Examples

1. Illustrating transfer of control:
   Examples: transferControl.c, bottles.c, morse.c (morse.c one passes values to functions, which we don't know about yet...)
2. Computing the square of a number: square.c

Why use Functions?

1. Avoid redundancy: write it only once. Makes maintenance easier, more efficient.
   1. E.g. use system's predefined functions: math.h, random number generator: random.c
   2. E.g. Help organize large programs: #include of your own stuff.
2. Miller's Magic number 7 +/- 2: Problem decomposition
   If this piques your interest, take a look at the original article:
   Miller, George A. 1956. The magic number seven, plus or minus two: Some limits on our capacity for processing information. Psycholgical Review 63: 81-97.

Syntax for function declaration and definition

1. A basic function:
        returnType FunctionName( parameterList...)
        {
             ... 
        }
2. Declaration: stating existance of function name, return type & parameter types (Just the "header")
3. Definition: The declaration plus the actual "guts" of the code (Includes the "body")
4. Position of declarations relative to main()

Enclosing scope

1. E.g. scope.cpp
2. Process: Draw enclosing boxes around each function, including main() and the entire program. When looking for a variable, look in the current box or outside the current box. You cannot look into another box.

Parameters

1. Passing in values using parameters
   E.g. Pass two numbers to a function to be added: parameters1.c
2. Call by value vs. call by reference
   1. Program to swap 2 numbers
      1. swap1.c: version in C++
         In C++ to have a parameter's changed value returned to the caller (i.e. it is a reference parameter), all that is needed is to put an ampersand '&' between the parameter type and the parameter name.
      2. swap2.c: version in C
         In C if you want a parameter's changed value to be reflected back to the calling program you must do the following three things:
         1. Call with an ampersand '&'
         2. Catch with an asterisk
         3. Use with an asterisk
            
   2. Confusing program dealing with parameters:
      1. version in C++: confuse1.cpp
      2. version in C: confuse2.c
         
3. Again consider the program parameters1.c that we looked at above. How would you change this to return the answer as a parameter rather than using the function's return value? Answer: parameters2

Storage classes: register, static, extern

Macro Substitution: #define for constants