Wikipedia
Hunminjeongeum (lit. The Correct/Proper Sounds for the Instruction of the People) is a document describing an entirely new and native script for the Korean language. The script was initially named after the publication, but later came to be known as hangul. It was created so that the common people illiterate in hanja could accurately and easily read and write the Korean language. It was announced in Volume 102 of the Annals of King Sejong, and its formal supposed publication date, October 9, 1446, is now Hangul Day in South Korea. The Annals place its invention to the 25th year of Sejong's reign, corresponding to 1443-1444.
Hunminjeongeum is a Korean language word processor designed by Samsung Electronics. Its filename extension is .gul. It was first released in 1992 as South Korea's first fully corporate-sponsored word processor.