

FIGS. 8Ato9illustrate function keys that can be set by use of the two 4-D keys in combination without pressing the mode key16.

FIG. 8Aillustrates the display that displays function options set by utilizing the two 4-D keys in combination according to the second embodiment of the present invention. A function option list32is displayed on the display18so that the user may select an intended function option utilizing the directional navigation keys. The function option list32may include 25 keys that can be set by utilizing the two 4-D keys in combination and 5 keys that can be set by utilizing the 4-D key B14alone, thus a total of 30 functions. These function keys can be set as keys related with a phone book, mail, alarm, and etc., or hot keys.

FIG. 8Billustrates the keypad including the two 4-D keys that are used in combination to select function options. To identify the keys and directions, the directions of the 4-D key A are labeled with capital alphabet letters and those of the 4-D key B, with small alphabet letters in the second embodiment of the present invention.

FIG. 8Cis a table showing 30 combinations of the two 4-D keys to set function options according to the second embodiment of the present invention.

FIG. 8Dis a table illustrating the function options F1to F30versus combinations of the two 4-D keys according to the second embodiment of the present invention.

FIG. 9is a flowchart illustrating a method of selecting function options utilizing the two 4-D keys according to the second embodiment of the present invention. Referring toFIG. 9, the controller10determines whether the user has pressed the mode key16in step100and sets the digit mode, the Korean mode, the English capital mode, or the English small mode according to how many times the mode key16was pressed in step102. If the mode key16is not pressed in step100, the controller10determines whether the 4-D key A has been pressed in step104. If the 4-D key A was pressed, the controller10determines in which direction it was pressed in step108. On the other hand, if the 4-D key A was not pressed in step104, the controller10determines whether the 4-D key B has been pressed in step106.

In step108, the controller10proceeds in the pressed direction of the 4-D key A in the keypad20of FIG.8B. For example, if the 4-D key A is pressed up, the controller10is directed to A and determines whether the 4-D key B has been pressed in step110. If the 4-D key B was pressed, one of functions F6to F10is input according to the pressed direction of the 4-D key B in step124. On the other hand, if the 4-D key B was not pressed in step110, the controller10goes to step120. In step120, the controller10waits for two seconds and then returns to step100. In the same manner, the other functions are input according to the pressed directions of the 4-D keys A and B.

If the controller10determines that only the 4-D key B has been pressed in steps104and106, it inputs one of functions F1to F5according to the pressed direction of the 4-D key B in step122.

FIGS. 10Ato11illustrate input of digits by combining the two 4-D keys in the digit mode when the mode key16is pressed once.

FIG. 10Aillustrates the display18with a key matrix for the digit mode according to the second embodiment of the present invention. The key matrix30with cells of digits and symbols C11, C12, C13is displayed on the display18. A digit/symbol can be selected by using the two 4-D keys in combination.

FIG. 10Billustrates the keypad including the two 4-D keys which are used in combination to input digits in the digit mode according to the second embodiment of the present invention. To identify the keys and directions, the directions of the 4-D key A are labeled with capital alphabet letters and those of the 4-D key B, with small alphabet letters in the second embodiment of the present invention.

FIG. 10Cis a table showing 30 combinations of the two 4-D keys to set digits/symbols according to the second embodiment of the present invention.

FIG. 10Dis a table illustrating the digits/symbols versus combinations of the two 4-D keys in the digit mode according to the second embodiment of the present invention. Key combinations by which no digits/symbols are set can be reserved for later needs.

FIG. 11is a flowchart illustrating a method of inputting the two 4-D keys to select digits/symbols in the digit mode according to the second embodiment of the present invention. Referring toFIG. 11, the controller10sets the digit mode when the mode key16is pressed once in step102of FIG.9. In step200ofFIG. 11, the controller10provides an initial display for the digit mode as shown in FIG.10A. In step202, the controller10determines whether the 4-D key A has been pressed. If the 4-D key A was pressed, the controller10determines in which direction it was pressed in step206. On the other hand, if the 4-D key A was not pressed in step202, the controller10determines whether the 4-D key B has been pressed in step204.

