On Windows: To insert a character using its numeric code, press and hold down Alt while typing the numbers on the numeric keypad. Code starting with 0 is interpreted as Unicode character; otherwise, below 256 is interpreted in Windows codepage.
At present on Unix systems, there are three ways of entering letters with accents directly from the keyboard.
Solaris: 使用 Sun 键盘。先按空格键右侧的 Compose 键,然后输入第一个和第二个修饰符。