22.3 Function Calls

Starting a program automatically calls the function named main (see The main Function). Aside from that, a function does nothing except when it is called. That occurs during the execution of a function-call expression specifying that function.

A function-call expression looks like this:

function (arguments…)

Most of the time, function is a function name. However, it can also be an expression with a function pointer value; that way, the program can determine at run time which function to call.

The arguments are a series of expressions separated by commas. Each expression specifies one argument to pass to the function.

The list of arguments in a function call looks just like use of the comma operator (see Comma Operator), but the fact that it fills the parentheses of a function call gives it a different meaning.

Here’s an example of a function call, taken from an example near the beginning (see A Complete Program).

printf ("Fibonacci series item %d is %d\n",
        19, fib (19));

The three arguments given to printf are a constant string, the integer 19, and the integer returned by fib (19).