Header Errors LNK2019, LNK1120 - Unresolved Externals

Hello all.

I'm trying to create a simple header and implement it in a cpp file, but I am experiencing the following error messages.

LNK2019 unresolved external symbol _WinMain@16 referenced in function "int __cdecl invoke_main(void)" (?invoke_main@@YAHXZ)
LNK1120 1 unresolved externals

Here is the code for my header.

#include <iostream>

class Cat
{
public:
	Cat(int initialAge);
	~Cat();
	int GetAge() const { return itsAge; }
	void SetAge (int age) { itsAge = age; }
	void Meow() const { std::cout << "Meow.\n"; }
private:
	int itsAge;
};

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Here is the code for the cpp file I am trying to compile.

#include "Cat.h"


Cat::Cat(int initialAge)
{
	itsAge = initialAge;
}

Cat::~Cat()
{
}

int main()
{
	Cat Frisky(5);
	Frisky.Meow();
	std::cout << "Frisky is a cat who is " << Frisky.GetAge() << " years old.\n";
	Frisky.Meow();
	Frisky.SetAge(7);
	std::cout << "Now Frisky is " << Frisky.GetAge() << " years old.\n";
	return 0;
}

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Both have been copied directly from a book, and try as I might I can't see any mistakes in my transcription.

Many thanks in advance!