Boolean expression facts for kids

A Boolean expression is a special kind of question that a computer asks itself. When a computer looks at a Boolean expression, the answer is always either true or false.

Computers use these true/false answers to make decisions. For example, a program might ask, "Is the user's age greater than 18?" If the answer is true, it might show certain content. If it's false, it might show something else.

Most Boolean expressions include at least one variable. A variable is like a placeholder for a value that can change. For example, X > 3 asks if the value of X is greater than 3. This makes the expression useful for many different situations.

What are Boolean Operators?

Boolean operators are special words or symbols that help us combine or change Boolean expressions. The most common ones are:

• AND
• OR
• NOT

Think of them like connectors in a sentence.

The "AND" Operator

The AND operator means that both parts of the expression must be true for the whole expression to be true.

• In some programming languages, "AND" is written as &&.
• For example, if you say "I want a game that is fun AND free", you only get the game if it's both fun and free. If it's fun but costs money, you don't get it.

The "OR" Operator

The OR operator means that at least one part of the expression must be true for the whole expression to be true.

• In some programming languages, "OR" is written as .
• For example, if you say "I want a snack that is sweet OR salty", you'll be happy if it's sweet, or if it's salty, or if it's both! You only won't be happy if it's neither.

The "NOT" Operator

The NOT operator flips the answer of an expression. If something is true, "NOT" makes it false. If something is false, "NOT" makes it true.

• In some programming languages, "NOT" is written as !.
• For example, if the expression "It is raining" is true, then "NOT (It is raining)" would be false.

Other Boolean operators exist too, like XOR (exclusive OR). This means one or the other is true, but not both.

Examples of Boolean Expressions

Let's look at some examples to see how Boolean expressions work:

• The expression 5 > 3 asks, "Is 5 greater than 3?" The answer is true.
• The expression 3 > 5 asks, "Is 3 greater than 5?" The answer is false.

Now let's use variables and operators:

• The expression (X > 3) AND (X < 5) asks, "Is X greater than 3 AND is X less than 5?"

* If X is 4, then (4 > 3) is true, AND (4 < 5) is true. So, the whole expression is true. * If X is 6, then (6 > 3) is true, but (6 < 5) is false. Since both parts are not true, the whole expression is false.

• The expression {{{1}}} asks, "Is X less than or equal to 3 OR is X greater than or equal to 5?"

* If X is 2, then (2 <= 3) is true. So, the whole expression is true (because one part is true). * If X is 4, then (4 <= 3) is false, AND (4 >= 5) is false. So, the whole expression is false.

• The expression NOT ((X > 3) AND (X < 5)) means "It is NOT true that X is between 3 and 5."

* If X is 4, then ((4 > 3) AND (4 < 5)) is true. So, NOT (true) becomes false. This makes sense because 4 is between 3 and 5. * If X is 6, then ((6 > 3) AND (6 < 5)) is false. So, NOT (false) becomes true. This makes sense because 6 is not between 3 and 5.

Boolean expressions are a fundamental part of how computers make decisions and control the flow of programs.