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A little Smalltalk
The next important step in the development of object oriented languages was Smalltalk. Living on the West coast of the USA, Alan Kay was in the middle of the hardware revolution but he also knew about Simula - a strange Norwegian import. Putting the two together allowed him to dream about computers that were simple enough for children to use. To realise his dream he joined the newly formed Xerox Palo Alto Research Centre (PARC) and set up the Learning Research Group. The final result of the work was far from the concept of a computer suitable for children but it was an easy and powerful to use programming environment.
The early versions of Smalltalk - Smalltalk 72 and 76 - were working towards the educational objective but after Kay left the research group in 1981 the emphasis of the project shifted. The group was renamed the Software Concepts Group and Smalltalk 80 was revamped as a `serious language'. Other members of the group who made significant contributions were Adele Goldberg, David Robinson, Larry Tesler, Dan Ingalls and Peter Deutch.
Smalltalk was the first object-oriented language to dispense with the trappings of old ways of doing things. That is, Smalltalk was nothing but objects and new programs were created by modifying existing objects - the so-called base classes. Although this experimental work continued though the 70's the product was only refined enough to have an impact in the early 80's and it took until the mid to late 80's for the hardware to be powerful enough to make the approach practical.
Also invented at PARC during the same period were overlapping windows, icons and mode-less operation. In fact you could say that the Smalltalk project produced the first graphical environment. If you think that this honour should go to the MAC then it is worth saying that a visit by Steve Jobs (one of the founders of the Apple Corporation and co-designer of the Apple II) to PARC resulted in Apple hiring Larry Tesler (in 1981) to work on the LISA project, the forerunner of the MAC. Interestingly the MAC only implemented the Smalltalk environment - windows, icons and mouse - and not the object oriented language itself.
Objects and other languages
The object-oriented approach became so popular in the late 80's that it was obvious that the more traditional languages would have to incorporate the new features. Bjarne Stroustrup at AT&T extended C to create C++. There were other object-oriented extensions to C but, being at AT&T, Stroustrup had the necessary authority to ensure that C++ became the standard.
Bjarne Stroustrup, born 1950
Other significant object-oriented extensions to existing languages were the two object Pascals - one from Microsoft and one from Borland. These aren't compatible but they are at least similar in approach. Fortran, Lisp and Forth also included object-oriented extensions, but rather less seriously than C++ and languages such as Ada and Modula 2 included some aspects of the object oriented method. You could say every language wanted to be object oriented but not all had the flexibility to do the job convincingly.