macOS Calculator App in Pure C with No Bundle or Plist Required

Overview

A working calculator application built in pure C using Cocoa via objc_msgSend and the Objective-C runtime—without using Objective-C language syntax and without requiring macOS bundle or plist files.

This project demonstrates:

• GUI development outside Xcode in pure C (applicable to any systems language)
• Native macOS menu bar support without bundle/plist (contrary to common misconceptions online)
• Direct Cocoa integration using only the Objective-C runtime introspection API

Features

• Calculator UI with 16 buttons (0-9, +, -, *, /, =)
• Display field showing arithmetic results
• Working operations: +, -, *, /
• Native menu bar with Cmd+Q to quit (no bundle required)
• Window close button to exit

Building

Both single executable and app bundle approaches work:

Single Executable (Recommended)

./build.sh
./calculator

Or launch via Finder/Dock:

open calculator

Manual Compilation

gcc -o calculator calculator.c -framework Foundation -framework AppKit -lm
./calculator

As an App Bundle (Optional)

If you prefer the app bundle experience:

mkdir -p Calculator.app/Contents/MacOS
gcc -o Calculator.app/Contents/MacOS/calculator calculator.c -framework Foundation -framework AppKit -lm
open Calculator.app

Technical Details

Implementation

• Uses objc_msgSend() for all runtime method calls
• Dynamically creates delegate classes for window and button events
• No Objective-C language features—pure C with runtime introspection
• Handles ARM64 and x86_64 calling conventions for objc_msgSend

Menu Bar Without Bundle

The key insight is that macOS doesn't require a .app bundle to display the menu bar. The app simply needs to:

1. Set an app delegate before calling finishLaunching()
2. Create UI during the applicationDidFinishLaunching: callback (not after)
3. Call activateIgnoringOtherApps: for immediate foreground rendering
4. Enter the event loop with run()

This contradicts the common misconception that bundles are essential for menu visibility.

Project Context

This started as a learning exercise in:

• Using Amp Free with the Beads issue tracker for the first time
• Building a macOS GUI entirely in C outside the Xcode ecosystem
• Proving that bundles/plists are not technically required for visible menus (despite online claims to the contrary)

The result is a minimal proof-of-concept showing that modern macOS app development can happen outside Xcode, in pure C, with full native UI integration.

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Made with Amp Free and Beads

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