A function is a named, independent section of code that performs a specific task and optionally returns a value. The key components of a function are the function header, return type, name, parameters, body, local variables, statements, and returning a value. Recursion refers to a function calling itself directly or indirectly. Exercises include creating programs that use functions to calculate the average of integers, display text a given number of times, calculate the factorial of a number recursively and non-recursively.

1. Programming & Algorithm Functions & Procedures August 17, 2006

2. What Is a Function?

3. What Is a Function? A function is a named , independent section of code that performs a specific task and optionally returns a value to the calling program .

4. How a Function Works E.g.: PROGRAM function_illustration KAMUS function quadrate (x: integer) -> integer a, result: integer ALGORITMA input(a) result ← quadrate(a) output(result) function quadrate (x: integer) -> integer KAMUS LOKAL ALGORITMA -> x*x

5. How a Function Works

6. Writing a Function : PROGRAM function_illustration : : KAMUS : function quadrate (x: integer) -> integer : a, result: integer : : ALGORITMA : input(a) : result ← quadrate(a) : output(result) : {---------------------------------------------------------------------------------------------------------------} : function quadrate (x: integer) -> integer : : KAMUS LOKAL : value: integer : : ALGORITMA : value ← x * x; : -> value;

7. Writing a Function The function components: The Function Header [Line 12] The Function Return Type The Function Name The Parameter List The Function Body [Lines 18-19] Local Variables [Line 15] Function Statements [Lines 18] Returning a Value [Lines 19]

8. Recursion The term recursion refers to a situation in which a function call itself either directly or indirectly.

9. Exercises Create a program that inputs three integers and displays the average of them on screen. The program uses a function named average(). Create a program that inputs one integer (N) and display the words “I love C” N times. The program uses a procedure named I_love_C().

10. Exercises Create a program that inputs one integer (N) and displays the factorial of N on screen. The program uses a function named factorial(). Create the program number 3 using a recursive function named rec_factorial().