Origin of Hangul
Ledyard holds that the Koreans adopted five core consonant letters from ’Phags-pa, namely ㄱ "g" , ㄷ "d" , ㅂ "b" , ㅈ "j" , and ㄹ "l" . These were the consonants basic to Chinese phonology, rather than the graphically simplest letters (ㄱ "g" , ㄴ "n" , ㅁ "m" , and ㅅ "s" ) taken as the starting point by the "Haerye." A sixth letter, the null initial ㅇ, was invented by Sejong. The rest of the consonants were developed through featural derivation from these six, essentially as described in the "Haerye"; a resemblance to speech organs was an additional motivating factor in selecting the shapes of both the basic letters and their derivatives.
Sungkyunkwan
The primary written language of Sungkyunkwan was hanja. Although hangul was invented in 1443, it did not become the primary language of study because the literary elite believed that the difficult hanja was more sophisticated. Hangul was invented to solve the widespread illiteracy of the common people at the time, but it was considered a threat by many in the upper class to their status as literary scholars, leading them to resist its implementation. As a result, hanja remained the written language used at Sungkyunkwan requiring anyone who wished to rise to the top levels of the government to be capable of reading and writing the characters.