In C programming, a function is a block of code that performs a specific task and can be called or invoked from other parts of the program. Functions provide modularity, reusability, and better code organization by breaking down complex programs into smaller, manageable units. Here's a detailed explanation of functions in C along with examples: 1. Function Declaration:    A function must be declared before it is used. The declaration specifies the function name, return type, and the types of parameters (if any) that the function accepts. It typically appears before the main function or in a header file.    Syntax:    ```c    return_type function_name(parameter1_type parameter1, parameter2_type parameter2, ...);    ```    Example:    ```c    int add(int num1, int num2); // Function declaration    ``` 2. Function Definition:    The function definition contains the actual implementatio...