Characters that are generated using a keyboard's "ALT" key are special characters and symbols not found on the keyboard. These characters include accented letters, special mathematical symbols, foreign characters, currency symbols and punctuation marks.
The ALT key numeric codes are the keystroke values of the special characters and symbols in the Microsoft Windows operating system. For example, the numeric code for generating the degree symbol is 0176.
A keyboard must be equipped with a separate numeric keypad to use ALT key numeric codes. To insert the degree symbol into a word processor, the ALT key is pressed and held down while keying in 0176. The ALT key is then released and the degree symbol is automatically generated.
Other ALT key characters include 0162, 0128 and 0169, which are keystroke values for the cent sign, euro currency and copyright symbol, respectively.