By the time of his death, how much of Babbage's mechanical computing machines were completed?

Babbage's mechanical computing machines, particularly the Analytical Engine and the Difference Engine, were groundbreaking concepts that laid the foundation for modern computing. However, despite significant work and design, very little of these machines was actually completed during his lifetime.

The Difference Engine, which was intended to compute polynomial functions, saw some progress, with parts being built, but it was never fully operational. The Analytical Engine, a more ambitious project designed for general-purpose computation, existed primarily in the form of sketches and theoretical constructs. Babbage's work encountered numerous technical and financial challenges, as well as a lack of adequate funding and support.

Therefore, stating that only a small portion of his machines was completed aligns with the historical context of Babbage's projects. It reflects the reality that while Babbage made important advancements in the conception and design of computing machinery, the actual physical realization of his ideas was minimal by the time of his death.