Interface standards: RS-232 (Recommended Standard 232) defines electrical and signaling characteristics for which common PC interface?

Introduction / Context:
Many legacy peripherals communicated via standardized physical layers and signaling protocols. RS-232 is one of the most enduring standards, particularly in service, console access, and embedded applications.

Given Data / Assumptions:

• We are focusing on the PC context (COM ports).
• RS-232 specifies voltage levels, signal functions, and connector pinouts commonly associated with serial links.
• Parallel and game ports use different standards.

Concept / Approach:

RS-232 defines asynchronous serial communication, historically mapped to COM1/COM2 and presented on DB-25 or DE-9 connectors. It specifies line voltages (e.g., ±3 V to ±15 V), signal names (TXD, RXD, RTS, CTS, etc.), and basic timing for serial data exchange. Parallel ports follow IEEE 1284, and game ports use analog joystick interfaces unrelated to RS-232.

Step-by-Step Solution:

Verification / Alternative check:

Hardware manuals label DE-9 connectors as RS-232 serial ports; USB-serial adapters emulate RS-232 signaling for legacy equipment, confirming the association.

Why Other Options Are Wrong:

• Parallel port: Uses a different standard (IEEE 1284).
• Game port: Analog interface unrelated to RS-232.
• All of the above / None of the above: Both incorrect given RS-232’s clear scope.

Common Pitfalls:

Confusing connector shape with protocol; assuming DB-25 always equals RS-232 (it was also used for parallel on some systems).

Final Answer:

Serial port