C++ FAQ Celebrating Twenty-One Years of the C++ FAQ!!!
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Section 11:
[11.1] What's the deal with destructors?

A destructor gives an object its last rites.

Destructors are used to release any resources allocated by the object. E.g., class Lock might lock a semaphore, and the destructor will release that semaphore. The most common example is when the constructor uses new, and the destructor uses delete.

Destructors are a "prepare to die" member function. They are often abbreviated "dtor".