In step206, the controller10proceeds in the pressed direction of the 4-D key A in the keypad20of FIG.10B. For example, if the4-D key A is pressed left, the controller10is directed to B and determines whether the 4-D key B has been pressed in step208. If the 4-D key B was pressed, one of digits 1 to 5 is input according to the pressed direction of the 4-D key B in step214. On the other hand, if the 4-D key B was not pressed in step208, the controller10goes to step218. In step218, the controller10waits for two seconds and then returns to step200. In the same manner, the other digits/symbols are input according to the pressed directions of the 4-D keys A and B.

If the controller10determines that only the4-D key B has been pressed in steps202and204, it inputs one of 0 and 6 to 9 according to the pressed direction of the 4-D key B in step212.

FIGS. 12Ato13illustrate input of English small letters by combining the two 4-D keys in the English small mode when the mode key16is pressed four times.

FIG. 12Aillustrates the display18with a key matrix for the English small mode according to the second embodiment of the present invention. The key matrix30with cells of small alphabet letters C11, C12, C21, C22, C23, C32is displayed on the display18. A small alphabet letter can be selected by using the two 4-D keys in combination. Frequently used vowels a, e, i, o, u are collected in the center cell C22so as to increase convenience in inputting keys and minimize unnecessary key inputs.

FIG. 12Billustrates the keypad including the two 4-D keys which are used in combination to input small alphabet letter in the English small mode according to the second embodiment of the present invention. To identify the keys and directions, the directions of the 4-D key A are labeled with capital alphabets and those of the 4-D key B, with small alphabets in the second embodiment of the present invention.

FIG. 12Cis a table showing30combinations of the two4-D keys to set small alphabet letters in the English small mode according to the second embodiment of the present invention.

FIG. 12Dis a table illustrating the English small alphabet letters versus combinations of the two 4-D keys in the English small mode according to the second embodiment of the present invention. Small alphabet letter “x” is input when the center of the 4-D key A is pressed, thereby minimizing the number of unnecessary key inputs.

FIG. 13is a flowchart illustrating a method of selecting English small alphabet letters using the two 4-D keys in the English small mode according to the second embodiment of the present invention. Referring toFIG. 13, the controller10sets the English small mode when the mode key16is pressed four times in step102of FIG.9. In step300ofFIG. 13, the controller10provides an initial display for the English small mode as shown in FIG.12A. In step302, the controller10determines whether the 4-D key A has been pressed. If the 4-D key A was pressed, the controller10determines in which direction it was pressed in step306. On the other hand, if the 4-D key A was not pressed in step302, the controller10determines whether the 4-D key B has been pressed in step304.

In step306, the controller10proceeds in the pressed direction of the 4-D key A in the keypad20of FIG.12B. For example, if the 4-D key A is pressed up, the controller10is directed to A and determines whether the 4-D key B has been pressed in step308. If the 4-D key B was pressed, one of h, j, l, m, k is input according to the pressed direction of the 4-D key B in step320. On the other hand, if the 4-D key B was not pressed in step308, the controller10goes to step328. In step328, the controller10waits for two seconds and then returns to step300. In the same manner, the other small alphabet letters are input according to the directions of the 4-D keys A and B.

If the controller10determines that only the 4-D key B has been pressed in steps302and304, it inputs one of o, e, i, u, a according to the pressed direction of the 4-D key B in step318.

FIGS. 14Ato15illustrate input of English capital letters by combining the two 4-D keys in the English capital mode when the mode key16is pressed three times.

FIG. 14Aillustrates the display18with a key matrix for the English capital mode according to the second embodiment of the present invention. The key matrix30with cells of capital alphabet letters C11, C12, C21, C22, C23, C32is displayed on the display18. An English capital letter can be selected by using the two 4-D keys in combination. Frequently used vowels A, E, I, O, U are collected in the center cell C22so as to increase convenience in inputting keys and minimize unnecessary key inputs.

