Summary Programming Logic and Design Ch 9

Chapter 9

Name the parts of a method
 A program module that contains a series of statements that carry out a task
 Invoke or call a method from another program or method
 Any program can contain an unlimited number of methods
 Each method can be called an unlimited number of times
 Client- calling a program or method is called a method’s client
 A method must include:
 Method header (also called declaration or definition), includes identifying information
 Method body contains the implementation (statements that carry out the task)
 Method return statement- returns control to the calling method
 Local variables are declared in a method
 Keeping variables local helps them be more portable and less prone to error
 Global variables are known to all modules
 In scope, only recognised in a method


Design methods with no parameters
 When methods must share data
 Pass the data into and return the data out of methods,
 When you call a method from a program, you must know 4 things:
 What the method does, why are you calling the method
 Name of the called method
 Type of information to send to the method if any
 Type of return data to expect from any method if any




Design methods that require parameters
 Argument to the method- pass a data item into a method from a calling program
 Parameter to the method- method receives the data item
 When a method receives a parameter, you must provide a parameter list that includes:
 The type of parameter
 The local name for the parameter
 Signature- method’s name and parameter list
 Passed by value- copy of value is sent to method and stored in a new memory location
accessible to module
 The value remains unchanged in the main program even if it has been changed in the
module
 Each time a method executes, parameter variables listed in the method header are redeclared

,  myMethod (num myValue)
 Methods can require more than one parameter
 computerTax (num amount, num rate)
 List the arguments within the method call, separated by commas
 List a data type and local identifier for each parameter within the methods header’s
parentheses
 The data type must be repeated with each parameter
 Methods called, parameters have to be in the correct order, otherwise there will be logical
errors
 computerTax (num amount, num rate) cannot be called as computerTax (rate, amount)
 Arguments sent are called actual parameters
 Variables that accept the parameters in the method are called formal parameters


Design methods that return a value
 A variable declared within a method ceases to exist when the method ends (goes out of scope)
 To retain a value that exists when a method ends, return the value from the method back to
the calling method
 When a method returns a value, the method return type must match the data type of the value
that is returned
 Return type for a method
 Indicates the data type of the value that the method will send back
 Can be any type
 Also called a method’s type
 Listed in front of the method name when the method is defined
 Method can also return nothing
 Return type void
 Void method
 Example: num getHoursWorked (), returns numeric value
 Usually, you want to use the returned value in the calling method
 Not required Output “Hours worked is”,
 Store in variable or use directly without storing getHoursWorked ()
 Technically you are allowed to include multiple return statements in a method
 It’s not recommended
 Violates structured logic
 To use a method, you should know:
 What the method does in general
 The method’s name
 The method’s required parameters, if any
 The method’s return type, so you can use returned values appropriately
 Overhead refers to the extra resources and time required by an operation, such as calling a
method