Four-corner method
The four-corner method or four-corner system (simplified Chinese: 四角号码检字法; traditional Chinese: 四角號碼檢字法; pinyin: sì jiǎo hàomǎ jiǎnzì fǎ; lit. 'four corner code lookup-character method') is a character-input method used for encoding Chinese characters into either a computer or a manual typewriter, using four or five numerical digits per character.