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Activity 2.1 Boolean Logic

Introduction

Computers aren’t just for arithmetic calculations; they can also make decisions based on certain conditions. This ability to make decisions allows programs to handle different outcomes. Let’s explore a few everyday scenarios where a computer might need to make decisions:

In each of these examples, the computer is evaluating a question that can be answered with “yes” or “no”, or more precisely, true or false . In programming, we use something called a boolean to represent these two values: true and false.

What is a Boolean?

In C#, the bool data type is used to store values that can be either true or false. This makes it perfect for logical expressions, which are questions or conditions that the computer can evaluate.

Example

bool isRaining = false;
bool hasUmbrella = true;

In this example, isRaining is set to false because it’s not raining, while hasUmbrella is set to true because you have an umbrella.

Boolean Logic

The study of how logical expressions are formed and evaluated is called boolean logic. In programming, these logical expressions are constructed using operators and values, and they always result in either true or false. Let’s revisit our earlier scenarios to see how they can be expressed as boolean logic:

Just as math has arithmetic operators (like +, -, *, /), C# has operators specifically for boolean logic. These operators allow you to create logical expressions that the computer can evaluate. There are several types of operators:

Equality Operators

Equality ==Result
100 == 100 true
100 == 99 false
"abc" == "abc" true
"ABC" == "abc" false
true == true true
true == false false
Inequality !=Result
100 != 100 false
100 != 99 true
"abc" != "abc" false
"ABC" != "abc" true
true != true false
true != false true

Comparison Operators

Greater/Less than > < Result
100 > 100 false
100 > 99 true
0 < 10 true
0 < -1 false
Greater/Less than or equal >= <= Result
100 >= 100 true
10 >= 99 true
0 <= 0 true
0 <= -1 false

Boolean Logical Operators

There are two important operators in this category that are not listed: logical AND, and logical OR. We will cover these in subsequent lessons.

Logical Negation (NOT) ! Result
!true false
!false true
!(100 > 100) true

Examples of Boolean Expressions

Let’s look at some examples of boolean expressions in C#:

int age = 18;
bool isOldEnough = age >= 18;

In this example, the expression age >= 18 checks if the age is greater than or equal to 18. If the condition is true, isOldEnough is set to true; otherwise, it will be set to false.

bool isEqual = (1000 == 1000);

Here, we are checking if 1000 is equal to 1000. Since this is obviously true, isEqual is assigned the value true.

Conclusion

Boolean logic is essential for enabling computers to make decisions. By using boolean values (true or false) and operators, we can write programs that evaluate conditions and respond accordingly. We’ll dive deeper into boolean logic as we continue, exploring how it can be combined with control flow statements like if statements to create more complex decision-making structures.

Skills to Practice

Instructions

Setup

  1. Create a new C# console application. Name the project 2.1 Boolean Logic.
  2. Click Create.

Code

// Initialize variables
string name = "Mr. Mortimer";
int age = 30;
double bankAccount = 150.00;
bool isATeacher = true;
bool isAMillionaire = false;

// Assign boolean expressions to variables
bool isMyNameMortimer = name == "Mr. Mortimer";
bool isOldEnoughToDrive = age >= 16;
bool canBuyDodgeChallenger = bankAccount > 31000;
bool isSeniorCitizen = age >= 65;

Console.WriteLine("-Name Checks-");
Console.WriteLine($"Is my name Mr. Mortimer? {isMyNameMortimer}");
Console.WriteLine($"Is my name Mr. Mertens? {name == "Mr. Mertens"}");
Console.WriteLine($"My name is not Mr. Merriman: {name != "Mr. Merriman"}");

Console.WriteLine("\n-Age-Related Checks-");
Console.WriteLine($"Am I old enough to drive? {isOldEnoughToDrive}");
bool isOldEnoughToRentCar = age >= 25;
Console.WriteLine($"Am I old enough to rent a car? {isOldEnoughToRentCar}");
Console.WriteLine($"Am I eligible for a senior citizen discount? {isSeniorCitizen}");

Console.WriteLine("-Bank Account Checks-");
Console.WriteLine($"Do I have enough to buy a Dodge Challenger? {canBuyDodgeChallenger}");
bool hasPositiveBalance = bankAccount > 0;
Console.WriteLine($"Do I have a positive bank balance? {hasPositiveBalance}");

Console.WriteLine("\n-Boolean Checks-");
Console.WriteLine($"{name} is a teacher: {isATeacher}");
Console.WriteLine($"{name} is a millionaire: {isAMillionaire}");
bool isNotMillionaire = !isAMillionaire;
Console.WriteLine($"So, {name} isn't a millionaire? {isNotMillionaire}");

// Bonus: logical AND && and logical OR || (Covered in lesson 2.4)
Console.WriteLine("\n-Logical Operator Examples-");
bool canDriveAndBuyCar = isOldEnoughToDrive && canBuyDodgeChallenger;
Console.WriteLine($"Am I old enough to drive AND have enough to buy a Dodge Challenger? {canDriveAndBuyCar}");
bool canDriveOrBuyCar = isOldEnoughToDrive || canBuyDodgeChallenger;
Console.WriteLine($"Am I old enough to drive OR have enough to buy a Dodge Challenger? {canDriveOrBuyCar}");

Debug

-Name Checks-
Is my name Mr. Mortimer? True
Is my name Mr. Mertens? False
My name is not Mr. Merriman: True

-Age-Related Checks-
Am I old enough to drive? True
Am I old enough to rent a car? True
Am I eligible for a senior citizen discount? False

-Bank Account Checks-
Do I have enough to buy a Dodge Challenger? False
Do I have a positive bank balance? True

-Boolean Checks-
Mr. Mortimer is a teacher: True
Mr. Mortimer is a millionaire: False
So, Mr. Mortimer isn't a millionaire? True

-Logical Operator Examples-
Am I old enough to drive AND have enough to buy a Dodge Challenger? False
Am I old enough to drive OR have enough to buy a Dodge Challenger? True

Tips, Tricks, and Reflection

-This demo is just the beginning. Over the next few activities, you’ll see how powerful Boolean expressions can be in decision-making.