How do you declare a function in C?

To declare a function in C, it is essential to specify the return type, function name, and parameters. This syntax provides the compiler with the necessary information to understand what the function is supposed to return and what arguments it will accept. The return type indicates what type of value the function will yield (e.g., int, float, void), the function name is how you will refer to it in your code, and the parameters (if any) specify the types and order of inputs the function requires.

For example, a function declaration might look like this:

int add(int a, int b);

In this case, int is the return type, add is the name of the function, and it takes two parameters of type int. This clear structure enables the function to be called properly elsewhere in the program.

The other options do not accurately reflect the standard method of declaring a function in C. Defining the function's body first, writing func followed by parameters, or placing the declaration at the end of the source file do not conform to the accepted syntax and would lead to compilation errors or confusion about the function's purpose and usage.