Microprocessors and DSPs vs. general digital systems What is the defining difference that sets microprocessor/DSP-based systems apart from other digital systems?

Introduction / Context:
Digital electronics spans a spectrum from fixed-function combinational/sequential logic to fully programmable computing cores. The key distinction for microprocessor and digital signal processor (DSP) systems is not merely speed or technology node, but the presence of a stored program that dictates behavior cycle by cycle.

Given Data / Assumptions:

• A “microprocessor/DSP system” executes instructions fetched from memory.
• “Other digital systems” may be hardwired logic with no instruction stream.
• Performance (speed) is not the primary defining characteristic in this question.

Concept / Approach:
Microprocessors and DSPs are general-purpose or domain-focused compute engines. They read instructions (opcodes) and data from memory, execute them in sequence (possibly with branching), and thus their function can be changed by altering the program. By contrast, fixed digital logic implements behavior directly in gates and flip-flops; altering behavior requires modifying the hardware or configuration bits (in PLDs/FPGAs), not an instruction stream.

Step-by-Step Solution:

Verification / Alternative check:
Consider reprogrammability: swapping firmware changes system behavior without changing hardware, which is unique to microprocessor/DSP architectures compared to fixed logic.

Why Other Options Are Wrong:

• A: Many digital systems do not execute instructions; they are hardwired.
• C and D: Speed does not define the category; some fixed-function logic outruns general-purpose processors.

Common Pitfalls:
Equating “digital” with “programmable”; many digital devices are not instruction-driven.

Final Answer:
The microprocessor follows a programmed sequence of instructions that the designer specified.