Computer Architecture - Control Unit and Instructions

Questions and Answers

What is the primary purpose of a computer instruction?

To specify a sequence of micro-operations for the computer. (correct)

To manage the hardware components of the computer.

To optimize the computer's performance.

To execute user-defined software applications.

Which of the following is NOT one of the three types of instructions in a basic computer?

Input-Output instructions

Arithmetic reference instructions (correct)

Memory reference instructions

In the instruction format for memory reference instructions, what does the 'I' bit indicate?

The mode of addressing: Direct or Indirect. (correct)

The size of the instruction in bits.

The type of opcode used in the instruction.

The priority level of the instruction.

What is the function of the control register in the instruction execution process?

To interpret and execute binary code instructions. Signup and view all the answers

Which part of a memory reference instruction specifies the actual memory location?

Address Signup and view all the answers

What is the maximum value of Opcode in a memory reference instruction?

7 Signup and view all the answers

What is indicated when the 'I' bit is set to 1 in a memory reference instruction?

Indirect addressing mode is utilized. Signup and view all the answers

How many bits are allocated for the Opcode in a memory reference instruction?

3 bits Signup and view all the answers

Study Notes

Control Unit Organization

Defines how the control unit supervises and coordinates the operations of the computer.
Essential for executing instructions by translating them into micro-operations.

Basic Concept of Instruction

A program consists of a sequence of instructions that dictate operations and operands for processing.
Each computer instruction is represented as binary code, stored in memory, and read into a control register for execution.
Instructions specify micro-operations that the computer follows for processing tasks.

Instruction Types

Three main types of instructions in a basic computer:
- Memory reference instructions
- Register reference instructions
- Input-output instructions

Memory Reference Instructions

Each memory reference instruction is formatted as 16-bits, consisting of:
- 1 Bit (I) indicating the addressing mode (Direct or Indirect)
- 3 Bits for Opcode, which specifies the operation
- 12 Bits for Address, which identifies the location in memory
Addressing modes:
- I = 0: Direct addressing mode directly uses the address provided.
- I = 1: Indirect addressing mode retrieves the address from another address in memory.
Opcode range is from 000 to 110, allowing for 7 distinct memory reference instructions.

Instruction Format Example

Mnemonic for AND operation:
- Description: AND operation will be executed with the contents of a specified memory location and the Accumulator (AC).
- Instruction code in Hex:
  - For Direct addressing (I=0)
  - For Indirect addressing (I=1)

Description

This quiz explores the organization of the control unit in computer architecture and its role in executing instructions. It covers instruction types, specifically focusing on memory reference instructions and their binary formatting. Test your understanding of how instructions dictate computer operations.