FIG. 14Billustrates the keypad including the two 4-D keys which are used in combination to input English capital letters in the English capital mode according to the second embodiment of the present invention. To identify the keys and directions, the directions of the 4-D key A are labeled with capital alphabet letters and those of the 4-D key B, with small alphabet letters in the second embodiment of the present invention.

FIG. 14Cis a table showing 30 combinations of the two 4-D keys to set English capital letters in the English capital mode according to the second embodiment of the present invention.

FIG. 14Dis a table illustrating the English capital letters versus combinations of the two 4-D keys in the English capital mode according to the second embodiment of the present invention. Capital alphabet letter “X” is input when the center of the 4-D key A is pressed so as to minimize the number of unnecessary key inputs.

FIG. 15is a flowchart illustrating a method of selecting English capital letters using the two 4-D keys in the English capital mode according to the second embodiment of the present invention. Referring toFIG. 15, the controller10sets the English capital mode when the mode key16is pressed three times in step102of FIG.9. In step400ofFIG. 15, the controller10provides an initial display for the English capital mode as shown in FIG.14A. In step402, the controller10determines whether the 4-D key A has been pressed. If the 4-D key A was pressed, the controller10determines in which direction it was pressed in step406. On the other hand, if the 4-D key A was not pressed in step402, the controller10determines whether the 4-D key B has been pressed in step404.

In step406, the controller10proceeds in the pressed direction of the 4-D key A in the keypad20of FIG.14B. For example, if the 4-D key A is pressed up, the controller10is directed to A and determines whether the 4-D key B has been pressed in step408. If the 4-D key B was pressed, one of H, J, L, M, K is input according to the pressed direction of the 4-D key B in step420. On the other hand, if the 4-D key B was not pressed in step408, the controller10goes to step428. In step428, the controller10waits for two seconds and then returns to step400. Upon input of the 4-D key A in the direction E in step406, the controller10inputs capital “X” as shown in FIG.14D. In the same manner, the other English capital letters are input according to the directions of the 4-D keys A and B.

If the controller10determines that only the 4-D key B has been pressed in steps402and404, it inputs one of O, E, I, U, A according to the pressed direction of the 4-D key B in step418.

FIGS. 16Ato17B illustrate input of Korean alphabet characters by combining the two 4-D keys in the Korean mode when the mode key16is pressed twice.

FIG. 16Aillustrates the display18with a key matrix for the Korean mode according to the second embodiment of the present invention. The key matrix30with cells of Korean alphabet characters C11, C12, C13, C21is displayed on the display18. A Korean alphabet character can be selected by using the two 4-D keys in combination. Double consonants “,,,,” are collected in the cell C21and successive two pressings of the 4-D key A in the direction B moves the cursor to the cell C21so as to increase key input convenience and minimize unnecessary key inputs.

FIG. 16Billustrates the keypad including the two 4-D keys which are used in combination to input Korean alphabet characters in the Korean mode according to the second embodiment of the present invention. To identify the keys and directions, the directions of the 4-D key A are labeled with English capital alphabet letters and those of the 4-D key B, with English small alphabet letters in the second embodiment of the present invention.

FIG. 16Cis a table showing 30 combinations of the two 4-D keys to set Korean alphabet characters in the Korean mode according to the second embodiment of the present invention. In the Korean mode, vowels are selected using the 4-D key B 14, relying on the “Cheon-Ji-In” scheme. In this scheme, vowels “|” and “—” are produced by continuously pressing the 4-D key B14up and down (a & d directions) and left and right (b & c directions), respectively and vowel “•” is input by pressing the 4-D key B14in the direction e.

FIG. 16Dis a table illustrating the Korean alphabet characters versus combinations of the two 4-D keys in the Korean mode according to the second embodiment of the present invention.

