C Programming: Functions

• A function in C is a group of statements performing a task and a block of code executing a specific task.
• A function is also referred to as a method, subroutine, or procedure.
• Dividing the solution to a complex problem into functions makes it easier to understand and use.
• Functions can be either Standard Library functions or User Defined functions.

Declaring a Function

• Functions are declared using the syntax: return_type function_name( parameter list ) {body of the function}

Parts of a Function

• Return type refers to the data type of the value a function returns; can be void if nothing is returned.
• Function name refers to the actual name of the function, with the function name and parameter list together constituting the function signature.
• Parameters act as placeholders; when a function is called, a value is passed to the parameter, which is then referred to as the actual parameter or argument.
• Parameter lists refer to the type, order, and number of function parameters, with parameters being optional (i.e., a function may have none).
• Function body contains a set of statements defining what the function does.

Important Points About Functions

• Every C program must have a main() function that the operating system calls when the program starts.
• Every function needs to have a specified return type.
• Functions can return any type except arrays and functions.
• An empty parameter list in C means the parameter list is unspecified, and the function can be called with any parameters.
• In a C program, a function needs to be called before its declaration.

Parameters Passing

• An actual parameter is a parameter passed to a function.
• A formal parameter is a parameter received by a function.

Return statement

• A return statement terminates a function’s execution and returns a value to the calling function.
• After a return statement, program control passes to the calling function.