Which of the following was the key feature of the first computers?

The first computers utilized mechanical parts for calculations, which is a distinguishing feature from modern electronic computers. These early computing machines, such as the Analytical Engine proposed by Charles Babbage, relied on gears, levers, and other mechanical components to perform calculations. This mechanical foundation laid the groundwork for future developments in computing technology, transitioning from mechanical to electronic systems.

In contrast, portability, battery power, and advanced graphical capabilities were not attributes associated with these early computers. During their inception, computers were typically large, immobile, and depended on electrical power instead of batteries. Additionally, they lacked any form of graphical output that we would associate with modern computing devices. Thus, the reliance on mechanical parts is a defining characteristic of the initial design and functionality of computers.