Programming languages: Which option represents a non-standard, incorrect spelling/variant of a well-known computing language name?

Introduction / Context:
Several classic languages have precise names and spellings. Using the wrong character can change meaning or indicate a non-standard, unofficial variant. This question targets a common confusion between a digit and a letter in a language name.

Given Data / Assumptions:

• We compare options against established, standardized language names.
• We look for a non-standard version or incorrect form.

Concept / Approach:

IBM’s language is officially named PL/I (Programming Language One), where the final character is the uppercase letter 'I', not the digit '1'. Writing 'PL/1' with the numeral 1 is a widespread but non-standard misprint and therefore represents a non-standard version of the name.

Step-by-Step Solution:

Verification / Alternative check:

IBM documentation, standard texts, and compilers uniformly use PL/I. The roman numeral I denotes “one.”

Why Other Options Are Wrong:

• APL: A Programming Language—standard name.
• PROLOG: logic programming language—standard name.
• ARMY: not a recognized mainstream language name in this context; however, the specific target of 'non-standard version' is the incorrect spelling of PL/I.
• None of the above: incorrect because PL/1 is indeed a non-standard spelling.

Common Pitfalls:

• Overlooking typographical details (letter I vs. numeral 1) that change correctness.

Final Answer:

PL/1.