32-bit Processor Emulator

A complete implementation of a 32-bit processor emulator with assembler, virtual CPU, and instruction set architecture. Also includes a custom assembly language compiler and a fully functional CPU simulator that executes binary programs.

CPU Specifications

• Architecture: 32-bit register-based processor
• Registers: 4 general-purpose registers (A, B, C, D) + optional result register (R)
• Memory: Dynamic allocation with separate instruction and stack memory
• Stack: Grows downward from top of memory
• Instruction Pointer: Tracks next instruction to execute
• Status Codes: 8 different CPU states for error handling

Status Codes

Status	Description
cpuOK	Normal operation
cpuHalted	Program terminated normally
cpuIllegalInstruction	Unknown opcode encountered
cpuIllegalOperand	Invalid register or operand
cpuInvalidAddress	Memory access violation
cpuInvalidStackOperation	Stack overflow/underflow
cpuDivByZero	Division by zero attempted
cpuIOError	Input/output error

Instruction Set

Arithmetic Operations

Opcode	Mnemonic	Arguments	Description
0x2	add	reg	A = A + reg
0x3	sub	reg	A = A - reg
0x4	mul	reg	A = A * reg
0x5	div	reg	A = A / reg
0x6	inc	reg	reg = reg + 1
0x7	dec	reg	reg = reg - 1

Data Movement

Opcode	Mnemonic	Arguments	Description
0x9	movr	reg, num	reg = num
0xa	load	reg, num	reg = stack[D + num]
0xb	store	reg, num	stack[D + num] = reg
0x10	swap	reg1, reg2	Swap values of reg1 and reg2

Stack Operations

Opcode	Mnemonic	Arguments	Description
0x11	push	reg	Push register value onto stack
0x12	pop	reg	Pop value from stack into register

I/O Operations

Opcode	Mnemonic	Arguments	Description
0xc	in	reg	Read integer from stdin
0xd	get	reg	Read single character from stdin
0xe	out	reg	Write integer to stdout
0xf	put	reg	Write character to stdout

Control Flow

Opcode	Mnemonic	Arguments	Description
0x0	nop	-	No operation
0x1	halt	-	Stop execution
0x8	loop	label	Jump to label if C ≠ 0
0x13	cmp	reg1, reg2	R = reg1 - reg2
0x14	jmp	label	Unconditional jump
0x15	jz	label	Jump if R = 0
0x16	jnz	label	Jump if R ≠ 0
0x17	jgt	label	Jump if R > 0
0x18	call	label	Call subroutine
0x19	ret	-	Return from subroutine

Building

# Build with all features (default)
make

# Build standalone compiler
make compiler

# Build without bonus features
make cpu-basic

# Build with debug symbols
make debug

# Build optimized version
make release

# Clean build artifacts
make clean

# Show all available targets
make help

Running Programs

# Run a binary program with default stack (256)
./cpu run program.bin

# Run with custom stack capacity
./cpu run 512 program.bin

# Trace execution step-by-step
./cpu trace program.bin

CPU Registers

Register	Symbol	Purpose
A	A/0	General purpose, accumulator for arithmetic
B	B/1	General purpose
C	C/2	General purpose, loop counter
D	D/3	General purpose, base pointer for load/store
R	R/4/result	Result register for comparisons (BONUS_JMP)
SP	-	Stack pointer (internal)
IP	-	Instruction pointer (internal)

Memory Model

┌─────────────────┐ ← Memory start (address 0)
│   Instructions  │
│                 │
├─────────────────┤
│   Free Space    │
│                 │
├─────────────────┤ ← Stack limit
│                 │
│     Stack ↓     │
│                 │
└─────────────────┘ ← Stack bottom (highest address)

• Instructions: Loaded from binary file at start of memory
• Stack: Allocated at end of memory, grows downward
• Memory allocation: Dynamic, grows in 1024-word blocks as needed

License

This project is open source. Feel free to use and modify as needed.