The correct answer is option 'D' - ENIAC.

- ENIAC stands for Electronic Numerical Integrator and Computer. It was the first electronic digital programmable computing device.
- ENIAC was developed by J. Presper Eckert and John W. Mauchly at the University of Pennsylvania in the United States during World War II.
- The main purpose of ENIAC was to perform complex calculations for military purposes, such as artillery trajectory calculations.
- ENIAC was a massive machine that occupied a large room and consisted of approximately 17,468 vacuum tubes, 7,200 crystal diodes, 1,500 relays, 70,000 resistors, 10,000 capacitors, and 5 million soldered joints.
- It was programmed using a combination of patch cables and switches. The programming process was time-consuming and required physically rewiring the machine to change the program.
- ENIAC was capable of performing addition, subtraction, multiplication, and division operations, as well as more complex calculations using its stored program.
- It had a speed of about 5,000 operations per second, which was significantly faster than previous computing devices.
- ENIAC was used for various calculations during its operational period, including calculations for the hydrogen bomb, weather prediction, and atomic energy research.
- Despite its groundbreaking capabilities, ENIAC had some limitations. It was not a stored-program computer, meaning that its program had to be physically reconfigured each time it needed to be changed. It also required a large amount of electricity and generated a significant amount of heat.
- ENIAC paved the way for the development of modern computers and is considered a landmark in the history of computing.

In conclusion, ENIAC was the first electronic digital programmable computing device, making option 'D' the correct answer.