This program processes input lines using a multi-threaded pipeline consisting of four threads:

1. Input Thread: Reads lines from standard input.
2. Line Separator Thread: Replaces line separators (\n) with spaces.
3. Plus Sign Thread: Replaces every pair of plus signs (++) with a caret (^).
4. Output Thread: Writes processed data as lines of exactly 80 characters to standard output.

The threads communicate using producer-consumer buffers with mutual exclusion and condition variables.

To compile the program, ensure you have gcc installed on your system. Use the following command:

gcc -pthread -o line_processor line_processor.c