LC-3 Virtual Machine

A simple virtual machine implementation in C that simulates the LC-3 (Little Computer 3) architecture.

Overview

This project implements a functional LC-3 VM that can load and execute LC-3 machine code. It includes a complete instruction set implementation and debugging utilities.

Features

• 16-bit instruction set architecture
• 8 general-purpose registers (R0-R7)
• Program Counter (PC) and Condition Register (COND)
• Memory-mapped I/O
• Support for all LC-3 instructions:
  • Arithmetic: ADD, AND, NOT
  • Memory: LD, LDI, LDR, LEA, ST, STI, STR
  • Control: BR, JSR, JMP, RTI, TRAP
• Debug utilities for viewing memory and registers

Files

• vm.c - Main VM implementation
• vm_debug.c - Debug utility functions
• vm_debug.h - Debug function declarations
• prog.c - Example program generator

Compilation

Compile the VM:

gcc -Wall -std=c11 vm.c vm_debug.c -o vm

Compile the example program generator:

gcc -Wall -std=c11 prog.c -o simple_program

Usage

1. Generate a program file:

./simple_program

This creates simple_program.obj.

2. Run the VM:

./vm simple_program.obj

Output

The VM will display:

• Memory state after program load
• Memory state after execution
• Final register values

Architecture

The VM simulates:

• Memory: 65,536 addressable 16-bit locations
• Registers: 8 general purpose + PC + COND
• Instruction Format: 16-bit instructions with 4-bit opcode