There are several advantages of using functions in C language:

1. Modularization: Functions allow you to divide a large program into smaller, more manageable pieces. This makes it easier to understand and maintain the program.
2. Reusability: Functions can be used multiple times in a program, which reduces the need for writing repetitive code. This saves time and effort and makes the program more efficient.
3. Improved readability: Functions make it easier to understand the purpose and functionality of a program. By breaking the program into smaller, more focused pieces, the overall structure and flow of the program becomes clearer.
4. Debugging: Functions allow you to isolate and debug specific parts of a program. This makes it easier to identify and fix errors in the program.
5. Extensibility: Functions allow you to add new functionality to a program without having to modify existing code. This makes it easier to update and expand the program as needed.

Overall, functions are a powerful and essential feature of C language that allow you to write more efficient, modular, and maintainable programs.