Due to the inherent differences between and , the Hong Kong Government recognized the need for a standardized set of ''proprietary'' characters that would allow for the streamlining of electronic communication; at the time, the Big5 Chinese encoding scheme did not contain a vast majority of these characters .
The Government Chinese Character Set or GCCS was thus developed by the government. The character set consists of Chinese characters commonly used in Hong Kong. Some characters are -specific, while some are alternative forms of characters. The set is not well-organised and the characters are not closely examined.
Subsequently, the HKSCS-1999 was developed. Following its acceptance, newer revisions were released in 2001 and in 2004 , totalling 4,941 characters.
The HKSCS is encoded in Big5 and ISO 10646. Starting from HKSCS-2004, all characters using to Private Use Area section of Unicode are remapped, with many of them reassigned to Extension B Block or Supplementary Ideographic Plane Compatibility Block. However, to preserve compatibility with programs that generated PUA code points, the allocated code points are reserved, and no new characters will be mapped to .
In Microsoft Windows 98, NT 4.0, 2000, XP, HKSCS support can be enabled using Microsoft's patch. In Microsoft's implementation, application using code page 950 automatically uses a hidden code page 951 table. The table supports all code points in HKSCS-2001, except for the compatibility code points specified by the standard. In addition, the MingLiU font is altered using Microsoft's patch. This patch is known to create conflicts in applications such as Microsoft Office, or any application using fonts supporting simplified Chinese characters . If the target environment contains custom font mapped to the code points affected by Microsoft's patch, the custom fonts can undo Microsoft's patch. Furthermore, the patch breaks EUDC Editor supplied with the affected versions of Windows.
According to Microsoft, HKSCS-2004 characters will only be supported in Unicode 4.1 or later encoding. A utility is available to convert HKSCS and PUA-encoded characters to Unicode 4.1 version .
Software for entering HKSCS characters can be found in Hong Kong government's Digital 21 site.
In Windows Vista, HKSCS-2004 is fully supported, and characters can be displayed using MingLiU_HKSCS, MingLiU_HKSCS-ExtB fonts. All characters are assigned standard, non-PUA codepoints.
Entering HKSCS characters can be done in Windows Vista. For earlier versions of the OS, it requires the use of Microsoft's patch, or using Digital 21's utility.
HKSCS support was added to glibc in 2000, but it has not been updated since then.
For freedesktop.org setup, ''AR PL ShanHeiSun Uni'' font fully supports HKSCS-2004 since 0.1-0.dot.1, with latest revision of HKSCS-2004 supported in version 0.1.20060903-1.
Mac OS X 10.0-10.2 supports HKSCS-1999. 10.3-10.4 supports HKSCS-2001.
Mozilla 1.5 and above supports HKSCS, with HKSCS-2004 support added into Gecko 1.8.1 code base. Unlike the above mentioned patch, Mozilla uses its own code page table.
3.x-based applications only support characters mapped to code points FFFF or lower. In QT4, characters outside BMP are supported via surrogates.
GNOME supports HKSCS characters in Unicode ranges, except those mapped to the Basic Multilingual Plane compatibility block.