FIG. 17Ais a flowchart illustrating a method of selecting Korean consonants using the two 4-D keys in the Korean mode according to the second embodiment of the present invention. Referring toFIG. 17A, the controller10sets the Korean mode when the mode key16is pressed twice in step102of FIG.9. In step500ofFIG. 17A, the controller10provides an initial display for the Korean mode as shown in FIG.17A. In step502, the controller10determines whether the 4-D key A has been pressed. If the 4-D key A was pressed, the controller10determines in which direction it was pressed in step506. On the other hand, if the 4-D key A was not pressed in step502, the controller10determines whether the 4-D key B has been pressed in step504.

In step506, the controller10proceeds in the pressed direction of the 4-D key A in the keypad20of FIG.16B. For example, if the 4-D key A is pressed left, the controller10is directed to B and determines how many times the 4-D key A has been pressed in the direction of B. If the 4-D key A was pressed twice in the direction B, the controller10inputs one of the double consonants “,,,,” according to the pressed direction of the 4-D key B in step518. If the 4-D key A was pressed once in the direction B in step512, the controller10inputs one of consonants “,,,,” according to the pressed direction of the 4-D key B in step520. On the other hand, if the 4-D key B was not pressed in step512, the controller10goes to step524. In step524, the controller10waits for two seconds and then returns to step500. Upon input of the 4-D key B in the directions A, B, and C in step506, the controller10inputs corresponding characters as shown in FIG.17A and goes to step526of FIG.17B. In the same manner, the other Korean alphabet characters are input according to the directions of the 4-D keys A and B.

If the controller10determines that only the 4-D key B has been pressed in steps502and504, it inputs one of, ∈,,according to the direction of the 4-D key B in step516.

FIG. 17Bis a flowchart illustrating a method of selecting Korean vowels using the two 4-D keys in the Korean mode after the procedure shown inFIG. 17Aaccording to the second embodiment of the present invention. Referring toFIG. 17B, the controller10determines whether the 4-D key B has been pressed in step526, after a particular Korean consonant was input. If the 4-D key B was pressed, the controller10determines in which direction it was pressed in steps528,532,538,542, and544. On the other hand, if the 4-D key B was not pressed in step526, the controller10returns to step502of FIG.17A.

If the 4-D key A is pressed in the direction a in step528, the controller10determines whether the 4-D key A is pressed again in the direction d in step530. If it is, the controller10inputs the vowel “|” in step531and returns to step500to stand by for input of a new Korean alphabet character. If the 4-D key A is not pressed in the direction d in step530, the controller10inputsin step516of FIG.17A.

If the 4-D key A is pressed in the direction b in step532, the controller10determines whether the 4-D key A is pressed again in the direction c in step534. If it is, the controller10inputs the vowel “—” in step536and returns to step500to stand by for input of a new Korean alphabet character. If the 4-D key A is not pressed in the direction c in step534, the controller10inputsin step516of FIG.17A.

If the 4-D key A is pressed in the direction e in step538, the controller10inputs the vowel “•” in step540and returns to step500to stand by for input of a new Korean alphabet character. If the 4-D key A is not pressed in the direction e in step538, the controller10determines whether the 4-D key A is pressed in the directions c and d in steps542and544.

If the 4-D key A is pressed in the direction c in step542, the controller10inputsin step516of FIG.17A. If the 4-D key A is pressed in the direction d in step544, the controller10inputsin step516of FIG.17A.

As described above, the present invention provides a key structure that occupies a minimum area and a user-friendly interface. Therefore, the present invention is useful for implementation as a character input device and method in a subminiature mobile radio terminal or a device requiring a very small keypad. In addition, the number of key inputs can be remarkably reduced because a cursor for 4-D keys automatically returns to its home position after one digit/letter/character/symbol is input and frequently used characters (e.g., vowels in the English modes) and/or symbols are collected in one cell. Key matrixes for different modes are preset with the mode key and each key matrix is divided into a plurality of cells, so that the key matrixes are readily expandable and individual characters can be easily added to the cells in each key matrix.