Evolution toward Distributed Databases
If we start with the hardware framework, we see that the first-generation technology was characterized by vacuum-tube hardware.
Languages that were developed during this period were designed to facilitate the generation of object code, the binary language that operates directly on the machine. These "code assembly" languages became very popular and added to the mystique of computing by requiring the programmer to learn a very cryptic and unreadable language.
It is interesting to note that until very recently, assembly languages were still used to write operating-system and database software.
Second-generation systems were characterized by transistors. This generation of systems gave rise to the first procedural languages that relied on high-level instructions that did not directly manipulate the computer's registers. This was the beginning of a trend toward "high-level" languages that could take care of all of the low-level machine operations, freeing the programmers to concentrate on the overall programming.
The third generation of computing hardware was characterized by the integrated circuit (IC), and heralded the introduction of computer languages that could be called user friendly.
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Fourth-generation hardware has been characterized by Very Large Scale Integration (VLSI) of processors, and the languages have become even friendlier and easier to program. Fourth-generation languages such as Oracle PL/SQL have taken care of all the low-level programming, leaving it to the programmer to concentrate on high-level program implementations. This is the environment in which Oracle began implementation of distributed-database computing.