To create a character that is not directly mapped to the keyboard, most personal computers can use a function called an alt code to use a combination of keys and create the symbol. This is because there are many more symbols and characters that can be read by the computer than there are keys on a keyboard. On Apple computers, the option key can be used to complete this function.
To use an alt or option key code, the user must hold down the alt key and then input a series of numbers while the computer has a text input box selected, according to Pennsylvania State University. There are many comprehensive lists of alt key code combinations online, but it is also possible to experiment and discover the symbols offline by simply trying different number combinations.
The symbols that can be created using an alt key code vary in function and appearance greatly. People who have keyboards without any accented letters can use alt codes to create letters with different accent marks on them. These codes can also generate symbols that are generally only used in languages other than that spoken where the keyboard was purchased. Alt key codes can generate much more than just letters, however. They can be used to access mathematical operators and symbols that are not present on standard keyboards, as well as different currency symbols and uncommon punctuation marks.