Why Do I Get the LNK2019 Error: \"unresolved external symbol _main\" in C ?

Addressing the LNK2019: unresolved external symbol error in C

In the realm of C programming, the dreaded LNK2019 error can often leave developers perplexed. This error arises when the linker fails to locate an external symbol named _main during the compilation process.

Within the provided code, the implementation of a sequence class raises this error. While the code appears to be modular and type-safe, the fundamental problem lies in the absence of a defined main function elsewhere in the project.

To remedy this error, consider the following steps:

• Define a separate main function in another source file. This function should be the entry point of the program and typically takes the form:

<code class="cpp">int main() {
  // Program logic goes here
  return 0;
}</code>

• Ensure that the main function is declared and defined in the header file and source file, respectively.

In Visual Studio, if you encounter this error even with a defined main function, the following workaround may prove helpful:

1. Navigate to Project -> Properties.
2. Click on Configuration Properties.
3. Expand Linker and select System.
4. Under SubSystem, select Console.

This modification instructs the linker to expect a console application executable.

Once these steps are implemented, the linker should successfully resolve the external symbol reference, allowing the program to compile and execute seamlessly.

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