John von Neumann helped to create this model as an example of a general-purpose computing machine. By treating the instructions in the same way as the data, the machine could easily change the instructions. In other words the machine was reprogrammable.

Because the machine did not distinguish between instructions and data, it allowed a program to modify or replicate a program. These features are exploited by computer viruses when they add copies of themselves to existing program code.

The problem of unauthorized code replication can be addressed by the use of memory protection support, and in particular virtual memory architectures.

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