This question asks who is regarded as the father of the modern computer. Let's weigh each candidate's actual historical contribution against that specific phrasing.
- Charles Babbage: Babbage designed mechanical calculating devices, including the Analytical Engine, in the 19th century. He is widely credited as the father of the computer for conceiving a general-purpose mechanical computing device, but his machines were mechanical, not electronic, and predate the modern, theoretical foundations of computation by roughly a century. This makes him a poor fit for the phrase "modern computer" specifically.
- Alan Turing: In 1936, Turing formalized the concept of computation itself through the Turing Machine, an abstract model capable of simulating any algorithm. This theoretical framework underlies how every electronic digital computer since has been understood to compute, which is precisely why the term "modern computer" points to him rather than to earlier mechanical pioneers.
- John von Neumann: Von Neumann is credited with the stored-program architecture, describing how a computer's memory holds both instructions and data. This is an important structural design contribution, but it builds on the computational theory Turing had already established rather than originating the foundational concept of computation itself.
- Bill Gates: Gates co-founded Microsoft and was central to the personal computer software industry, but his contributions are commercial and software-based from the late 20th century onward, not foundational to computing theory or hardware architecture.
Because the question specifically asks about the modern computer rather than the computer in the broadest historical sense, the answer points to the person whose theoretical work defines how modern computers compute.
Therefore, the correct answer is Alan Turing.