Among the following desktop database products, which one is <em>not</em> a relational database system in the conventional sense?

Introduction / Context:
PC-era databases evolved from flat-file and xBase systems to fully relational engines. Distinguishing which products implement relational features (tables with keys, joins, and relational operators) versus primarily flat-file or limited relational capabilities helps categorize legacy tools accurately.

Given Data / Assumptions:

• FoxPro and dBASE IV are xBase family products with relational features and SQL-like querying in later versions.
• 4th Dimension (4D) is a Macintosh-oriented relational database with a query engine and forms/reports.
• Reflex (an early Borland product) is best known as a flat-file, form/report-oriented database with limited relational functionality.

Concept / Approach:

A fully relational system supports multiple related tables, joins, and integrity constraints. Reflex operated largely as a single-table (flat-file) system with limited relation enforcement compared to the others. Thus, among the options, Reflex stands out as not being a conventional relational database system.

Step-by-Step Solution:

Verification / Alternative check:

Historical product literature and reviews characterize Reflex as a flat-file system; the others are documented as relational or having strong relational capabilities.

Why Other Options Are Wrong:

FoxPro/dBASE IV: Provide relational data handling and SQL-like commands.

4th Dimension: Designed as a relational DBMS for Macintosh platforms.

None of the above: Incorrect because Reflex does not qualify as a conventional RDBMS.

Common Pitfalls:

Assuming all database products of that era were relational; many were flat-file first with limited relational support.

Final Answer:

Reflex