Historically, when and where was the first commercial computer modem introduced for data transmission over telephone lines?

Introduction:
Modems (modulator–demodulators) enabled early digital computers to communicate over analog telephone networks by converting digital data into tones and back. The question targets historical context: the first widely recognized commercial computer modem introduced for such use.

Given Data / Assumptions:

• We focus on the first commercial, computer-oriented modem for data transmission over the public switched telephone network.
• We distinguish this from later standards and higher-speed devices.
• Dates refer to public availability/announcement rather than lab prototypes.

Concept / Approach:
Bell Labs/AT&T introduced the Bell 101 dataset modem in the late 1950s for 110 bit/s communications, followed by the Bell 103 (circa 1962) standard. The earlier device marks the first commercial instance for general computer data over phone lines.

Step-by-Step Solution:

Verification / Alternative check:
Industry histories consistently cite the Bell 101 (1958, USA) as the first commercial computer modem; Bell 103 standardized full-duplex 300 bit/s a few years later.

Why Other Options Are Wrong:

• 1963, USA: close but refers to later standards (e.g., Bell 103 era).
• 1965, Germany: later and different regional ecosystem.
• 1950, Japan: too early for a commercial computer modem on PSTN.
• None of the above: incorrect because 1958, USA is valid.

Common Pitfalls:
Confusing laboratory demonstrations with commercial availability; mixing up the first modem with the first standard widely adopted by hobbyists and businesses in the 1960s.

Final Answer:
1958, USA.