History of Programmable Logic — When did the first PLD (Programmable Logic Device) appear? Choose the most accurate time span based on industry milestones such as early PLAs (e.g., Intel 82S100 in the mid-1970s) and the first PAL families introduced soon after.

Introduction / Context:
The question tests basic historical awareness of programmable logic devices (PLDs). Understanding the timeline helps learners appreciate why PLDs, PALs, CPLDs, and FPGAs became dominant in digital design, replacing large amounts of fixed 7400-series logic with configurable alternatives.

Given Data / Assumptions:

• The earliest commercially recognized PLD/PLA devices emerged in the 1970s.
• PAL families followed shortly thereafter and catalyzed widespread adoption.
• Today's date is long after those introductions, so multiple decades have elapsed.

Concept / Approach:
We map well-known product introductions to decade markers. If foundational devices appeared in the 1970s, then relative to modern dates the elapsed time exceeds 40 years. Even conservative estimates (late 1970s or early 1980s) still cross the 40-year threshold by the mid-2020s for the earliest parts.

Step-by-Step Solution:
Identify earliest PLD era: mid-1970s for early PLAs and late-1970s for PAL families.Compute elapsed time: from 1975–1979 to the present exceeds 40 years.Compare to choices: 10, 20, 30 years are all less than the historical span.Therefore, select “More than 40 years ago.”

Verification / Alternative check:
Standard histories of digital logic show PLD roots in the 1970s, predating CPLDs (late 1980s) and FPGAs (mid/late 1980s). Thus, the >40-year answer is consistent with multiple independent references and industry retrospectives.

Why Other Options Are Wrong:

• More than 10 or 20 years: Far too recent; underestimates the technology's age.
• More than 30 years: Still less than the earliest introductions in the 1970s relative to today.

Common Pitfalls:
Confusing the first mass-market FPGAs (1980s) with the earlier PLD/PLA inventions; mixing up “first PLD” vs. “first FPGA.”

Final Answer:
More than 40 years ago