Boolean logic is a key concept in any programming language, whether you’re creating a video game with C++, developing the next best app in Swift, searching through relational databases in SQL, or working with big data in Python. In this article, we’ll cover what Boolean logic is, how it works, and how to build your own Boolean expressions.

What is Boolean logic?

Boolean logic is a type of algebra in which results are calculated as either TRUE or FALSE (known as truth values or truth variables). Instead of using arithmetic operators like addition, subtraction, and multiplication, Boolean logic utilizes three basic logical operators: AND, OR, and NOT.

TRUE and FALSE: There can only be two

Behind Boolean logic are two very simple words: TRUE and FALSE.

Note that a Boolean TRUE or FALSE is very different from typing the strings “True” and “False” into your code. In fact, programming languages put these two Boolean values into their own object type separate from integers, strings, and floating-point numbers. But while there can be practically infinite possibilities for a numerical or string value in programming, there are only two possible Boolean values: TRUE and FALSE.

How does this work? Boolean logic looks at a reported relationship between things and determines whether the relationship holds. For example, let’s take the equation:

2 + 2 = 4

Here, we have two parts, 2 + 2 and 4, and we’re reporting that those two parts are equal to each other. Is that right? Yes it is, so the Boolean result of this would be TRUE. In this example, the combination of the two parts 2 + 2 and 4, together with the relationship (= equals), is called a Boolean expression.

Let’s look at another Boolean expression:

10 – 4 = 5

Here, we’re reporting that 4 subtracted from 10 is the same as 5. Is that right? Of course not, and that’s why this Boolean expression would return a value of FALSE.

Building Boolean expressions

Keep in mind that Boolean logic only works when an expression can be TRUE or FALSE. For example, the expression 3 + 8 isn’t a Boolean expression because it’s not being compared or related to something else. But the expression 3 + 8 = 10 is a Boolean expression because we can now evaluate each side and see if the reported relationship between them is TRUE or FALSE (in this case, it’s FALSE).

We can build Boolean expressions with all kinds of data, including variables. For example, let’s suppose that we’ve assigned these values to variables x and y somewhere in our code:

x is 7
y is 3

Now, we can build Boolean expressions using our variables:

Boolean expressions can also determine whether two strings are identical. Just remember that most programming languages are case-sensitive.

There are many other ways to build Boolean expressions, depending on the programming language. For example, you could use a Boolean expression to determine whether a number is contained within a list in Python or whether a text string is within a SQL database table.

Boolean operators

Now that you understand the basics of Boolean expressions, let’s look at another key aspect of Boolean logic: Boolean operators. There are three basic Boolean operators, AND, OR, and NOT.

To better understand how Boolean operators work, let’s suppose for a moment that we’re in an ice cream shop. Say we’re going to put together a two-scoop sundae with different flavors. But I’m a bit of a picky eater, so I may not accept every sundae combination that I get. We can use Boolean expressions and Boolean operators to figure out whether I’ll eat a sundae or not.

AND

The Boolean AND operator is used to confirm that two or more Boolean expressions are all true.

For example, in my sundae, I want the first flavor to be chocolate and the second flavor to be vanilla. We could turn this into a Boolean expression with an AND operator that looks something like this:

Flavor_1 = Chocolate AND Flavor_2 = Vanilla

This means that both the first flavor must be chocolate and the second flavor must be vanilla. Otherwise, I won’t eat the sundae.

We could organize this situation into a table of possibilities like this:

Tables like this are used in Boolean logic all the time. They’re called truth tables, and we can put one together for our sundae example. If something meets my picky sundae flavor conditions, then it’s TRUE. If not, then it’s FALSE.

Here’s how the table above would look like in truth table form:

OR

The Boolean OR operator checks that either one condition or another is true.

For example, if I wanted either the first flavor to be strawberry or the second flavor to be mango, then the Boolean expression would be:

Flavor_1 = Strawberry OR Flavor_2 = Mango

We could organize the possibilities as:

And the truth table would look like this:

Note that the OR operator returns TRUE if one of the two Boolean expressions is true, but also when both expressions are true. For this reason, this OR operator is also known as an inclusive OR operator. Alternatively, there’s also the XOR (exclusive or) operator, which only returns TRUE when one of the two expressions is true.

NOT

The Boolean NOT operator is different from AND and OR as it only takes one argument. It tests if a value is FALSE or not. Put another way, it changes TRUE values to FALSE and FALSE values to TRUE.  For example, I hate Rum Raisin and absolutely will not eat anything with Rum Raisin in it. How might that look in table form?

