Understanding CGI (Common Gateway Interface): Which statement best describes CGI in the context of server-side web programming?

Introduction / Context:
Common Gateway Interface (CGI) is one of the earliest standards for dynamic web content. It defines how a web server launches external programs to process requests and how those programs communicate results back to the server and, ultimately, to the client.

Given Data / Assumptions:

• CGI specifies environment variables and I/O conventions.
• CGI programs can be written in many languages (C, Perl, Python, etc.).
• CGI programs execute as external processes, not inside the browser.

Concept / Approach:

With CGI, the server passes request data (query string, form inputs) to an executable program and captures its output (typically HTML) to return to the client. Language neutrality is a defining trait: any language capable of producing an executable or script that the OS can run may implement a CGI program.

Step-by-Step Solution:

Verification / Alternative check:

Check classic web server docs (for example, Apache httpd) that demonstrate CGI scripts written in Perl or compiled C programs, confirming language flexibility and process model.

Why Other Options Are Wrong:

SQL is not the defining interface; CGI is broader.

Options C/D describe plug-in or client-side execution models, which are incorrect for CGI.

Common Pitfalls:

Confusing CGI with server modules or with modern in-process frameworks; overlooking performance overhead of per-request process creation in classic CGI.

Final Answer:

An interface that accepts and returns data that may be written in any language that produces an executable file.