GTK Calculator

A lightweight desktop calculator built in C with GTK+ 3. The app supports expression input through on-screen buttons, high-precision arithmetic via bc -l, and a built-in calculation history panel.

Screenshot

Features

• GTK+ 3 desktop UI with a compact keypad layout
• Expression evaluation through bc -l for floating-point math
• Calculation history view with separate history clear (CH)
• Input controls: clear (C), backspace (⌫), parentheses, decimal support
• Error handling for invalid expressions (shows Error in display and history)

Tech Stack

• Language: C
• UI Toolkit: GTK+ 3
• Evaluator: bc
• Build System: GNU Make + pkg-config

Requirements

Install the following before building:

• gcc
• make
• pkg-config
• GTK+ 3 development packages (gtk+-3.0)
• bc

Example (Debian/Ubuntu):

sudo apt update
sudo apt install -y build-essential pkg-config libgtk-3-dev bc

Build and Run

From the project root:

make
./calculator

Available Make Targets

make           # build
make clean     # remove object files and binary
make install   # install binary to /usr/local/bin (sudo required)
make uninstall # remove binary from /usr/local/bin (sudo required)

Controls

• Digits: 0-9
• Operators: +, -, *, /
• Grouping: (, )
• Decimal point: .
• =: evaluate current expression
• C: clear current input
• ⌫: delete last character (UTF-8 safe)
• CH: clear history panel

Project Structure

calculator/
├── main.c      # GTK UI, button actions, expression evaluation, history handling
├── Makefile    # build/install/uninstall targets
├── preview.png # application screenshot
└── .gitignore

Notes

• Expression results come from bc -l, so behavior follows bc arithmetic rules.
• The entry widget is intentionally read-only; inputs are driven by button clicks.