The Korean EUC code set consists of two main character groups:
The Hangul code set includes Hangul and Hanja (Chinese) characters. One Hangul character can comprise several consonants and vowels. However, most Hangul words can be expressed in Hanja. Each Hanja character has its own meaning and is thus more specific than Hangul.
The current Korean standard code set, KSC5601, contains 8224 Hangul, Hanja, and special characters. To comply with the Korean standard Extended UNIX Code (EUC), this code set is assigned to CS1 of the EUC.
Input of characters can be accomplished through:
The XK_Hangul key invokes Hangul mode, which must be used to enter Hangul characters. Once Hangul mode is invoked, the KIM composes incoming consonants and vowels according to Hangul composition rules. A Hangul character is composed of a consonant followed by a vowel. A final consonant is optional. If incoming characters violate the construct rule, a warning beep is sounded.
There are about 1500 special characters in the standard code set. These characters must be entered with the Code Input function of the KIM. The Code Input key invokes the Code Input function. When the Code Input function is invoked, the code point for a desired character can be entered in the Code Input auxiliary window.
The XK_Hangul_Hanja key invokes the Hanja mode. Hanja characters can only be converted from the appropriate Hangul character. There are two modes for Hangul-to-Hanja Conversion (HHC): single-candidate and multi-candidate. In this context, a candidate is a selection of possible character choices.
In single-candidate mode, the candidates are displayed one by one on the command line. In multi-candidate mode, up to ten candidates at a time are displayed in an auxiliary window.
When the Hanja conversion mode is employed, any Hangul character can be converted into Hanja when the Conversion key is pressed. Similarly, any Hanja word can be converted to the appropriate Hangul word.
Hanja can also be entered with the Code Input function in the same manner used for entering Hangul.
To allow for these conversions, the following special keys appear on the 106-key Korean keyboard.
| Special Korean Keys | ||
| Key Function | Keysym | Description of Function |
| Hangul/English toggle key | XK_Hangul | Toggles between Hangul and English modes |
| Hanja toggle key | XK_Hangul_Hanja | Toggles Hanja mode on and off |
| Code Input key | XK_Hangul_ Codeinput | Invokes the Code Input function, which allows characters to be entered by their code points |
| HHC All-Candidate key | XK_Hangul_ MultipleCandidate | Invokes the multi-candidate mode |
| HHC Conversion key | XK_Hangul_ Conversion | Invokes the single-candidate mode and also scrolls forward through the candidates in both single-candidate and multi-candidate modes |
| HHC Non-Conversion key | XK_Hangul_ NonConversion | Scrolls backwards through the candidates |
Understanding the ISO Code Sets in AIX Kernel Extensions and Device Support Programming Concepts.