LC-3 Virtual Execution

A virtual machine implementation based on the LC-3 (Little Computer 3) architecture, written in C.

Overview

LC-3 is an educational computer architecture for teaching assembly language programming. This VM executes LC-3 machine code by simulating the instruction set and memory model.

Features

• Complete LC-3 instruction set (16 opcodes)
• 8 general-purpose registers + PC + condition flags
• 65,536 memory locations (16-bit each)
• Memory-mapped keyboard I/O
• TRAP routines for system calls

Supported Instructions

Arithmetic & Logic

• ADD, AND, NOT

Control Flow

• BR (conditional branch), JMP, JSR/JSRR

Memory Operations

• LD, LDI, LDR, LEA, ST, STI, STR

TRAP Routines

• GETC, OUT, PUTS, IN, PUTSP, HALT

Building and Running

# Compile
mkdir build
cd build
cmake ..
cmake --build .

# Run a program
./vm-lc3 program.obj

Architecture

Registers

• R0-R7: General purpose registers
• PC: Program counter
• COND: Condition flags (N/Z/P)

Memory

• 65,536 x 16-bit locations
• Memory-mapped I/O at KBSR/KBDR

Example Program

.ORIG x3000
    LEA R0, HELLO
    PUTS
    HALT
HELLO .STRINGZ "Hello, World!"
.END

References

• LC-3 VM Tutorial