Instruction set categorization — which one is NOT an arithmetic instruction? Consider common assembly mnemonics used on microprocessors. Identify the instruction that is not arithmetic in nature.

Introduction / Context:
Classifying instructions by function helps predict effects on flags, register contents, and performance. Arithmetic instructions change numeric values, while rotate/shift operations manipulate bit positions without performing addition or subtraction.

Given Data / Assumptions:

• INC increments an operand by one.
• DEC decrements an operand by one.
• CMP performs a subtraction to set flags (no stored result), often considered arithmetic/compare.
• ROL rotates bits through the carry or within the word, depending on architecture.

Concept / Approach:

Arithmetic instructions like INC, DEC, ADD, SUB, and CMP act on numeric magnitude and modify arithmetic flags. ROL is a rotate operation (bit manipulation) and is categorized under shift/rotate, not arithmetic, even though it may affect flags such as carry or overflow depending on the CPU.

Step-by-Step Solution:

Verification / Alternative check:

Review architecture manuals (x86, ARM, 8051): rotate and shift opcodes are grouped separately from arithmetic/logic classes.

Why Other Options Are Wrong:

INC, DEC, and CMP are treated as arithmetic or arithmetic-related flag-setting operations in most ISAs.

Common Pitfalls:

Assuming CMP is purely logical because it does not store a result. It still performs an arithmetic subtraction to set flags.

Final Answer:

ROL (rotate left)