Emulator: 16-bit Emulator & Integrated IDE

Emulator is a high-performance 8086/8088 CPU emulator and development environment built entirely in Swift and SwiftUI for macOS. It features a custom-built two-pass assembler, a memory-mapped VGA display, and a real-time instruction execution engine.

🚀 Features

🧠 CPU Core

• Full 16-bit Architecture: Implementation of the Intel 8086 instruction set.
• Register Suite: Accurate simulation of General Purpose (AX, BX, CX, DX), Index (SI, DI), Pointer (SP, BP), and Segment (CS, DS, SS, ES) registers.
• Flag Logic: Full support for Zero (ZF), Sign (SF), Carry (CF), Overflow (OF), and Auxiliary Carry (AF) flags.
• Interrupt System: Simulated BIOS (INT 10h, INT 16h) and DOS (INT 21h) API services.

🛠 Integrated Two-Pass Assembler

• Syntax Highlighting: Real-time code coloring for mnemonics, registers, and constants.
• Label Support: Sophisticated label resolution for loops (LOOP) and jumps (JMP, JE, JNZ, etc.).
• Memory Variables: Support for data definition directives (DB, DW) and bracket-based memory addressing (MOV AX, [VAR]).
• Procedure Logic: Functional CALL and RET mechanisms with stack management.

🖥 Virtual Hardware

• VGA Text Mode: Real-time rendering of the 0xB800:0000 memory segment (80x25 characters).
• Color Attributes: Support for 16-color foregrounds and backgrounds via the VGA attribute byte.
• Interactive Keyboard: BIOS-level keyboard buffer allowing user input to interact with running programs.
• Mode 13h Ready: Foundation for 320x200 256-color graphics.

🛠 Installation

1. Clone the repository:

   git clone https://github.com/AGaafar7/Emulator.git

2. Open Emulator.xcodeproj in Xcode 15+.
3. Select My Mac as the run destination.
4. Press Cmd + R to build and run.

📝 Usage Example: The "Typewriter" Program

Paste the following code into the built-in editor to test the keyboard and VGA synchronization:

; --- Setup Segments ---
MOV AX, CS
MOV DS, AX
MOV AX, 0B800H
MOV ES, AX
MOV DI, 0

; --- Main Interactive Loop ---
GET_KEY:
    MOV AH, 00H      ; BIOS wait for key
    INT 16H          ; Result returns in AL
    
    MOV AH, 0Eh      ; Yellow color attribute
    STOSW            ; Draw character and move cursor
    
    CMP AL, 13       ; Check if 'Enter' was pressed
    JE FINISH
    
    JMP GET_KEY

FINISH:
    HLT

🏗 Project Structure

• CPU8086.swift: The heart of the emulator. Contains the Fetch-Decode-Execute cycle and opcode switch.
• Assembler8086.swift: Logic for converting assembly text into machine code (Pass 1: Labels, Pass 2: Encoding).
• VGAView.swift: Optimized SwiftUI/Canvas view that renders the virtual memory segment as a visual screen.
• Registers.swift: Data structures for the 8086 register file and flag bit-masking.

🚧 Roadmap

• Implement full Mode 13h (320x200) Pixel Rendering.
• Add Hex Memory Viewer.
• Expand INT 21h for File System I/O.
• Step-by-Step Debugger with live register highlighting.

🤝 Contributing

Contributions are welcome! If you have optimized an opcode or added a new BIOS interrupt, feel free to open a Pull Request.

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Created by Ahmed Gaafar
Project started on March 27, 2026.