UPC Barcode Generator

This C program generates a UPC-A barcode and displays it using the X11 library on macOS or Linux. The program uses no third-party libraries and follows the UPC-A encoding format as per GS1 standards.

Features

• Generates UPC-A barcode with 12-digit input.
• Displays the barcode using X11 (XQuartz for macOS).
• No external libraries are required beyond X11.

Prerequisites

• XQuartz (for macOS) or X11 (for Linux).
• X11 development libraries.

Compilation

You can compile the barcode.c file using the following command:

gcc -o barcode barcode.c `pkg-config --cflags --libs x11`

Usage

Once compiled, run the program by passing a 12-digit UPC-A code as an argument:

./barcode 036000291452

This will display the barcode for the given UPC-A code in an X11 window.

Structure of UPC-A Barcode

• A UPC-A barcode is 12 digits long.
• It includes left and right guard patterns, center guard, and the encoded digits.

Guard Patterns

• Left Guard: 101
• Center Guard: 01010
• Right Guard: 101

Encoding

Each digit is represented by a 7-bit binary pattern. The left and right sides use different encodings:

• Left side encoding: Odd parity.
• Right side encoding: Even parity.

Notes

• The program does not validate the check digit, but UPC-A barcodes typically use a checksum to ensure data integrity.
• Ensure that XQuartz or X11 is running before executing the program.