Final answer:
External devices that engage in I/O with computer systems are grouped into three categories: human readable, machine readable, and programmable.
Step-by-step explanation:
External devices that engage in I/O with computer systems are grouped into three categories: human readable, machine readable, and **programmable**. Programmable devices are those that can be programmed to perform specific tasks or functions by the user. These devices can be controlled and manipulated through software, allowing for customization and adaptability. The device that enabled digital computers to efficiently process large amounts of information is the hard drive. It's fundamental in the history of computing for its ability to facilitate quick access to large datasets, making modern computing tasks feasible.
An example of a programmable device is a microcontroller, which is a small computer on a chip that can be programmed to control various electronic systems. Another example is a programmable logic controller (PLC), which is commonly used in industrial automation to control machinery and processes. These devices enhance the versatility and functionality of computer systems by enabling users to define their own operations and automate tasks.