To enter into a computer the information required to begin a session.
進入，注冊，登錄：往計算機內(nèi)輸入開始一個程序的信息
To enter into a computer the command to end a session.
退出，注銷：往計算機內(nèi)輸入結束一個程序的信息
(informal)very easy
(非正式)易如反掌
go through the procedures to begin use of a computer system, which includes establishing the identity of the user
進入（系統(tǒng)），注冊，登錄
go through the procedures to conclude use of a computer system
退出（系統(tǒng)），注銷