In the digital age, you’ll most likely come across the term “alphanumeric characters.” You can run into it when creating a password for an account on a website or while learning computer programming. Wherever it is, you might ask yourself: What are alphanumeric characters? Well, you have come to the right place.

This article serves as a guide to alphanumeric characters: from the alphanumeric definition to how the characters are used in real life, it will teach you everything you need to know. Keep on reading.

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What are Alphanumeric Characters?

Let’s kick off this guide with what alphanumeric characters mean. Alphanumeric characters are the numbers 0-9 and letters A-Z (both uppercase and lowercase). An alphanumeric example are the characters a, H, 0, 5 and k.

These characters are contrasted to non-alphanumeric ones, which are anything other than letters and numbers. Examples of non-alphanumeric numbers include &, $, @, -, %, *, and empty space. In special cases, like when creating a password, some non-alphanumeric characters are considered alphanumeric, making them special characters in the set.

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Alphanumeric Characters List

There are scenarios where you need to enter or recognize alphanumeric characters. The table below is a good reference of the alphanumeric character set:

AlphabetA, a, B, b, C, c, D, d, E, e, F, f, G, g, H, h, I, i, J, j, K, k, L, l, M, m, N, n, O, o, P, p, Q, q, R, r, S, s, T, t, U, u, V, v, W, w, X, x, Y, y, Z, z
Numbers0, 1, 2, 3, 4, 5, 6, 7, 8, 9
Symbols@ (“at” sign), $ (dollar sign), # (pound sign)
Special characters* (asterisk), & (ampersand), { } (braces), (comma), [ ] (brackets), – (hyphen), = (equal sign), . (period), () (parenthesis), ; (semicolon), + (plus sign), or single quotation mark), ‘ (apostrophe), / (slash)

As you can see, you can find all of these letters, numbers and symbols on your keyboard or smartphone keypad. You should be able to recognize them since they look familiar from everyday usage.

How Alphanumeric Characters Are Useful in Real Life

Alphanumeric characters are used in several real-life scenarios. Here are a few examples.

Creating a Username

Many websites ask you to create a unique username as your identifier on the site. You can also use the username when signing into the website. So how do they make sure that each user creates a unique name? Through alphanumeric characters. 

If your name is John Smith and you find that someone has already taken it, just add a number. An alphanumeric example of a username would be something like “John01” or “JOhnSm1th”. As you can see, when you incorporate numbers into your name, you can create a one-of-kind identifier.

In many cases, some websites allow you to sign up or sign in using your email address. And the interesting thing is that your email address is also alphanumeric.

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Creating a Strong Password

Another alphanumeric character example is the creation of strong passwords. When registering on a website or app, many of them won’t allow you to enter a weak password. After all, they don’t want hackers to gain access to your account. An account breach compromises your personal data and poses a security risk for the site and app owners.

Without requiring the addition of alphanumeric characters, people might create straightforward passwords. The most common ones include birthdays and names of spouses, children and pets. A password like “fido” would be much easier to hack than “fido2021$”. Just the addition of numbers and symbols can still make it easy to remember but extremely strong.

Creating File Names

You also use alphanumeric characters to create file names, although some special characters aren’t allowed. If you are trying to create two files with the same name in one location on your computer, the operating system (OS) won’t allow you to use the same name for both. It will either ask you if you want to replace the existing file or create a duplicate.

When you create a file without naming it, the OS will probably call it “New File.” And if you tried to create another file in that same location, it will be named “New File (1)” and so on. So if you want to create two files with similar names in the exact location, just make it more alphanumeric by including numbers and special characters. That way, the OS will accept it.

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Passenger Seats

Airplanes, busses, ships and other vehicles used for passenger transportation usually have their seat numbers assigned as alphanumeric. For example, a seat number might be 27C, where the number represents the row, and the letter is the column. Mapping seats this way allows you to identify your seat quickly.

One interesting thing you’ll notice on many airlines is that one row will have seats HJK. You might ask yourself, “Wait a minute. Where did the letter ‘I’ go in the middle of ‘H’ and ‘J’?” It was intentionally removed to avoid human misinterpretation. When the human brain sees a mix of alphanumeric characters, it can easily conflate the ones that look similar. This misinterpretation is especially problematic for dyslexic people. So the letter ‘I’ is omitted so it wouldn’t be mistaken for the number 1.

Vehicle Numbers

When assigning vehicle numbers, manufacturers also use alphanumeric characters. You might also find that they don’t use the letters I, O and Q because people might misinterpret them as 1 and 0.

Alphanumeric Codes

Alphanumeric codes are ways of representing alphanumeric data. Many of these codes are heavily used today, playing a crucial role in helping us communicate with each other. They also help us interface with computers and other devices in the form of a keyboard, mouse, gamepad, camera, touchscreen, microphone and other input-output devices.

There are several alphanumeric codes around. Here are three examples of the most popular ones.

1. Binary Code

Binary code is extremely popular with computer programmers. A computer doesn’t understand alphanumeric characters the way a human does. However, a computer does understand binary code. It is a system that uses a combination of 0s and 1s to represent characters, numbers and symbols. So for coders to get the machine to understand their instructions, they have to be in binary code.

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So, if you want to write the letter B in binary code, it would be something like 01000010, and the number 2 is 10. Binary is also called machine code, but if you want to be a coder and are worried that binary won’t be fun to program in, don’t worry. You’ll most likely do your programming language using high-level, human-readable languages like Python, JavaScript, C# or Java.

When using these languages, the computer’s processor will convert your high-level code into machine code. Then, it will execute those instructions without you ever having to write a single piece of binary code.

2. American Standard-Code for Information Interchange (ASCII)

ASCII, which is pronounced “as-kee,” is another popular alphanumeric code. The standard ASCII character sets are made up of 128 characters. These include numbers, letters, symbols, special characters and control characters (e.g., space, ESC, backspace, and delete). Each one is assigned a number from 0 to 127. For example, the letter H in ASCII is 72, and the number 5 is 53.

So why is ASCII important? Well, it is how almost all your text editors save your documents. You might type J-a-n-e in Notepad, and you’ll see “Jane” on your computer monitor. However, when encoding the text, the program will store it as 74 97 110 101. And as long as another text editor uses ASCII, it will be able to decode the text file, allowing you to read it.

3. Morse Code

Morse code is a way of encoding a limited set of characters with two signals known as dots and dashes. Samuel Morse invented the code in 1837. It is an old form of coded communication, where you tap dots and dashes while pausing for a specific duration between characters and words. 

Perhaps the most famous use of Morse code is communicating SOS, a well-known signal for distress. The letter ‘S’ is denoted by three dots and ‘O’ by three dashes. Therefore SOS will be three dots, three dashes and three dots in Morse code.

Wrapping Up

Alphanumeric characters aren’t hard to understand. After all, the standard alphanumeric character set just consists of the 26 letters of the alphabet and numbers 0-9. Furthermore, these characters also have important uses, from creating a username and password on a social media platform to giving vehicles’ numbers. They’re even used to form codes that foster human and machine communication.

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