Dart, like all programming languages, provides basic data types that act as building blocks for coding. In this lesson, we will delve into the core data types in Dart: int, double, bool, String, and null. We will learn how to use these data types to represent numbers, boolean values, text data, and the absence of value, respectively.

In Dart, numerical data types are used to represent numbers. Specifically, this section focuses on int and double. The int data type is used to represent whole integer numbers, while the double data type is used to represent decimal numbers — numbers with decimal points.

The largest value an int can store is 9223372036854775807, which is $2^{63} - 1$. The smallest value it can hold is -9223372036854775808, which is $-2^{63}$. Here's an example of using the int data type:

Dart
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1int daysInWeek = 7;
2print(daysInWeek);  // This will print: 7
3
4int maximalInteger = 9223372036854775807;
5print(maximalInteger);  // This will print: 9223372036854775807
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7int tooBigInteger = 9223372036854775808; // Oops! Error, the number is too large

Next, let's explore the double data type. The double data type is used when dealing with numbers that have decimal points, also known as floating-point numbers. A double can hold up to 15 decimal digits of precision. Consider the following example:

Dart
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1double pi = 3.141592653589793;
2print(pi);  // This will print: 3.141592653589793

The next item in the agenda is the bool data type.

The bool data type in Dart can hold one of two possible values: true or false. This particular data type is extensively used in logical expressions and decision-making structures. Here's a simple example:

Dart
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1bool isEarthRound = true;
2print(isEarthRound);  // This will print: true
3
4bool isEarthFlat = false;
5print(isEarthFlat); // This will print: false

Dart treats String as a basic data type, using it to store a sequence of characters — or simply put, text. The string is always encased within either double or single quotes.

Dart
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1String welcome = "Welcome to Dart!";
2print(welcome); // This will print: Welcome to Dart!

In Dart, the String data type is immutable. Once a String value is created, its content cannot be changed; however, the variable referencing the String can be reassigned to point to a different String value.

As we conclude this journey, we discuss a very special value: the null value. null signifies "no value", "nothing", or "unknown". It is crucial to note that it's not equivalent to an empty string ("") or 0.

Here's an example of how to assign null to a variable:

Dart
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1String unknown = null;
2print(unknown);  // This will print: null

Bravo! You've successfully navigated Dart's basic data types. You are now equipped to use int and double for numerical computations, bool for decision-making, String to handle text, and null to represent an unknown value.

Although we've covered a substantial amount of information, further practice awaits. This subsequent practice aims to solidify your understanding. Therefore, prepare for the exercises designed to test your newly acquired knowledge!