## Unresolved External Symbol Error in Visual Studio: What is it and How do I Fix it?

Unresolved External Symbol: Understanding and Resolving Visual Studio Error

When encountering the "unresolved external symbol" error in Visual Studio, it can be perplexing to decipher its significance. But by examining the error message and its context, we can uncover the underlying issue. Let's delve into the causes and solutions for this common error.

Defining vs. Declaring Functions

In C programming, functions must be both declared and defined. A declaration specifies a function's signature, indicating its name, arguments, and return type. A definition, on the other hand, provides the implementation of the function, detailing its behavior.

Unresolved External Symbol Error

Visual Studio displays the "unresolved external symbol" error when a function is declared in the code, but its definition is missing or not accessible. The message typically lists the unresolved symbol along with the referenced function where it's used.

Potential Causes

The most common causes for an unresolved external symbol error include:

• Declaring a function but forgetting to define it in the corresponding .cpp file.
• Using a library or DLL that contains the function declaration, but the actual definition is not included or linked properly.
• Incorrectly defining a standalone function without the class selector (e.g., A::) when it's a member function of a class.

Resolving the Issue

To resolve the error, follow these steps:

1. Verify that the function is properly defined in its corresponding .cpp file.
2. Ensure that the necessary library or DLL containing the function definition is included and linked to your project.
3. Check if the function is declared as a member of a class and that the definition includes the correct class selector (e.g., A::).

By systematically addressing these potential causes, you can effectively resolve the "unresolved external symbol" error and continue developing your code seamlessly.

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