This handout is your reading assignment to go with H04.

• This handout presents a simplified version of a topic that is covered later in the Etter textbook (in Chapter 4)—namely the definition of simple functions.
• We are introducing this topic a bit earlier than in the Etter text, because it is so fundamental to Computer Science.
  • Computer Science is the study of algorithms and abstractions
  • A function definition involves both of these key concepts
  • It is, in a sense, an abstraction of an algorithm.
• The material on this handout should be all you need to complete H04.
  • However, if you want to read more about functions—though this is not required for now—you may like to read ahead in Chapter 4, particularly pages 156-160.
    

int xSquared(int x)
{
   return x*x;
}

• This function definition starts with int, because the instructions say it should return an integer value. On this assignment, your function definitions will always start with either int (if they are supposed to return a value that is an integer), or double (if they are supposed to return a value that is a real number that may have decimals.)
• The next thing that appears is the name of the function, in this case, xSquared
• What comes next is always a set of parentheses. What goes inside the parentheses is a list of parameters.
  • Parameters are special variables that are assigned a value when we call the function (the values that are assigned to these parameters are called arguments.)
  • For example, if we call the function by writing int y= xSquared(3); then 3 is the argument, and x is the parameter that will be assigned the value 3.
  • In this case there is only one parameter, namely x.
  • The variable name x is preceded by the type of x, which is int in this case.
• Then, we have a set of braces { }. These braces mark the beginning and end of the body of the function
• Since this function is a simple computation, we simply have the word return, followed by the formula for what we are trying to compute. On this homework assignment, all the function definitions will take this form.
• We need a semicolon at the end of the return statement, after the expression—and in this case that's the only semicolon we need.

  Please turn over for more
  

double xCubed(double x)
{
   return x*x*x;
}

double perimeterOfRectangle(double w, double h)
{
   return 2*w + 2*h;
}