Who discovered that 20% of the instruction code did 80% of the work?

The correct answer is John Cocke, who is known for his work in computer architecture and compiler design. He is particularly recognized for formulating what is now known as the "80/20 rule" or Pareto principle in the context of instruction code efficiency. This principle suggests that a small proportion of the input (in this case, 20% of the instruction code) is often responsible for a large proportion (80%) of the output or work done by a system. This insight is crucial in both systems design and software development, leading to optimizations that focus on the most impactful parts of a program to enhance performance effectively.

The other individuals listed made significant contributions to computing but are not associated with this particular discovery. Bill Gates is well-known for founding Microsoft and promoting personal computing software. Linus Torvalds is famous for creating the Linux operating system. Alan Turing is celebrated as a pioneer of theoretical computer science and artificial intelligence. While their contributions are pivotal to the field, it was John Cocke who specifically highlighted the relationship between a small part of the codebase and the majority of processing demands in computing.