8085 microprocessor — functional blocks: Within the 8085 CPU, the sub-block responsible for arithmetic and logical operations (add, subtract, AND, OR, compare) is called the __________.

Introduction / Context:
Microprocessors are built from several cooperating blocks. Understanding which block does what helps when studying instruction execution and troubleshooting at the register/flag level. In the Intel 8085 (and most CPUs), arithmetic and boolean operations are concentrated in a single module.

Given Data / Assumptions:

• Target device: Intel 8085 microprocessor as a representative 8-bit CPU.
• Operations of interest include arithmetic (add, subtract, increment) and logic (AND, OR, XOR, compare, rotate).
• Flags (e.g., zero, carry) reflect ALU results.

Concept / Approach:
The Arithmetic Logic Unit (ALU) executes integer arithmetic and bitwise operations and sets condition flags. The Control Unit sequences fetch/decode/execute; registers hold operands and results; buses move data and addresses. Together they form the CPU, but the ALU specifically performs the calculations asked in the prompt.

Step-by-Step Solution:

Verification / Alternative check:
8085 block diagrams show the ALU connected to the accumulator and temporary registers, with status flag logic attached. Instruction manuals describe ALU actions per opcode.

Why Other Options Are Wrong:

• CPU: Too broad; encompasses ALU plus control and registers.
• I/O: Handles external interfacing, not arithmetic/logic.
• bus decoder: Not a standard 8085 block name for ALU functions.
• flag controller: Flags reflect ALU outcomes; they do not compute results.

Common Pitfalls:
Using “CPU” and “ALU” interchangeably; forgetting that flags are a consequence of ALU operations, not a separate arithmetic unit.

Final Answer:
ALU