Structured Programming (1972)

The ACM has made the book Structured Programming available for free. One of the most interesting parts of the book is what it has to say about objects as implemented in Simula:

> A procedure which is capable of giving rise to block instances which survive its call will be known as a class; and the instances will be known as objects of that class. A class may be declared, with or without parameters, in exactly the same way as a procedure...

That original idea of objects is very similar in spirit to a closure. It is amazing to have an article on object-orientation inside the book about structured programming. The ideas are so old, yet keep getting rediscovered.