What is Alphanumeric? – Definition & Characters

Numeric Code

Do you want to learn a secret language? If you do, see if you can decipher this string of numbers. (Look for the answer in the lesson summary.)

83 84 85 68 89 46 67 79 77

Okay, so it isn’t really a secret language. It is the numeric code that computer programmers (and you) can use to create alphanumeric characters in programming. Let’s investigate shall we?

Alphanumeric Defined

Alphanumeric, also known as alphameric, simply refers to the type of Latin and Arabic characters representing the numbers 0 – 9, the letters A – Z (both uppercase and lowercase), and some common symbols such as @ # * and &.

Sites requesting that you create an alphanumeric password are asking us to use a combination of numbers and letters, which creates stronger passwords. We also use alphanumeric keys to create file names, although there are some symbols that are not accepted as part of a file name, such as a slash (/).

That doesn’t seem very secret does it? The ‘secret’ language part comes into play when we start talking about alphanumeric characters in terms of actual computer programming.

Alphanumeric Characters

Since computers (or central processing units, to be specific) use machine language in the form of numbers to communicate, computer programmers need to write their instructions using numbers rather than alphabet characters. To do this, programmers use numeric representations of what humans see as alphabet characters. You’ve probably seen or heard of binary code which uses only 0s and 1s to represent an alphanumeric character. Computer programmers can use a series of 0s and 1s to represent any character they wish. For example, in binary, the letter ‘A’ would be written as 01000001.

Another way computer programmers represent alphanumeric characters is to use ASCII. ASCII stands for American Standard Code for Information Interchange.

Using the ASCII table, a computer programmer can represent the word ‘red’ using the numbers 82 69 68. This is true unless they wanted it in lower case letters, in that case it would be 114 101 100.

Now, you are probably thinking to yourself, ‘I can key those numbers from my keyboard or number pad, and all I get are numbers!’ You would be correct. In order to use those numbers as ASCII code, you need to be using a text-only program such as Notepad (or save a Word document as text only by choosing the plain text option).

Not only do you need to use a text-only file, but you also have to let your application know you want it to convert the code into alphanumeric characters by preceding the ASCII numbers with the ‘Alt’ key and using a numeric keypad such as the one found to the right of most keyboards. (If you are using a Mac, you will use the ‘Option’ key.)

How does this work? If you wanted to represent the letter ‘R’ (upper case), you would hold the ‘Alt’ key and then type the number 82 from the keypad. For ‘r ‘(lower case), you would hold the ‘Alt’ key and then type the number 114 on the keypad. This can be done with every alphanumeric character you want to create. Go ahead and try it! Open a blank file in notepad and press the series of keys described to try to produce ‘R’ and ‘r.’