The truth table looks like this:

You can combine Boolean expressions to express my sundae preference when Rum Raisin is involved like so:

NOT (Flavor_1 = Rum Raisin OR Flavor_2 = Rum Raisin)

The OR clause within the parentheses will return TRUE for anything with Rum Raisin in it. Applying the NOT to it will change the OR expression’s value from TRUE to FALSE and vice versa. Much like operators in arithmetic, Boolean operators have an order of precedence: elements within a parentheses are addressed first, then the NOT operator, AND, and lastly OR. Our new truth table looks like this:

Applying your Boolean logic

So, what’s next after learning the basics of Boolean logic?

Boolean logic is critical to creating code that helps your program quickly make decisions about data and inputs, so try putting your Boolean knowledge to use with an online programming course. And if you’re not sure which course to try next, take a look at our developer career paths. We’ll help you focus on the best skills you need to succeed in your desired role.

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If you wanted to learn how to speak a new language, like Spanish, it wouldn’t make sense to pick up a few vocab words and then decide to start learning Mandarin, too. It’d be confusing, right?

Programming languages are a different story, according to Alex Kuntz, Curriculum Manager at Codecademy. “You certainly don’t need to master one language before moving onto the next,” Alex says. In fact, it’s standard for programmers to toggle between different languages throughout their careers.

Pretty much all programming languages share core features, like variables, conditionals, loops, lists, and functions, Alex says. Once you have those fundamentals down, then you can absolutely dabble in another language — or several languages — and you’ll see how they utilize those same tasks, he says. Another big difference between spoken language and programming? You don’t have to memorize everything when you code — it’s very common to look up code snippets as you need them.

Don’t stress about learning everything there is to know about a specific programming language. “Instead focus on learning concepts, because those concepts will show up in almost every programming language,” Alex says. “And as long as you have a good grasp on the concepts in one language, it is relatively easy to master those concepts in a different language.”

Here are a few common instances when you would want to learn another programming language.

You’re starting a new project

One of the obvious reasons why you’d learn another programming language is if you’re tasked with a project that requires a specific language. Let’s say your employer wants you to create a mobile app: You’d need to know Swift to build iOS apps or React for Android. Or, perhaps you need a more efficient way to automate tasks at work? In that case, you might want to use Ruby, JavaScript, or Python.

Bottom line: Deciding what programming language you should learn boils down to your goal. For example, if you want to build a website, you might want to learn JavaScript, or if you’re working with data, it might make more sense to learn something like SQL or Python. Once you’re familiar with programming generally, you can dive into more advanced and specific features for the language that’s most relevant to you, Alex says.

You’re changing careers (or thinking about it)

If you have your mind set on changing careers to a specific role in tech, then figuring out what languages you need to learn is relatively straightforward. For instance, if you want to become a data scientist, you’d want to learn SQL and Python. An aspiring web developer, on the other hand, would be better suited to learn HTML/CSS and JavaScript.

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Be sure to read job descriptions carefully, because they’ll typically list the technical skills and languages that are required for the role. For example, it might say something like, “Knowledge of Java required: JavaScript preferred.” In that case, JavaScript is a desired skill, but not a necessity to be considered for the position.

If you already have a job and are looking for ways to leverage a promotion, adding a language to your tech stack is a smart way to upskill.

Think: What technical skills would give you a leg up in your current role? Where are the gaps in your team’s knowledge, and how could you fill them? How can learning a new language streamline your company’s workflow so it’s more efficient?

Once you determine what language would be best suited for your needs, here’s how to ask your employer to pay for professional development.

Good to know: Keep track of the projects that you work on as you learn; they’ll come in handy if you need to present a case study to advocate for your promotion. Check out our Portfolio Projects for more advanced projects that will help you showcase your skills.

You’re just curious

There’s a good chance you’ve heard the adage “programmers are perpetual students” before. That basically means that there’s always something new to learn. And with hundreds of programming languages out there, nobody knows absolutely everything there is to know about coding — that’s what makes it so rewarding and fun.

If you’ve hit a wall with a particular language or course, you might need to shake things up and start learning a new language to stay engaged. It may just be a matter of learning enough to try a project or code challenge to get more hands-on practice.

“It’s typical to stick with one language until you have those fundamentals down,” Alex says. “Then it’s a great idea to look at another language — or multiple other languages — to see how those languages handle those common features.”

If you’re taking a Codecademy course, keep in mind that they’re self-paced. In addition to trying different courses altogether, you can always adjust your long-term goal or amp up your weekly learning targets. (On the flip side, if you need to take a break and come back to a course, that’s okay — you won’t lose your progress.)

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