ATOK is an IME with roots from KTIS (Kana-Kanji Transfer Input System) come with JS-WORD, the Japanese word processor software for PC-100 in 1983,[2] but it now supports a variety of platforms including macOS, Windows, Android, and iOS.

[5] Linux, OS/2, Palm OS, Pocket PC, and Windows CE are no longer supported.

[6] KTIS and ATOK was originally a component of JustSystems' word processor software.

[7] In DOS era, ATOK was spreading with Ichitaro despite competition from VJE, Matsutake, and some other software.

MS-IME 97 contained notable improvements, and was bundled with a new retail box of Windows 95 and Office 97.