CPU Emulator & Assembler

A custom CPU emulator with assembler/disassembler for the Dedinsky system programming course.

Quick Start

Build

mkdir build && cd build
cmake ..
cd ..
cmake --build build --preset debug    # Debug build
cmake --build build --preset release  # Release build

Usage

# 1. Assemble (.myasm → .bin)
./assembler program.myasm program.bin

# 2. Execute
./cpu_emulator program.bin

# 3. Disassemble (.bin → .myasm)
./disassembler program.bin
./disassembler program.bin output.myasm  # Save to file

Executables are in build/debug/ or build/release/.

Assembly Syntax

Numbers

• Only hexadecimal: 10 means 0x10 (16 in decimal)
• No 0x prefix: 0x10 will cause an error
• Valid examples: A, FF, 100

Labels

:main            ; Label definition
baw :main        ; Jump to label
cfn :function    ; Call function by label

Comments

mov x1, A        ; Load 0x0A into register x1

Instructions Overview

Basic Operations

• mov dst, src - Move value
• inp reg - Read hex from stdin
• out reg - Write hex to stdout
• hlt - Stop execution

Arithmetic

• add dst, a, b - Addition
• sub dst, a, b - Subtraction
• mul dst, a, b - Multiplication
• div dst, a, b - Division
• sqr dst, src - Square root

Control Flow

• baw addr - Branch always
• beq/beq/bgt/blt/bge/ble a, b, addr - Conditional branches
• cfn addr - Call function
• ret - Return

Stack

• str val, *addr - Store to stack
• ldr reg, *addr - Load from stack

Addressing Modes

Prefix	Meaning	Example
x	Register	x1 = register 1
*	Stack address	*100 = address 0x100
*x	Register indirect	*x1 = address in register 1

Registers

• x0-xf: General purpose (16 registers)
• x10: Program counter (rpc)
• x11: Base pointer (rbp)
• x12: Cycle counter (rcc)

Example Programs

Check examples/ directory:

• fibonacci.myasm
• iterative_factorial.myasm
• recursive_factorial.myasm
• stack_arithmetic.myasm

Project Structure

cpu_backend/     # Core emulator code
├── src/assembler/       # Assembler
├── src/cpu_emulator/    # CPU core
└── src/disassembler/    # Disassembler
examples/        # Sample programs
vendor/          # Dependencies (stack, exceptions)

Note: Numbers are always hexadecimal. 10 = 0x10 (16 decimal). 0x10 will cause an error.