Introduction

In programming, every value has a type. A type tells the computer what kind of data is being stored or used. For example, a value may be a number, text, true/false value, list, object, or some other kind of data.

Programming languages handle these data types in different ways. Some languages check the type of a variable before the program runs, while some languages check the type while the program is running. Based on this behavior, languages are commonly classified as statically typed languages and dynamically typed languages.

Prerequisites Before Learning This Topic

Before understanding statically and dynamically typed languages, students should know the basics of variables and data types. These concepts make type checking easier to understand.

What is Type in Programming?

A type defines the category of data that a value belongs to. It tells the programming language what operations can be performed on that value.

For example, numbers can be added, subtracted, multiplied, and divided. Text values can be joined together, searched, or converted to uppercase or lowercase. Boolean values are used in decision-making conditions.

What is Type Checking?

Type checking is the process of checking whether values and variables are being used according to their correct data types. It helps prevent mistakes such as adding a number to an object, calling a method on the wrong type, or storing text in a variable that should only contain numbers.

The main difference between static typing and dynamic typing is when this checking happens.

What is a Statically Typed Language?

A statically typed language is a programming language where the type of a variable is checked before the program runs, usually during compilation. In many statically typed languages, the programmer must declare the type of a variable when creating it.

If a variable is declared as a number, the language will not allow it to suddenly store text unless a proper conversion is performed. This helps catch many errors early before the program is executed.

Example of Static Typing

In the following example, the variable is declared with a specific type.

int marks = 85;
String name = "Amit";
boolean isPassed = true;

Here, marks is expected to store an integer, name is expected to store text, and isPassed is expected to store a boolean value.

Type Error Example in Static Typing

int marks = 85;
marks = "Excellent";

This would produce an error because marks was declared as an integer, but the new value is text.

What is a Dynamically Typed Language?

A dynamically typed language is a programming language where the type of a variable is checked while the program is running. The programmer usually does not need to declare the type of a variable explicitly.

In dynamically typed languages, a variable can store one type of value at one moment and another type of value later. The language decides the type based on the value assigned to the variable at runtime.

Example of Dynamic Typing

let marks = 85;
marks = "Excellent";
marks = true;

In this example, the same variable marks first stores a number, then a string, and then a boolean value. This is possible in many dynamically typed languages.

Statically Typed vs Dynamically Typed Languages

The following table compares static typing and dynamic typing in a beginner-friendly way.

How Static Typing Works

In static typing, the language checks whether each variable is being used with the correct type before the program runs. This usually happens during the compilation stage.

If the compiler finds a type mismatch, it stops the program from running until the error is fixed. This prevents many mistakes from reaching the final program.

How Dynamic Typing Works

In dynamic typing, the language does not require the type of a variable to be fixed before execution. The type is decided based on the value assigned to the variable at runtime.

This gives flexibility, but it also means that some type-related errors may appear only when that part of the program is executed.

Example: Static Typing and Dynamic Typing Comparison

Let us compare the same idea in two different styles.

Static Typing Style

int age = 20;
age = 25;

// This is not allowed because age is an integer.
// age = "Twenty Five";

Dynamic Typing Style

let age = 20;
age = 25;
age = "Twenty Five";

In the static typing example, the variable is expected to remain an integer. In the dynamic typing example, the same variable can store different types at different times.

Advantages of Statically Typed Languages

Statically typed languages are useful for large, complex, and long-term projects because they provide strong control over data types.

Limitations of Statically Typed Languages

Static typing provides safety, but it can sometimes require more code and feel strict for beginners.

Advantages of Dynamically Typed Languages

Dynamically typed languages are often popular for beginners, scripting, automation, and fast development because they allow quick writing and testing of code.

Limitations of Dynamically Typed Languages

Dynamic typing is flexible, but programmers must test their programs carefully because some errors may not appear until runtime.

Type Inference

Some statically typed languages support type inference. Type inference means the programmer does not always need to write the type manually because the compiler can understand the type from the assigned value.

This makes statically typed code shorter while still keeping type checking before execution.

Type Inference Example

var name = "Amit";
var marks = 85;
var isPassed = true;

In this example, the language can infer that name is text, marks is a number, and isPassed is a boolean value.

Static Typing vs Dynamic Typing vs Type Inference

Students often confuse dynamic typing with type inference. The following table explains the difference clearly.

Static Typing and Dynamic Typing Are Not About Good or Bad

Static typing and dynamic typing are two different design approaches. One is not always better than the other. The best choice depends on the project, team, performance needs, safety requirements, and development speed.

Common Language Examples

The following table shows common examples of statically typed and dynamically typed languages.

Common Mistakes Beginners Make

Beginners often misunderstand static and dynamic typing. The following comparison explains common mistakes and better understanding.

Best Practices for Working with Types

Whether a language is statically typed or dynamically typed, programmers should follow good coding practices to avoid confusion and errors.

Real-world Example: Student Marks

Suppose we are building a student marks system. The marks should be a number because we may need to compare marks, calculate total marks, or find average marks.

Static Typing Example

int marks = 85;

if (marks >= 40) {
    System.out.println("Passed");
} else {
    System.out.println("Failed");
}

Dynamic Typing Example

let marks = 85;

if (marks >= 40) {
    console.log("Passed");
} else {
    console.log("Failed");
}

Both examples can solve the same problem. The difference is how the language handles the type of marks.

Common Interview Questions

Interviewers may ask questions about static and dynamic typing to check whether students understand variables, data types, type checking, and language behavior.

Practice Assignment: Static and Dynamic Typing

This assignment helps students understand how static and dynamic typing work in real programming situations.

Expected Output

After completing this assignment, students should be able to explain the difference between statically typed and dynamically typed languages, identify examples, understand type checking, and choose the right typing approach based on project requirements.

Quick Summary

Statically typed languages check variable types before execution, usually during compilation. This helps catch many errors early and makes code more predictable. Examples include Java, C, C++, C#, Go, Rust, Swift, and Kotlin.

Dynamically typed languages check variable types during execution. They are flexible and often allow faster development, but type-related errors may appear at runtime. Examples include Python, JavaScript, PHP, and Ruby.

Both typing approaches are useful. Static typing is often preferred for large, long-term, safety-focused projects, while dynamic typing is useful for scripting, automation, rapid prototyping, and flexible development.