KS keyboard was designed to use it on the English teletypewriter machine in 1969 by the South Korean Government. However, Korean government adopted it as a standard keyboard for computer in 1982.

Following defects are found with the KS keyboard and APH keyboard has removed all of these defects of KS keyboard.

1. Difficult to memorize positions of each key: Though, it has separation of consonants (located on the left hand side) and vowels (on the right hand side), it did not follow the scientific logics of Hangul. Remedy by APHK: Not only it separated consonants (on left) from vowels (on right), but also arranged by sequence of location of organs where the sound created, but also clustered together by similar sound values and shapes of alphabets, so that one can easily remember the location of keys.
2. Input speed is very slow in comparison to other keyboard arrays: It is slower than Gong, Byung Woo keyboard (about 20%). It is much slower than APH keyboard (minimum of 50% in serial input, and a few hundred % slower than simultaneous input system). Remedy by APHK keyboard: Arranged by careful study of Hangul frequencies. More frequently used ones on home rows and inside ones. More usage of thumbs for the bottom row.
3. Visual confusion by frequent movement of trailing consonants and initial consonants by up and down movements: As the computer can not determine whether the consonants can be used as the initial consonants or the trailing consonants until the following keys are inputted. If the following alphabet is a vowel, it moves to the next position to become an initial consonant, otherwise, it will stay as a trailing consonant. Remedy by APHK: It has separated initial consonants and trailing consonants on the keyboard itself.
4. Unnecessary internal re-programming to assemble for a syllabic character: KS keyboard can only input Hangul alphabet serially as in English input, and Korean Hangul have to output assembled syllabic character, it is necessary to assemble it internally with Hangul automata to find the appropriate code number for assembled (or semi-assembled) character to output. Remedy by APHK: In the input stage, APHK system pushes keys of assembled syllabic character simultaneously, and output character is painted by its shape according to the given rules.
5. Too many unnecessary character codes: Currently there are 12,106 code points(11,172 codes for Hangul Syllables, 240 for Hangul Jamo and 94 for Compatible Hangul Jamo) are assigned to Hangul in ISO/IEC 60646, which is the second largest code points after Chinese Hanzi. Remedy by APHK: Assigning only 45 Jamo (17 Initial consonant Jamo, 11 Median Jamo and 17 Trailing consonant Jamo), treating all other Jamo as glyphs, it can create millions of syllabic characters. Only what it requires is development of the algorism how to place these different glyphs within given spaces.
6. It cannot process any Korean documents produced before 1933, and cannot process foreign languages, due to the elimination of four archaic Hangul Jamo from keyboard: namely, Pan-siot, Yet-ieung, Yeorin-hieut and Are-A. KS keyboard doesn’t have these four alphabets. Remedy by APHK: It has all four old Hangul alphabets, assigned on the top of similar looking and sounded alphabets, accessible by shift keys. Pan-siot on the top of ㅅ, Yet-ieung on the top of ㅇ, Yeorin-hieut on the top of ㅎ, and Are-A on the top of ㅏ.
7. Excessive use of left hand: KS keyboard has consonants on the left hand and vowels on the right hand. Korean Hangul syllabic character is consisted of either consonant(s) and vowel(s), or initial consonant(s), vowel(s) and trailing consonant(s). In the case of later, left hand fingers have to use more than right hand fingers. The ratio between left hand finger usage and right hand usage is 56.82:42.18, which means left hand use 34.7% more than right hand. Most of ordinary people are right handed and using left hand fingers excessively causes more frequent fatigue on left hand and main reason of carpal tunnel syndrome on that hand. APHK keyboard has assigned on both hands evenly.
8. Confusion of one vowel(ㅠ) located on the right hand side: KS keyboard has consonants on the left hand side and vowels on the right. There is one exception. Vowel ㅠ is located on the right hand side. This causes not only visual confusion, but also our autonomous nerve system confuses between vowels and consonants. Also it creates confusions on the ergonomically designed keyboard which usually separates right and left hand apart. Those who do not know much about the Korean Hangul misunderstand this ㅠ vowel as a consonants. APH keyboard removed such confusion by completely separating initial consonants, vowels and trailing consonants and assigned completely on different locations.
9. Benign neglect of phonetic value of Korean Hangul. When Hangul was proclaimed as Hoonmin Jungeum (Teaching of People with Correct Sound - an original name of Hangul) in 1446 by King Sejong, he said, where there are natural sounds (phonetics) in nature, there should be writing system which is equivalent to it. Therefore, Hangul is invented to scribe all the sounds in the nature, including all the phonetics of languages. However, KS keyboard is a hindrance to this proclamation. APH keyboard has removed all of these hindrances by making it a more flexible to create more than several million phonetic syllabifies
10. KS keyboard can not input simultaneously, though it was invented over 5 centuries ago to write syllabic characters and perfectly good writing system for modern computers for simultaneous input. The reason why it can not input simultaneously is that it mimics English system, which has to depend on other system such as shorthand machine to input alphabets for fast simultaneous input. Remedy by APH keyboard is that it has separate initial consonants and trailing consonants, so that it can type simultaneously as in the case of stenographic shorthand machine.
11. Same finger use: As KS keyboard does not have trailing consonants separate from the initial consonants, it has to type with too many same fingers. For example to type 학교, with KS system, you have to type ㅎ ㅏ ㄱ ㄱ ㅛ, which requires to strike ㄱ twice. There are too many such words which require same finger use consecutively. APH keyboard doesn’t have such consecutive same finger use, as it has separate trailing consonants.
12. Too many shift keys use. Since KS keyboard input is only serial input of Hangul Jamo, just like English input system, some words have double and triple meanings without separation of syllable ending. For instance, one type ㅇ ㅏ ㄱ ㄱ ㅣ ㄷ ㅏ, it could mean 악기다, which means ‘this is a musical instrument, or 아끼다, which means ‘one is sparing’, or ‘one is try to save’. Therefore, to separate the syllable ending KS keyboard need five double consonants (ㄲ,ㄸ,ㅆ,ㅉ,ㅃ), placed on the top of each respective single consonants. These five consonants and two vowels are used with shift keys and their usage is 2.09% of the total. Since shift key is used with small fingers and requires some time to move there, typing is three times slower than without it. Since the typing rhythm is broken, it is prone to the miss-typing. APH keyboard do not have anything like it, except the archaic Jamo, on the upper level.
13. Impossible to input foreign language with KS keyboard. Korean language belongs to Ural Altaic language group, and therefore, other languages are not easy to spell with KS keyboard. Due to the fact that there are no archaic Jamo and not possible to mix Jamos freely to create certain non-Korean sound. It can not apply to other languages. APH keyboard is designed to mix them freely, including with archaic Hangul Jamo.